【 Weak current College 】 IP network of multimedia communication technologies---Power By 【 China power house network 】

1 preface
At the turn of the century, mankind into the information and network era, the national information infrastructure (NII) has become the world information technology development strategy objectives. LAN, Intranet and Internet have been extraordinary development. Which entered since the mid-1990s, Internet traffic by 300% per year in the growth rate, according to the forecast AT & T, 2001 Internet traffic will be balanced with the telephone network.
At the same time, the IP network for multimedia communication demand expansion. Therefore, the International Organization for Standardization, such as ITU, ETSI, IETF, IMTC etc are multimedia communication standards focus shifts to IP network-based multimedia communication system standards. For example, the H.323 standard ITU-T.
H.323 is an International Telecommunication Union (ITU), a standard recommendation H.323 family, where V1 in 1996 by ITU study group 15, currently SG-16 has just completed the latest version of H.323 V2 development work, and was adopted. H.323 developed no QoS (quality of service) guarantees packet network PBN (Packet Based Networks) on standard multimedia communication system. These packet networks dominate today's desktop network system, including TCP/IP, IPX packet switched Ethernet, fast Ethernet, token ring, FDDI technology. Therefore, the H.323 standard for LAN, MAN, Intranet, Internet, multimedia communications applications provides the technical infrastructure and security.
H.323 is a series of standards for multimedia communication ITU-T H.32X part of series of standards makes existing communication network for video conferencing. Which is in the H.320 N-ISDN on standard multimedia communication; H.321 is carried out on the B-ISDN multimedia communication standards; H.322 is QoS LAN on standard multimedia communication; H.324 is in PSTN and wireless networks for multimedia communication standards. 2 introduction to H.323 standard
H.323 standards including a non-QoS packet network for multimedia communication skills required. These packet networks including LAN, MAN, Intranet/Internet as well as the use of PPP, such as grouping agreement through the PSTN or ISDN dial-up connection or a point-to-point connection.
H.323 is a network-based communication system defines four main components: Terminal, gateway, gateway, multipoint control unit (MCU).
1) Terminal (Terminal): PBN can provide real-time, in a two-way communications device nodes. Figure 2 describes its composition. All terminal must support voice communications, video and data communication is optional. H.323 defines different audio, video and/or data terminal together the required mode of operation. It is the next generation Internet phone, audio conferencing Terminal and the main video conference technology.
All H.323 terminals must also support standard for H.245, H.245 control channel usage and channel performance. In H.323 Terminal optional component is image codec, T.120 data conferencing protocols and MCU function.
2) gateway (Gateway): H.323 conferencing system of an option. Gateway offers many services, including H.323 Conference node equipment and other ITU standard compatible terminal between the conversion function. Such features include transmission format (such as H.225.0 to H.221) and communication procedures of conversion (such as H.245 to H.242). In addition, the PBN-and circuit-switched network between the SCN, gateway also performs voice and image codec conversion, as well as the call setup and clearing function. Figure 3-Schematic of a H.323/H.320 gateway. Terminal use H.245 and H.225.0 protocol to communicate with the gateway.
The use of appropriate decoder, H.323 gateway can support H.310, H.321, H.322 and V.70 standard terminal.
3) gateway (Gatekeeper): perform two important call control features. The first is address translation function, defined in the RAS. For example, the Terminal and the gateway of PBN alias translation into IP or IPX address; the second is the bandwidth management function, RAS also defined. For example, a network administrator can define PBN simultaneously meeting the threshold of the number of users, once the user number of the set value, the gateway will reject any more than the threshold value of the connection request. This will make the entire Conference of bandwidth in the network to a total bandwidth to the extent feasible, the remaining portion is reserved for E-MAIL, file transfer and other PBN Protocol. Gateway's other features may include access control, call validation, gateway, location, etc.
Management by a single gateway to all Terminal, gateway and multipoint control unit of collection, we refer to as H.323.
While logically, gateway and H.323 nodes device is detached, but producers can gateway functionality into H.323 Terminal, gateway and multipoint control units, and other physical device.
4) multipoint control unit (MCU): MCU support three or more nodes in the device. In H.323 systems, an MCU consists of a multipoint controller MC (required) and a few more processor MP, but also can not contain MP. MC processing terminal control information between H.245 and decide it on the video and audio in General. If necessary, MC can also determine which video stream and an audio stream needs to be multicast to control conference resources.
MC does not deal directly with any media information flow, and it is left to the MP. MP on audio, video and/or numberAccording to the information to be mixed, switching and processing. MC and MP can exist within a special equipment or as part of other H.323 components.
5) multipoint meetings: in the standard, H.323 multipoint implementations there are different ways and configured into a centralized, distributed and mixed meeting.
* Centralized multipoint Conference (Centralized): requires an MCU to organize a multipoint session. All Terminal to an ad hoc manner to the MCU sends video streams, audio streams, data flow and control flow.
* Distributed multipoint Conference (Decentralized): use multicast (Multicast) technology. Participation in meetings of H.323 Terminal to the other participating Terminal multicast video and audio information without having to send to the MCU. Note: multiple points of data control is still carried out centrally by the MCU, H.245 control channel information also continues to point to point transmission to the MC.
* Hybrid multipoint Conference (Hybrid): centralized and distributed feature combinations. H.245 signaling and video streams (or audio stream) point-to-point transmission to MCU. The remaining signal (video or audio) to multicast transmission to attend the meeting of H.323 Terminal.
* H.323 support mixed multipoint Conference (Mixed), some terminal in centralized meeting other Terminal in distributed meetings, and MCU bridging two meetings. Terminal do not need to know the meeting of the mixed attribute, just understand it to send and receive information is session mode.
Multicast allows more efficient use of network bandwidth, but increases the load on the terminal's calculation. Terminal switch needs to be mixed, they receive a video stream and an audio stream. In addition, network switches and routers must support multicast.
H.323 limited to each multipoint session only one MC's network structure. Although, in theory, the number of participants in the meeting can be a lot, but people will notice: when the number of participants met or exceeded the 10-20, the result is not satisfactory. 3 H.323 communication stack
H.323 system communication can be seen as video, audio, and control information.
1) system control: System control function is the core of H.323 Terminal, it provides H.323 Terminal to the proper operation of the signalling. These features include call control (construction and dismantling), the ability to switch, the command and direct the signalling as well as for opening up and description logic channel content of message, etc. The entire system of control by H.245 control channel, H.225.0 call signaling channel and RAS channel.
2) grouping and synchronization: H.225.0 standard describes no QoS guarantees LAN media streaming Pack grouping and synchronous transmission mechanism. H.225.0 on transmission of video, audio, data and control flow is formatted for output to a network interface, also from the network interface to enter text in the compensation received for video, audio, data and control flow. In addition, it also complete logic into frames, order number, error correction and error detection capabilities.
3) audio: audio signal contains digitized and compressed voice. H.323 supported compression algorithms are in line with the ITU standard. For speech compression, H.323 terminal must support the G.711 voice standards. Support other standards, such as the ITU G.723.1, G.729.A is optional.
4) video: Although the video feature is optional, but any H.323 terminal of a video feature must support the H.261 codec standards; supports H.263 standard is an optional feature. H.261 standard use P * 64Kb/s (P = 1, 2, ... 30) channel for communication. Used to improve the image quality by moving the compensation is an optional feature H.261. H.263 backward compatible with standard, H.261 because 1/2 pixel mobile estimation techniques, forecasting, and optimization of the low rate of frames transferred by Hoffmann (Huffman) encoding table, H.263 picture quality is greatly improved.
5) T.120 data: the data session is an optional feature. When supporting data, the data session for collaborative work, such as whiteboard, application sharing, file transfer, static image transmission, database access, audio, video conference, etc. 4 IP network for multimedia communication
In H.323 multi-media communication system, the signalling and control the flow of data is transferred using a connection-oriented transport mechanism. In IP protocol stack, IP and TCP collaborate to complete the connection-oriented transport. Reliable transmission guarantees that the data packets of a flow control, continuity and accuracy, but this may cause a delay and consume network bandwidth. H.323 is a reliable TCP for H.245 control channel, T.120 data channel, call signaling channel.
While the video and audio information using unreliable, object-oriented non-connected transmission mode that uses the User Datagram Protocol UDP (User Datagram Protocol). It cannot provide excellent QoS. UDP only provide minimal control information, therefore, relatively small TCP transmission delay. H.323 is an unreliable UDP is used for video, audio, and RAS channel.
There are multiple video and audio streaming of multimedia communication system, based on UDP not reliable transmission using IP multicast, and real-time Transport Protocol from the IETF RTP (Real-Time Protocol) processing of video and audio information. IP multicast is a UDP mode is not reliable Multicast Transport Protocol. RTP in IP multicast for the top level for IP network video and audio stream. Each UDP packets are coupled with a time-scale and number of the header. If the receiver is equipped to fit the buffer, it can take advantage of the time-scale and serial number information "recovery, recycling" packet, records of sequence package, synchronous voice, video and data, and to improve the effectiveness of continuous replay.
RTCP real time control protocol (Real-Time ControL Protocol) is used for the control of RTP. RTCP monitoring service quality as well as online shipping information, and will contain information about the service quality control information package circulated to all communications node.
Since H.323 based on RTP/RTCP, therefore it can be Internet multicast backbone (IMB-Internet\'s Multicast Backbone), has multicast capabilities of the Internet to run virtual online, as well as support for audio, video and data of multimedia communication.
In a large packet networks, such as Internet, Intranet, as a multimedia call retain sufficient bandwidth is very important and difficult. Another IETF protocols: RSVP (Resource Reservation Protocol: RSVP) allows the receiver to a particular data stream for a certain amount of bandwidth, and whether the application is permitted to reply. Although the RSVP is not a formal part of H.323 standard, but most of the H.323 products must support it because the bandwidth reserved for IP network is critical to the success of multimedia communication. RSVP required Terminal, gateway, equipped with more processor MCU and intermediate routers or switches support. 5. concluding remarks
On a world scale information network technology development trend, multimedia communications will be the "information superhighway" main communication business, but also the future direction of communication development. With LAN, Internet, Intranet in the world of rapid development, and growth, based on the IP network for multimedia communication is imperative, cheap and features increasingly powerful computer-based H.323 V2 terminal will eliminate expensive H.320 Terminal. In view of this situation, the world famous computer, network, communication equipment, video conference system manufacturers have multimedia communication terminal/system development focused on positioning in H.323-based IP networks V2 Terminal/system.
At present, China is building a large scale "169 China public multimedia communication network" and it is IP Over ATM-based packet network of the H.323 V2 multimedia communication terminal/system in China will be promising and will be China's "national information infrastructure (NII) play an extremely important role. Perhaps, our communication equipment manufacturing industry can "169 China public multimedia communication network" construction as an opportunity to intensify the design, development, production, sales, based on the H.323 V2 standard IP multimedia communications terminals and systems, enabling our emerging multimedia communication devices on the market.

【 Weak current College 】 how to select the low-frequency speaker in.. ---Power By 【 China power house network 】

First: the choice of low-frequency speaker:
A speaker Shelf has two kinds: 1 is: plate punch made of 2 is: HI--FI and gold round cast shelf, advantages: good rigidity,
B: voice coil choices: 1. wire-wound, 2: oxygen-free copper wire wound, 3: flat enamelled wire wound, 4: drill magnesium alloy construction, 5: KAPTON of polymer material, the material used for the aviation industry can withstand the high temperature of 350 degrees centigrade,
C: speakers lead selection, 1: stranded copper braided cord, 2: quality silver coated copper wire
D; The select 錐: bevel-is the main vocal component speakers, its materials as: geometric shape and processing production process on the low frequency range of frequency response and sound effects, also decided that the distortion of the low-frequency speaker cell size, 1: from widening the playback frequency range of hair, bevel-effective high-elastic material, 2: low-frequency speaker distortion reduction from the point of view, bevel-materials with good steel, 3: from the lower bevel-split vibration q value perspective. bevel-material has a large internal loss, bevel-material is divided into 1: natural low pulp salvage, 2: paper cones, 3: polymer composites, such as,: graphite reinforced polypropylene braided carbon fiber-4: wool, paper trays,
E,: speaker resonance frequency and quality factors, 1: lower resonance frequency, low frequency emphasis put sound limit can do much more low-frequency response, it is often the better, because the speaker resonance frequency and speaker vibration system of equivalent quality and resistance is proportional.
How to choose

Both hands and gently press the speaker cones, pressing the more feel soft and shows when the speakers fold ring and centering force more soft, it slices the resonant frequency is low, in short, the low-frequency speaker of the lower resonance frequency, the better, 2: speaker quality factor: usually choose quality factor: 0.4---0.5.

【 Weak current College 】 streaming media technology principle and play mode-Power By 【 China power house network 】

First, the principle of streaming media technology
Streaming implementations need to cache. Because the Internet is based on the packet transmission for disjoint asynchronous transfer, on a live A/V source or storage of A/V files, they are in transit is broken down into many packages, since the network is dynamic, various package selection, the route may vary, they reach the client's time delay would not, even the first packet is also possible after arrival. To do this, use the cache system to compensate for the delay and jitter, and packet in the correct order, so that the media data can be continuously output, not because the network is temporarily congested to play there. Usually cache capacity is not required because the cache using a circular linked list data structure to store: by discarding has played content, flow can reuse empty out of cache space to cache the content of the follow-up is not playing.
Streaming requires the appropriate transport protocol. Since TCP requires more overhead, so it is not suitable for the transmission of real-time data. In streaming implementation scenarios, generally use HTTP/TCP to transfer control information, and RTP/UDP to transfer audio data in real time.
Streaming process generally goes like this: the user to select a top media, Web browsers and Web servers using HTTP/TCP exchange control information, so that the required transmission of real-time data to retrieve from the original information; then the client's Web browser to start A program, use the/VHelper HTTP retrieval from a Web server related parameters on Helper program initialization. These parameters may include directory information, A/V data encoding type or with the A/V retrieval server address.
A/VHelper program and A/V server running real-time streaming protocol (RTSP), in exchange for A/V transmission required control information. And CD players or VCRs provides functionality similar to the RTSP provides control playback, fast forward, fast reverse, pause, and record commands. A/V Server using RTP/UDP protocol to A/V data is transferred to the A/V client (usually think customer program is the equivalent of a Helper program), once A/V data arrives at a client, A/V customer program to play the output.
It is important to note that in streaming, using RTP/RTSP/UDP and TCP are two different communication protocols and A/V Server networking is to enable the server to redirect output to a different than running A/client VHelper program is intended to address. Implement streaming generally require a dedicated server and player.
Second, the way streaming media playback
1. unicast
Client and media server requires a separate data access from one server to send out each packet can only be delivered to a client, this way is called unicast transmission. Each user must send to the media server, a separate query and media server must be sent to each user of the application a copy of the packet. This huge redundancy first heavy burden caused the server to respond to the need for a long time, or even stop playback; managers are forced to buy hardware and bandwidth to ensure a certain quality of service.
2. multicast
IP multicast technology to build a network with multicast capability, allows the router to a packets to multiple channels. Using multicast mode, a single server to hundreds of thousands of clients at the same time send a continuous stream of data without delay. Media Server only needs to send a packet, instead of multiple; all the requesting client to share the same packet. Information can be sent to any address of the client, reduce the network transfer the total amount of packets. Network utilization efficiency is greatly improved, costs are reduced.
3. on-demand and broadcast
On-demand connection is a client-server proactive connection. In on-demand connections, users select the content item to initialize the client connection. Users can start, stop, rewind, fast forward, or pause the stream. On-demand connections provide maximum control of convection, but this way because each client's respective connected server, but will quickly run out of network bandwidth.
Broadcasting means users passive reception. In broadcasting, the client receiving the stream, but cannot control the flow. For example, the user will not be able to pause, fast forward or rewind the stream. Broadcast packets in a separate copy will be sent to all users on the network. Use unicast for sending packets that need to be copied multiple copies multiple point-to-point way both to those users that need it, and send using broadcast, a copy of the individual data packets are sent to all users on the network, regardless of whether the user is needed, the above two transmission modes would be a waste of network bandwidth. Multicast incorporates both outgoing strengths to overcome these weaknesses in the way of sending a packet of separate a copy sent to the needs of those customers. Multicast will not replicate multiple copies of data packets to the network, do not send the packet to those customers who require it to ensure that the network multimedia applications consume network bandwidth of minimum.

【 Weak current College 】 Stadium sound reinforcement system construction of small problems

Design is a prerequisite for the construction, construction will provide feedback to the design, make the design more reasonable. Will now be in the design and construction of the problems encountered and lessons learned with our audio enthusiasts share, anomalies please correct me.
1. speaker layout and sizing
According to the architectural characteristics of the venues, the main function of the purposes and characteristics of the integrated speakers, consider layout mode.
Stadium speakers use a decentralized layout, the benefit is more uniform distribution of the acoustic field, there is no acoustic shadow area, the sound reaches the audience's time, there is no delay sense; in addition the audience can get more direct access to sound, the reverberation time of sound field in beneficial to increasing clarity. Speakers choose better directivity Horn speakers, conditions allow it can also select the linear array.
Stadium Speaker layout mode is more flexible, decentralized, centralized and hybrid variety. Centralized sound reinforcement can effectively avoid multiple speaker voice interaction, will also help to improve the consistency of acoustic phase. Speakers to use power point remote speaker so that the audience gets direct access to as much as possible. Mixed layout can be decentralized and centralized or decentralized local concentration as a whole. No matter what kind of layout, ultimately to achieve increased direct sound, improve clarity of purpose.
2. construction
2.1 laying cables
1) cable laying often and construction, decoration and other departments to cooperate with the opportunity of choosing a laying.
2) system in the laying of cable ends to leave enough margin, Ning long not to short to avoid late-stage construction of the extension cable is too short.
3) it is necessary to pay attention to the protection of the line pipe, especially the ground laying of the pipeline, to tape bandage its interface, avoid cement and other sundries. To prevent vehicle nianzha damage, necessary to put the line pipe buried underground. Line pipe outlet mouth to mouth on plastic protector. Bending steel pipe, be careful when using specialized tools for bending multiple times in order to avoid dead corner and broken.
4) cable tray installation has to be beautiful, and detours.
5) cable ends to timely placement of labels to find.
6) cable show line pipe or cable tray, to be used in fabric package maximum protection to avoid missing or defaced.
2.2 speakers of hoisting
1) speaker installation angle according to the design requirements, and repeatedly adjusted, it is necessary to be able to cover the entire Auditorium, but also to guarantee the uniformity of the sound field. In the entire system after installation, the instruments and listen to the sound of lifting angle for further adjustments.
2) Auditorium is the main sound reinforcement area, competition venues of sound reinforcement characteristics indicators can be used with a sibling or reduce a Auditorium.
3) Stadium Speaker hoisting points are often high off the ground, so during the installation process, be sure to fasten your seat belt, and ensure personal safety. On the appointment, tools and other debris not misplaces, avoid falling.

2.3 insert installation
1) rostrum, judge seats and Stadium venues around usually has a microphone jack, these ground socket for the bottom box installation height slightly below the floor or ground, so that the box has more space.
2) to pay attention to the orientation of the plug and the bottom box into line direction, try to make beautiful, symmetrical.
3) from the line pipe outlet outlet to the cartridge to use hoses and fittings, and bandaging, prevent metal cut cable.
4) bottom box installed before installing and plugged in, you want to install the closure plate seal, prevent debris entering.
2.4 peripheral equipment installation
1) devices before installation, first to the laying of cable, to ensure that all normal checks and no short circuit or open circuit, the subject line intact.
2) equipment cabinet installation construction by a figure, as far as possible ensure that the quality of the arrangements in the following; minimize connection cable length and cross-device to have a reasonable interval, is conducive to the heat and balanced appearance.
3) lines that all equipment, including the power cable, signal cable, speaker cables and the control line, etc., to fixed online tank or cabinets, both beautiful and strong, and left margin to convenient pluggable. Equipment and cable ends to affix a specialized label, easier to find.
2.5 other considerations
1) all equipment, cable's certificate, instructions, warranty cards, as well as spare parts to keep the plug for acceptance and inspection purposes.
2) sound reinforcement system construction often need other construction unit, doing well with other construction units, will have a multiplier effect.
3) devices installed to transfer to the buyer as soon as possible. Upon completion, to apply for acceptance in a timely manner.
4) do the work, the rational use of time, a good grasp of the construction progress, arranged chronologically, to advance work to do ahead of time. Do people, and so on, must not be allowed to work, etc.
5) doing the daily work record and equipment operation records, for the initiative.

【 Weak current College 】 (go) expert detailed professional audio troubleshooting tips 1-Power By 【 China power house network 】

Current professional audio equipment, upgrading is changing, so many devices in use which inevitably there are all sorts of trouble, some are on the device itself, and some of our audio division caused by improper use of the fault of the person, so we talk about the article: "professional sound system troubleshooting methods", I said failure is defined as "soft" fault, is designed for system operation in terms of failures, rarely involve real fault on the device itself, those considered "hard". I have always advocated the "professional", say what power amplifier is broken, Horn bad those are maintenance engineers, our sound engineer's job is to match a good sound system, the various sounds good, doesn't have to be jacks-of-all-trades! lift audio fault is really very painful because various fault really, very difficult in an article that clearly, I can only based on my years with various audio experience to fault of the article written in a simple pop up, I analyzed, generally sound kinds of system failure can be summarized as: total power failure, line failure, human operation breakdown, equipment failure, failure in itself, a total of five interference. The following is an analysis of a serve everyone, and this article explain also explains some troubleshooting audio, so we understand the cases it is even more simple and thorough.

A power failure, sound system

(A), total system power failure: in a previous article I made a sound system overall power profile is important to note the following points: 1, three-phase power: general use professional audio equipment for facilities will apply for the installation of three-phase power supply, the more important place also uses two separate three-phase power supply, just in case one fails so the whole system is down; even very important sites also use similar to PC "UPS" standby power, visible power is so important. 2, audio, lighting and power supply separately: this point in the previous article also told many times, sound system and lights it is best to have its own power, otherwise one is prone to interference, then a work is not secure. 3. total power distribution: light has a strong power is not enough, we must pay attention to the power of distribution: in principle, a mixer and a variety of audio sources equipment to have all the independent power; various peripheral equipment you want to have all the independent power; power amplifier and other equipment you need at least 2-channel independent power supply. Each one independent power supply with the corresponding air switch control, so we're switching equipment is very convenient.

(Ii), the device to a power failure: device itself power failures can also be divided into three parts: 1, device internal circuitry itself fails, the US General audio engineer can't exclude that need professional service personnel or equipment supplier to warranty. 2, power supply equipment, such as some DC-powered device to use a transformer, the transformer will fail sometimes; there is the power cord connected device has a problem, this situation rarely occurs, but also really good power line seems no problem is not powered on, and a power cable fault elimination. 3. patch equipment installations, such as device connected socket, power, timing, etc., the failure rate is very high in relative terms, especially in mobile performance to pay more attention.

(Iii), the power supply voltage, patch equipment failure: now better economic development, energy consumption is increasing, so the power supply voltage is very difficult to guarantee a constant standard, in this case many places using audio to hi-fi system is configured with a regulator, power equipment, but in the selection of devices it is important to note that regulator voltage power and quality; there are places with a power outlet or power source time series for quality rather poor, but also prone to failure. Power system failure case: 1, opened a new ballroom, the days debugging when voltage normal sound system, the system is working properly, but the evening performances, let alone the voltage low to 180 v, also some audio equipment is not working properly. I found this site using a three-phase power, sound system, a phase of lighting system and air conditioning system with a phase, other places a lighting system. When debugging a sound during the day in the ballroom of the lighting and air-conditioning are not open, therefore, power good, night, three-phase power imbalance issues came. Later, the air conditioning system is also a phase alone, the workplace lighting system using civilian electrical system, this three-phase power balance, you have resolved the problem. 2, a dance performance speakers are always issued "lol" the sound of impact, the results I found the quality of voltage regulator is not too good, whenever the regulator regulator pointer runout time speaker on "lol", and then replace the transformer, I found that sometimes there will be a power pulse sound, the results are found when pressing stage camera console, the sound is noise, then put the controller's power simply plug into civil electrical outlet, and ordinary mixer that road total power apart you have resolved the problem. The above example, we know the power failure is caused by a variety of, must rely on our careful installation, configuration and use, so the power part very critical and important.

Second, the sound system line fault

(A), the power line failure: the power of importance have already said, a stereo system using the power of many, there are all kinds of the power cord to connect, for example: sound mixer and sound source Player, and other peripheral equipment power supply, power supply, power supply, power stage, power active speakers, video system, and so forth, a part of the site require a power, so much power connector to secure, as far as possible to avoid malfunction.

(Ii), the signal line fault: If a sound system compared to a single person, then the sound system of signal connector is like a vessel like the "blood circulation", directly affect the stability of the sound system, but even knowing that the signal cable is so important, sometimes fault also occur, together with the following points: 1, signal qualityIssues, this failure is the most chill out, out of this kind of problem we side only innocent curse swear those traders, on the other side would also like to go back line pl., truly depressed. 2. sometimes we spent a good line, pre-installation testing without problems, but after the installation is wrong, this may be installed led signal cable damage, especially some long-distance transmission of wire rod, sometimes during installation when you wear hose too hard pull wire, it may cause damage to the wire; there may be other types of work in construction is accidentally damaged; there may be a wire is our lovely Mickey Mouse and molar power to bite off, anyway the cause of the failure, so off to put some more spare line. 3. signal line welding, welding the signal cable is on the one hand, it is necessary to pay attention to every spot welding quality, previously often see new buildings on the banner: "lasting, quality first" slogan, a hundred years is too long, at least we manufacture of signal lines within a few years to ensure that no fault? there are a variety of signal line is associated with various plug connection between correctly, such as XLR connector card you "1, 2, 3, three contacts, not confused, so the signal line welding fine after multimeter testing, will not be short circuit or open circuit.

(Iii), amplifier and speaker connection line fault: amplifier and speaker connections between the comparison to everyone, will adopt the high quality, thick one speaker cables, speaker cables failed in General is short, now speaker connections are 4-wire Plug and also good point, past many speakers are used, such TS6.35 plug plug shorting of risk will increase; the speaker cable is generally rare circuit breaker, thick line if the circuit breaker in General is artificial, is unlikely to be the issue of wire itself.

Line system failure case: 1, remember 94 years help a dance hall with several boxes 30, when the system sound control room, are all significant LD drive, dozens of boxes will be dozens, dozens of desk drive 14 inch TV doing video monitoring, so that when the tone control room equipment, lines or more, more complex, not like the sound control room, just a few computers. See project is finished, ready to power up the audio control room, I suddenly realized that something was amiss, I asked the electrical light bulb of 100W today so bright? voltage normal? he said no problem, just want to tone control room all device is powered on, I said, and so on, a volume with a multimeter, my day: 380 v! I can't believe the electrician such low-level errors, please let him watch, he just silly, this time the 100W bulb could not withstand high pressure also burned, front just plug in a set of telephone exchange also catches on fire! think really scared me, because the duration is 2 days immediately without sleeping, so an electrician will add the wrong line, but anyway, safety is most important! 2, 2000 friends companies to a customs do function room, where the stage to the tone control room is 80 meters above sea level, 8 on the stage, all only microphone 8 only microphone after opening the noise in the sound like rain is every bit as big as the fundamental acceptance. Then I went to look at all the meetings, decided to put the capacitance microphone TS6.35 Nonequilibrium plug cut off, all for you "by Jack, XLR card all balance transfers. Results 8 to do transmit only microphone, the normal volume, 2 meters away from the speaker basically did not hear the obvious noise, different signal lines, connectors, shaking, therefore we must note that the signal cable caused the failure. 3, 1992, I helped a dance hall adapted a little sound system, a new addition on the stage, the band due to the signal cable is too much I would allow the electrician help tidy up there, he took all the signal lines on the edge of the stage, and then with a large nail to fixed, I'm not good at that time although but didn't say anything, when professional consciousness of course didn't have such a strong now. Is there a mixer after bad, they are using a sound mixer YAMAHA2300 band power amplifier, one channel of the amplifier is broken, fix a day, I went to feel should be the speaker cable, an: really short! then check line, found the speaker cord carpet just from the stage, a few days before the big iron nail just nailed in the middle of the speaker cables, speaker cables at that time also are flat wire, nails through the middle of a short circuit, short circuit parts are made of a line is black and green, more terror, I was thinking: that Japan amp really badly, we put the nails to shaohua! then I cut the cord plugged in again, the boss said that mouse bit, otherwise the electrician ironclad laid-off. The above example, we know how terrible faults, these examples veteran may not be worth a look, but novice is different, and I cite examples of each are the "bloody" facts, I met so many years work, hoping this post will help.

】 【Weak current College (go) expert detailed professional audio troubleshooting tips (3) --- Power By】 【China power house network.

(Iii), the compression: compression is the main feature is, of course, protection equipment, adjust compression below that takes some of the problems and troubleshooting: 1, noise gates THRESHOL: compressor, noise gate does not mean it can get rid of the noise music, it is only useful in systems with no audio signal is in effect, such as: meeting of the leaders in low voices whisper, such unwanted sounds can be used to block the noise gate; but when the leadership of microphone more loudly, noise gate, of course, will not be able to intercept it, otherwise there is no sound out what can do? truth is: when the system useful audio signal burst noise gate threshold level (THRESHOLD), the threshold level has no effect, the system of noise will inclusion in useful audio signals transmitted together, but at that time was the noise of useful audio signal masks, we don't recognize it. Therefore, the noise gate is no way to eliminate the normal audio signal in any noise, it is not like audio workstation in noise sampler that can moderate the Elimination of some of the normal audio noise. Noise gate if adjusted too high music appears "breathing space" phenomenon, it has a no, off, so to avoid this kind of human failure. 2, the compressor's THRESHOLD: compressor section of the THRESHOLD and noise gate THRESHOLD although in part is a kind of threshold circuit, but both function and work status is not the same, two threshold in normal use, the noise gate THRESHOLD may in 99% of time does not work, because most of the audio level signal will be higher than the threshold; and the compressor THRESHOLD may in 70-90% of the time does not work, the opposite is because most of the audio level signal may be lower than the threshold. 3. compression RATIO: adjustment of the compression ratio is determined from the compression is turned into a "comp" or into the "limiter" and its adjustment to combine compressor section of the THRESHOLD, the compression ratio is too low to no effect, too high and sometimes damage the sound quality. Basically less than 1: 6 ratio of compression, the compression feature is greater than 1: 6 compression ratio can be regarded as a limiting functionality. Of course I personally feel that compression ratio adjustment at about 1: 3 is quite appropriate. 4, stereo chain: compression with a stereo chain key (StereoLink), everyone in the adjustment to be careful not to accidentally press this key, as will the stereo signal into Mono signals. 5. express Bypass: I often find that some audio Division has the express compression is still unknown, can't tell what is express state what is working, therefore this point to note. Compressor failure examples: 1, a time-based maintenance to a set of audio equipment, found a bench press machine is not too normal, compact led light 3, 4, and the other side of the compact led should light up 7, 8, but in front of the compression for all devices are working properly, can only be a compressor for itself. Later discovered that the compression is on the back panel has the side-switch on-20, normally to select + 4dB level worked, and other device-level mismatch, compressor for signal easily severely distorted. We use the time do pay attention to avoid this kind of failure. 2. once my friend to me said he was there to audio equipment problems, when you play songs in concert accompanying music system also everything is normal, but when the singers sing loudly suddenly started, the system overall volume will suddenly have a lot of small, like a breath to, and having a tough time and slowly return to normal, I find that they are using compressor dbx 266 of the United States, said phenomenon is the compression of the threshold (THRESHOLD) the threshold level is too low, the compression is overworked. This time the need to raise the THRESHOLD level, this failure is ruled out. This phenomenon is the dbx 266 compressor for a characteristic, therefore we should note that in the future. 3. once I find a lethargic friends to help a dance tune, said that under the sound has just opened, evening dance 8 only secondary speaker speakers burnt on the whole, I find it very strange, except where the sound engineer a serious operation, accidents will happen this kind of "disaster" of consequences. After careful and comprehensive examination I found audio system compressor for only resizing properly, causing such serious consequences. Originally this audio system only in main speaker before configuring a compressor, there is no auxiliary speaker. I found that one compressor for threshold (THRESHOLD) level adjusted too low, at around and 30dB-compression ratio is also adjusted in 6: 1 cent, so that even a normal audio signal had also been a lot of compression, we all know the standard signal level is 0dB, you can imagine, such adjustment, whether the compression is mentioned in the input signal, compression for normal output signal in any case or is not up to standard 0dB level, its consequences are: that night sound engineer always said no sound from the main speaker, ran in a mixer to increase the volume, so that the signal serious distortion, on-site or just hear the voice of the auxiliary speaker, as the main speaker to compressor for thorough "killed", of course, the sound will be very small. This poor little 8 auxiliary speaker speakers to burn it into pieces, and 16 main speaker only significantly but unknown lay to rest. Lessons are painful, but it also from the side shows the importance of the press, we first highlighted THRESHOLD-threshold level and compression ratio, the RATIO is the hope that we can thoroughly understand these principles and features of the knob, adjust the improperly, it can produce catastrophic failure. 4. we all know that some of the mixer will have a mono output of the total volume, there are times I had a project, from the mixer mono output signal to a compressor, the compressor in stereo chain key (StereoLink) open, and then the signal output to a secondary speaker amplifier, a few days there stereo masters say half the auxiliary speaker no soundI checked and found to press the stereo chain key (StereoLink) does not open, it becomes to press for the left channel signal, right channel no signal because there is no "chain". Through the introduction and examples we should know that the compressor is a very important essential equipment, this need we pay close attention, in particular the project developers, sometimes with single time could spend more money with one compressor, final result is often a stingy, may damage outweigh many shouldn't have damaged device!

Weak current College】 【daily tips on how to use the projector carrying case --- Power By】 【China power house network.

Projector carrying case can be said that the projector is inseparable from daily use part of mobile projector when carrying case became a faithful partner of projector, portable bag not only to provide portable projector while the projector in the move process provides earthquake, ruggedized, etc, but often a lot of users will ignore the role of the carrying case, which is not a good many projectors play a protective role. For example we have seen users of NEC VT47 projector feet knock off, in fact simply because the user itself didn't notice good projector carrying case for use and, in the following we will explain through actual legend to change with the correct use of the package and its role.

First, open the projector package, drawings in the carrying bag for BenQ projectors backpack, the wall can be seen carrying case with foam cushioning layer, this is to raise the projector to bring shock in the process, such as BenQ carrying bag is directly change stitching backpack around, and some carrying case is designed with tank type, you can directly check out into the projector into carrying case.

2. when placed into the projector, you also need to put the projector fixed belt buckle, and at the same time projection lens cap must also be installed, and note that the projector's lens should be like, and must not go down vertically, so that the carriage process is very easy to knock out the lens while the projector needs attention expansion bracket fully retracted fuselage, so clean to avoid moving to head off in brackets, such as NEC and Panasonic models which support most of the design on the sides, and both are made from plastics design, very easy to move the process inadvertently knocked off, many users didn't notice directly to the camera to display the results of many of them are the bracket to knock off.

Third, the length of the shoulder belt carrying case need to be adjusted to the best, bearing in mind the skid blocks and shoulders close, you can increase the friction to prevent falls. At the same time can also reduce the pressure.

4. at the same time you need to check the shoulder straps and backpack of key buckle is close, there is no loss of

5. If you want the projector mount portable package send, please be sure to place it inside the box of the cushion enough cushioning material to prevent damage to the projector mount portable package as a package send may damage the worst projector. Also note that the projector is placed into the carrying case is the need to ensure that the projector is cooling completed!

Weak current College】 【professional audio engineering sound field design steps and features.

<br> A professional audio works of important work is the sound field design, works for the ultimate quality, sound field design is also a key point. The purpose of sound field design lies: the use of scientific computing do guidance, for audio equipment .to build an ideal sound space, the device performance fully. In a small number of strict construction decoration and design, generally to make the necessary sound field design, but in order to standardize and follow the steps for professional audio engineering work, eliminate any irrational .factors, for the following other design guidance, it is necessary to carry out the design of the sound field. <br> <br> Sound processing - this is the sound field design is the first step, but also many technicians easy to ignore .the steps. The purpose of sound insulation is in a specific area within the creation of a project are not subject to external influence or impact on the outside of the quiet sound field. It includes external sound reinforcement of sound insulation, sound insulation between rooms, .soundproof walls, are part of the Windows and doors and ceiling. First of all to look at and outside noise, this task is not to let outside noise incoming indoor or indoor voice to the outside. This work, it is necessary for building design and .construction units to the architectural structure of the consultation of sound insulation, further you can learn more about the environmental sector. The concrete implementation, outside noise transmission such as indoor Interior you can to control the total noise is usually higher for practical sound engineering requirements in .the following 35-40dB; indoor voice to the outside world can look on the outside of the environmental impact, in accordance with the provisions of the environmental sector, generally not higher than the average 10-15dB for good. <br> <br> .Practical engineering needs to address parts of the walls, doors and Windows and is ceiling several places. Usually the Auditorium and the outside of the wall most can meet general sound engineering, but if the sound system of the sound pressure level is relatively large, working .time more at night, you should let the construction sector to consider increasing the thickness of the walls; Windows and doors is an important part of sound insulation, often a small window to improper handling, resulting in the sound insulation failed, general attention to: .1. try not to let the door gap, experiencing frequent switching and indoor and outdoor sound are relatively large, you might consider setting the sound isolation channel structure, this is it. 2. to increase the window structure and material thickness, if necessary, .you can use leather door and double-glazed Windows. 3. If the sound effects need better hang on doors and Windows, in the heavy curtains and shutters are more economically viable way. The sound insulation of the ceiling is also not be neglected, especially .the roof is not a concrete structure, instead of using scaffolding structure, the ceiling of acoustic leak is more serious, you need to install the ceiling of the material and the quality is high, if you need to take into account the increase in the ceiling .barrier or the ceiling laying versamat approach to meet the requirements of sound insulation. <br> <br> Second is the sound insulation between rooms, its task is to make room in the audio system when mutual interference to a minimum. Although the various standards .and regulations on this index is not required, but the quality of the audio engineering has a significant effect. Practical engineering needs to handle parts or walls, doors and Windows and ceiling, but processing requirements different from before. General indoor certain thickness of the concrete .or brick wall acoustic requirements or to be able to meet, it's important to note that some of the extra room dividers, they usually use a simple light steel keel fill a certain amount of fire-absorbing asbestos method, this is for the sound engineering is .absolutely not enough, this is the case, you need sound designers to make architectural decoration units, for example, the solution can be used following this increase casing solutions. But for high power bass of isolation is not used to resolve the thick brick wall; .sound insulation of doors and Windows are not ignored, particularly pay attention to the quality of the production of doors and Windows, because a lot of sound interference are derived from the poor quality of doors and Windows of the slit, of course, necessary, or .you can consider using hanging curtains and shutters approach to sound; sound insulation of the ceiling in the room sound insulation between rooms, but more importantly, we can look at this common casino room layout diagram, you can find the Hall ceiling above space is at .the top of the surrounding box is connected, so that in the Hall for entertainment or performance, we have an impact on the balcony, it must be sound on the ceiling. <br> <br> Generally speaking we can lobby ceiling and balcony at .the top of the add another layer of sound-absorbing panels for insulating layers, or in the ceiling on coverage of certain thickness of fire protection sound absorbing mineral wool for sound insulation. On-site noise reduced - in most practical professional audio engineering, .air conditioning and ventilation, are some of the equipment to be installed, these devices work noise will to a certain extent affect the quality of the sound field, so there should be at design time for a solution. Air conditioning and ventilation equipment is the best .choice for low noise, stable product, as far as possible, so that when you install air conditioning compressor away from doors and Windows, fan power a loud noise is difficult to control, you can use the fan installed in the duct inner structure, as .shown in the following figure. <br> <br> Implementation of a sound field uniformity - sound field uniformity of requirements throughout the public areas, the average sound pressure value deviation to a small extent, General requirements in the following 10-12dB, .otherwise it will cause uneven sound field, reflected on the local sound pressure, some local and small, to feel very bad. In a real project in architectural structure and sound system layout for acoustic field uniformity. In building structures, should be avoided as far .as sound reinforcement area larger column, avoid large concave-shaped structure, building decoration, to try to make the entire range of decorative structure and basic materials, particularly given the limited funds, walls with cement la hair structure is a good way to achieve sound .field uniformity, of course, if you would like a decorative design as computed by the concert for a variety of different diffuser, save money and be able to achieve very good results; the layout of the audio system can be largely solved sound field uneven, .in General, long narrow Hall sound reinforcement must sound reinforcement area to expand along the long side, as shown in the following figure, space higher sound reinforcement occasions to try to toneBox location elevation, preferably slightly tilted backward field, as shown in the figure below ., if you are in space and space is a large place for sound reinforcement, they should consider speaker set arc formation hoisted into uniform sound diffusion. Visible sound system layout can solve sound field does not have the problem, if strict sound field, you can .also use sound box manufacturers to provide sound field design software for simulation and remediation, of course, the best approach or in the construction of architectural decoration design as far as possible, so that when the sound field with uniform. <br> <br> .Sound field flaw avoid - in many audio engineering have varying degrees of sound field flaw, audio highlights, audio chatter, audio feedback, voice resonance, these issues are brought to the acoustic field flaw, and these defects caused by problems in the practical use .is very difficult to resolve. For example, the acoustic field feedback and resonance occurs on the system does not work. Effectively address them, the best time is in the design and construction of architectural decoration. Usually we can consider the following aspects, 1. .try not to sound reinforcement locale large glossy concave structure, including the roof and walls, particularly on the stage to taboo, if compelled, in front of the concave side hung heavy cord or placed objects, this sound is not likely to occur in focus, .2. try not to sound pressure larger area set two parallel reflection strong walls, especially when the sound reinforcement area Strip also to note that this can effectively avoid shaking the fibrillation, 3. General comparison as long as the sound field, there is no sound .focused evenly, not sound reinforcement-gain sound feedback when you are not likely to occur, we can also take advantage of the system layout and Equalizer Spectrum Analyzer to correct, so that actual use is even not happen acoustic feedback, 4. voices of resonance .and decoration material and construction are closely related, it is important to avoid sound reinforcement locale larger cavity volume, certain requirements for special decoration technology of reasonable, don't let loose material connection, such as: gypsum ceiling if not pad is installed in the .aluminum frame, a major public address sound pressure, prone to resonance, particularly the low-frequency signal resonant certainly occurs frequently. <br> <br> Calculation of the reverberation time - on sound field of all specifications, the most familiar is the .reverberation time, it is also easier to control in the design of the measurements. If the design of control correctly, a sound field effect performance is outstanding, the sound will be mellow, full, not excessively bureaucratic, not dry. Reverberation time control of .the key is: use the appropriate calculation, guiding the setting of decorative structure and material selection, so you can reach the reverberation time target value. For different types of sound engineering, reverberation time requirements vary with the type of project, different sound field size ., the reverberation time indicators differ in design we can refer to the chart below to determine the value of the reverberation time, it is based on project type and the size of the volume of sound reinforcement area to the given the reverberation time, close to the .recommended value range, sound field will achieve better results. Here also should be noted that: there is now a lot of designers will set the value of the reverberation time is smaller, then use the device in the reverb to increase sound reverberation time, doing .so not only does produce youmei natural reverberation effect, and to some extent undermined the original recording signals in a direct-to-acoustic signal is not desirable. <br> <br> General engineering calculation formulas are used in the following two formulas below is .the contents of a various parameters, in general we can 500Hz and two local computing 1000Hz acoustic reverberation time. We evaluated all the on-site materials broadly identified and statistics better their respective area, from the construction manuals or product brochures, respectively, to access .their 500Hz and sound absorption coefficient of 1000Hz, you can calculate the average of the acoustic field sound absorption coefficient, area, volume, sound energy coefficient and the average absorption coefficient calculation takes the field at the time of 1000Hz 500Hz and reverberation time, if the .calculation results and recommended reverberation time values are relatively large gap, and decorative units to reduce or replace a consultation with some materials, and then evaluated until satisfactory, in calculations must be building materials of the area and the sound absorption coefficient statistics correctly, especially some .perforated acoustic Board, perforation rate disparities of different sound absorption coefficient, to influence the final result is also larger. In addition, performed works, the calculation of the reverberation time also the empty field, and the audience applause of all time. Sound pressure level .calculated - sound pressure level is a professional audio system, an important indicator, a reasonable scientific sound pressure level of the sound field effect, equipment selection, actual operations have a significant role, but also for making good listening environment created good conditions. < .br> <br> The sound pressure level calculated before, also have to determine an appropriate environment suitable reference sound pressure level, and the reference sound pressure level and the project type also has a close contact. Determine baseline sound pressure level, but also look .at the normal human auditory sense curve, we can find in different frequency, people on the same sound pressure level of perception of sound is not the same, this perception in professionally known as loudness, unit is Phono, with this measure of value, we .can according to actual project type, according to their frequency of sound reinforcement signal characteristics, you can determine a suitable reference sound pressure level. Usually for music playback-based system, take the 85-90dB, for consisting mainly of sound reinforcement system can take .70-80dB, plus 12-18dB peak levels, plus 1-3dB of environmental noise margin, you can get an average rating of listening location sound pressure level. The sound pressure level is the system you want to average listening distance needed to achieve the .sound pressure level, then the sound pressure level and how to convert to the device itself rated sound pressure? this requires a sound propagation of sound pressure level change map, we can see, we require that the average distance from the listening of sound pressure level .in this position, but the device itself rated sound pressure level is here, when you need to calculate a formula for this kind of sound pressure level, so that finally the sound pressure level calculated isSpeakers at its premises need reach 1m sound pressure level, it .is followed by electrical calculations and equipment selection basis. <br> <br> Through sound field design we can find: professional audio engineering of the sound field design content more results on project quality, equipment selection and system of work is very important. Specific .needs in the design, construction and decoration elements involved or more, some still in close contact, visible sound engineering in the design of the start of construction or decoration unit needs to be closely coordinated with, so we need to get help as soon as possible ., as soon as possible in the design, so as to achieve better results. <br> <br> <br> <br> <br> <br> <br>.

Weak current College】 【audio glossary.

GAIN: input signal gain control
HIGH: treble level control
MID-HIGH: treble level control
LOW: bass level control
PAN: phase control
MON.SEND: tap listens to signal control
EFX.SEND: tap effect signal control
LIMIT (LED): signal amplitude indicator
LEFT-sided signal level control:
RIGHT: the right road signal level control
MONITOR: monitor system
MON.OUT: monitor output
MASTER: General road level control
EFX.MASTER: effect of the output level control
EFX.PAN: effect of phase control
EFX.RET: effect return level control
EFX.MON: effect send level control monitoring system
DISPLAY: level meters
ECHO: reverb
HIGHIIN: high-impedance input
LOWIIN: low resistance input
OUT/IN: output/input jack
AUX.IN: auxiliary input
MASTEROUT: total output
EFX.OUT: effect of output
EFX.RETURN: return enter effect
LAMP: special lighting power supply
POWER: total power switch
BALANCEOUTPUT: balanced output
FUSE: a fuse
PEL: pre-listening (audition) press
EFF: effect of level control
LEVEL: channel balance control
HEADPHONE: Headphone Jack
PHANTOMPOWER: phantom power switch
SIGNALPROCESSOR: signal processor
EQUALIZER: equalizer
SUM: total output group switch
LOWCUT: low frequency cut switch
HIGHCUT: high frequency switch removal
PHONOINPUT: phonograph input
STEREOOUT: stereo output
ACTIVITY: dynamic indicator
CUE: selected to switch
MONOOUT: mono output
PROGRAMBALANCE: primary output sound image control
MONITORBALANCE: listen to output sound image control
EQIN (OUT): Equalizer access/exit key
FTSW: foot switch
REV.CONTOUR: reverb profile regulates
PAD: fixed value decay, attenuator

【 Weak current College 】 cinema-the right choice of projector screen

Install the appropriate type of screen to film shows significant impact experienced and for cinema operators to save money.

Screen for film shows experience produces several implications-the most important thing is the quality of the movie screen: brightness, contrast and color reduction and potential defects of the silver screen distracted. Screen the screen rear speaker system for acoustic performance, especially high-frequency loss affect the brightness level of screen to ideally through references worldwide accepted standard SMPTE. The standard provides that, when viewed from a central location, the altar brightness to achieve 16-foot Lambert (55 candles per square centimeter) square minimum brightness of screen 12-foot Lambert.

The audience can see the screen brightness depends on several factors: show lamp light lights from the mirror, show through the lens and show the window to the screen between optical loss and reflection from the screen to light. Modern cinema projectors use Xenon lamp (relative to the legacy of carbon lamp technology) has a different power, according to screen size of different sizes, the most number of multiplex 2.0 Xenon lamp power kW to 7.0 kW, higher light output light power, but the higher the cost of the Xenon lamp power.

The screen is the optical brightness reflected back to the audience. White plastic curtain makes light scattering, and most of the light reflection to the ceiling and the side wall was lost. Referred to as the "gain" screen will be more light directly back to the audience. Screen gain level and the amount of light reflected back, its measurement in accordance with the reference standards (with light reflectance value 1 carbonation magnesium Board). Commercial white plastic curtain of reflectivity varied, but generally have under reference standard 0.8-1.0 reflectivity. "Gain" screen can have 2 or more gain levels, but for the theater's screen is the size of the screen under yingting usually best 1.4-1.8. More than 11 metres wide screen with a gain of the screen will normally have receipts screen width exceeding 14 m when it is better to use high-gain (1.8) screen. Gain more than 1.8 high gain screen produces "hotspots" (that is, the screen Center looks too bright).

Now some theater are using digital show as a 35 mm slide show options. Latest digital projector can output up to 17000 lumens of brightness. The figures show the light output is likely to reach traditional projector brightness, so the screen width is greater than 10 meters with an income gain of the screen.

White plastic curtain is usually installed on the flat screen so that however of light reflection and yingting parts the best viewing angle, gain screen the best installation in curved screen. Because of the white plastic curtain makes light scattering, if using curved curtain frame will have a contrast ratio of losses is therefore not recommended. Gain screen of ARC ARC depends on many factors, but usually 20: 1 ratio of chord height.

Weak current College】 【acoustic impedance-in - Power By】 【China power house network.

<br> Impedance is the audio ring most frequently seen in words, but it is intended that he means? many people see loudspeaker impedance values are shown for four or eight-ohm, will intuitively picked up three use the meter to the Horn of a .second terminal, take a look at the end is not correct, unfortunately most people are disappointed, because three use meter amount of electric resistance stalls the result did not and speaker mark above. Reasons? because you're mistaken, you are wrong. Impedance .and resistance is not completely consistent East. In the State of physics textbooks, our first contact with the electrical theory, which refers to the voltage, current, resistance and power between theory and mathematical relationships. The vast majority not to pursue a course of electrical .or electronic profession, his lifelong dedication to do electrical knowledge is concerned, this is when the class didn't sleep, after efforts, serious and hard to have brilliant results, no wonder you will put the impedance as resistance. Impedance literally and resistance, .of which only a stop word is the same, and another against Word? simply put, the impedance is resistance combined with reactor, so we called impedance; distribution point, the impedance is resistance, capacitance and inductance of resistance in the vector and. In .DC world, objects on the current role of the obstacle is called resistance, all substances have resistance, resistance values of size differences. A substance called resistance conductor resistance and great substance called a non-conductor, and recently in the high tech field called superconductors ., is a kind of resistance values to zero. But AC field in addition to resistance prevents current, capacitance and inductance also impede the flow of electric current, this role is called reactor, meaning the resistance current role. Capacitance and inductance capacitor reactance respectively called .on short resistance, inductance and capacitance and inductance. Their measurement units is the same as with the resistance, ohm whose value is the size and frequency of the alternating current, frequency, the higher the capacity less resistance gankang, the greater the frequency, the .lower the capacitance, the greater the feeling less resistance. In addition capacitor resistance and inductance of the phase angle is also issues, with the vector of relation, will say: impedance is the resistance and inductance of the vector. General audio equipment commonly cited impedance .of loudspeaker impedance, pre-amp expanding machine input impedance, fore output impedance, (after the class is typically not called output impedance, and that output resistance), signal wire transfer impedance (or characteristic impedance), etc. If the equipment's internal electronic .circuit and part of the various parts of the impedance that many more superb complex, non-few words can explain it clearly. Here we post only briefly describes the impedance of the audio equipment marked with what kind of real meaning. Due to the impedance of .the units still ohm, Ohm's law also applies, in short, in the same voltage, the higher will flow through the impedance less current, the lower the impedance will flow through the more current. Light is as simple as a sentence, do you know .how many audio equipment matching learning in which? from the loudspeaker impedance. The most common to the loudspeaker impedance 8 ohm value is shown, there are also many is 4 ohms, this represents the? this represents the trumpet in a factory test rules, when .the input signal by a sine wave 1KHz, it renders the impedance value is 4 or 8 ohm; or is in the Horn of frequency response range, an average of impedance value. It is not a fixed value, but rather as the frequency of, .and may even be rolling scary and may to a certain frequency to 10 20 few Ohms or lower a frequency to a Ohms or less (this Horn is generally regarded as the killer after level, to the most famous Apogee). Well, let's brainstorm about .; when a fixed after level output voltage to the trumpet, according to Ohm's law, 4 ohm speakers than the eight-ohm speakers more electricity flowing through a times, so if you are computing power, and you'll understand why the market will be .rumors a eight-ohm output 100 Watt Crystal after the class, in four-ohm speakers connected automatically to 200 watts. But you don't, that was cheap, Grand don't come for free, when the speaker impedance value all the way .down, after a fixed voltage level output, it will flow through the current increasing, you determine your level can output after so much current? you know all the way down the loudspeaker impedance to the later on the results a bit like a loudspeaker cable directly .short-circuiting of meaning, and thus lower impedance values sometimes low-ohm speakers called Apogee after the class killer, you understand! all Crystal after the class extending machine, its output current capability has its design constraints, outside this range, the machine will .be burned. This is why most people often say: after the level of power is not big, but the output current to big it is were it not for the reason (this issue we will discuss in detail later). Similarly, if a speaker .impedance is high, like the early 15 RogersLS 3/5A, then expand the machine output power would not automatically by half? Yes! if the efficiency of the Horn is low, you should send it to the treble pressure, can not use extended machine .with high power? and Lakes there are rumors: rise of the records in the North Zhongshan Road, Taipei City Centre has a pair of Rogers 15 LS 3/5A, used as background music. Push its expanding machine is a Japan early comprehensive expansion machine .Technics, but including Liu, Lai editor-in-Chief, managing directors and are highly praised it well, you say? early Japan to expand the machine gave the impression that is power indication is very high, but the output current capability of the quite .diplomats, don't you see the small set of bedside stereo mix still is 300W? but KRELL's after the class you want to 300W a person is carrying and carried. This high-voltage and low current in Japan to expand the machine a meet now .styling are all low-impedance speaker, soft foot at once, but if you run into a high-impedance speakers, for example ... Will it become a veritable when Harry met Sally? collocation of! how can sit idly by..

College】 【weak flat-panel TV to buy depends on "physical resolution" --- Power By 【China】 weak home network.

<br> Following the 2004 DLP and LCD projectors after World War II, 05 flat panel TV LCD TV and plasma TV phone-in was underway, especially from the "May Day" golden week to now, manufacturers launched models of flat-panel TV brand .range, so that consumers get confused and disoriented. .Author based on many years of work experience and practice, LCD TV and plasma TV in the performance comparison, combined display can receive digital TV will begin broadcasting high-definition TV programs and other issues talk about some of the views for the consumers. .<BR> <BR> "Physical resolution," Identification of high-definition <BR> <BR> digital television (including satellite digital television broadcasting, cable digital television transmission, terrestrial digital TV broadcasting) in 2005 and 2007 have been launched, consumer .who can show HD programming to choose the image LCD TV or PDP TV. .So, how to identify market sales of LCD TV and PDP TV is HDTV? .<BR> <BR> LCD TV and PDP TV are fixed resolution TV, has a physical resolution (ie pixels) of the points, screen size, pixel count is to determine whether the image shows an important basis for high-definition (of course, and circuit .related). .<BR> <BR> 42-inch PDP TV market, most of the physical resolution is 852 × 480 or 1024 × 768, if the display high-definition image resolution is 1920 × 1080, Amplitude ratio of 16:9, the image is displayed .HDTV resolution difficult to achieve the requirements, that is, the horizontal and vertical resolution of 720 TV lines or more. .However, high-definition images can be supported or compatible, and manufacturers and merchants to call this 42-inch HD PDP TV machine. .<BR> <BR> More than 50 inches for PDP TV, mostly the physical resolution of 1366 × 768, a few have 1920 × 1082, can display high definition images, but 1280 × 720 of the PDP TV, if the circuit transformation, motivation circuit .better high-definition images can also be displayed. .Recommend that consumers choose to buy PDP TV screen 50 inches or more, the physical resolution of 1366 × 768 or more in, but the price to be expensive. .Large price cut 42-inch television, most did not give instructions on the physical resolution, but also can display the individual is given in standard definition image resolution of 852 × 768 physics. .<BR> <BR> LCD TV screen size from ten inches to 65 inches there. .20-inch LCD television is generally following an early production line, the technology is relatively backward, response time, the physical resolution, viewing angle, contrast, brightness, and other poor performance, for the PC to display the teletext screen, the image does not display video .ideal, although the price down so low, in the purchase to be carefully considered. .The 25-inch to 30 inch LCD TV, general physical resolution is 1024 × 768 or 1280 × 720, can support high-definition image display, image resolution better than small-screen LCD TV, but sports a larger image trailing; for 32-inch .-37 inch LCD TV, most of the physical resolution is 1366 × 768, can display high definition images, but a few 37-inch LCD TV, the physical resolution of 1920 × 1082, horizontal and vertical resolution up to 1080 TV lines. .For more than 40-inch LCD TV, basically 1920 × 1082, but the price is expensive, so that consumers stay away. .LCD TV high-definition still images, but there is motion smearing the image, when viewing moving images through the brightness level of sense and as PDP TV. .<BR> <BR> Also depends on the TV interface, the general must have the Y, PB, PR input interface and DVI (digital video input interface) port, preferably also has HDMI (High Definition Multimedia Interface, than the Y, PB, .PR and DVI interfaces are more powerful) and digital audio and video interface. .Should be noted that, although some domestic brand TV with DVI or HDMI interface, but its poor performance, in the performance of foreign brands than domestic brands. .<BR> <BR> Election on demand <BR> <BR> LCD flat-panel TV and PDP TV sets have advantages and disadvantages, choose what kind of television, according to consumer demand. .<BR> <BR> Do not care about the money for the consumer, the manufacturers of top-level products can anything and everything, choose LCP TV and PDP TV are not the point. .But the purchase of 50 inches above the TV, could focus on the PDP TV. .For the salaried class, purchasing products, according to demand. .If you buy 42-inch LCD TVs under the proposed 32-inch -39 inch choose if to buy 25-inch to 30 inches, will have to consider the physical number of pixels can display high-definition images. .<BR> <BR> If the room is large, complex lighting conditions, choose the 50-inch PDP TV is better than the 50-inch LCD TV, now are cheaper in price. .If only in the bedroom, usually look at news or drama, consider 25-inch LCD TV around. .In short, for the majority of consumers, according to their needs and financial situation, after the actual inspection, or to the relevant expert advice, you will be able to buy a flat-panel TVs satisfied. .<BR> <BR> Links <BR> <BR> LCD TV and PDP TV advantages and disadvantages compared <BR> <BR> LCD TV advantages: <BR> <BR> 1.LCD TV, PDP TV screen size for more than like .of, from a few inches to 65 inches (currently do) have. .<BR> <BR> 2. Physical resolution has to do 1920 × 1080, the horizontal and vertical still images up to 1080 TV lines resolution, image detail, clarity. .<BR> <BR> 3. The image of high brightness, better than the CRT TV and PDP TV. .<BR> <BR> 4. The image is almost no distortion, because the screen size of diverse applications in the computer better than the CRT and PDP. .<BR> <BR> 5. Can be flat, thin, light volume, low power consumption. .<BR> <BR> 6. Afterimage image smaller. .<BR> <BR> 7. No radiated interference, image flicker-free, long-term viewing without eye fatigue better than the CRT TV. .<BR> <BR> LCD TV disadvantages: <BR> <BR> 1. Small viewing angle, brightness, contrast and saturation decreases with increasing angle, chroma error increases as the angle increases, .the image quality decreases. .<BR> <BR> 2. In all displays, the slowest response time, so watch the moving images, especially fast moving images, the resolution dropped. .<BR> <BR> 3. Contrast, on-off ratio (full white / full black contrast) worse than the PDP TV. .<BR> <BR> 4. Due to use of backlight, easy to produce light leakage, full-screen brightness uniformity is poor, worse than the PDP TV. .<BR> <BR> 5. For a fixed resolution of the imaging device, when the image signal format and display the same time, the need for format conversion, bringing the image quality decreases. .<BR> <BR> 6. On the big screen size, though better than the CRT TV, but inferior to the PDP TV, when the size is larger, higher prices. .Currently on the market 32-inch 42-inch LCD TV and PDP TV prices almost the same. .<BR> <BR> 7. There is no high-quality flat speaker support. .<BR> <BR> PDP TV advantages: <BR> <BR> 1. In the direct-view flat panel TV, the screen size can do the most, now be 100 inches, which is a CRT TV, LCD TV unparalleled .The. .<BR> <BR> 2. Image clarity, color reproduction is good, bright colors, high contrast, on-off ratio (full white / full black contrast) high, in the dark field, the image-level good. .<BR> <BR> 3. With flat panel TV's most wide angle and very dark black. .<BR> <BR> 4. Short response time, moving images better than LCD TVs trailing. .<BR> <BR> 5. Full-screen brightness uniformity is good, better than the LCD TV. .<BR> <BR> 6. With the maximum, the thinnest flat-panel displays, small size. .<BR> <BR> 7. Image without blinking, the eyes do not fatigue long-term view, better than the CRT TV. .<BR> <BR> PDP TV disadvantages: <BR> <BR> 1. Maximum peak brightness and dynamic range of the average image brightness changes with the change. .<BR> <BR> 2. Because there was space between pixels, resulting in pixels of the image to see more clearly at close range. .<BR> <BR> 3. When the signal format and display the image at the same time, the need for format conversion, image quality decreases. .<BR> <BR> 4. Size should not be less inconvenient for computer applications, flexibility on the inferior LCD. .<BR> <BR> 5. Useful to the average maximum peak brightness and low brightness. .If the images at high brightness, high power consumption, lower life expectancy. .<BR> <BR> 6. At 50 inches, the number of pixels is not easy to do high-definition display images is poor, worse than LCD. .<BR> <BR> 7. In high pressure, high current, a larger number of assembly parts, and more for the high-voltage components and electromagnetic interferences. .<BR> <BR> 8. Afterimage larger image, is inferior to LCD TV and CRT TV. .<BR> <BR> 9. Because of small size, there is no support for high-quality flat speaker, the sound fidelity is poor. .<BR>.

【 Weak current College 】 line pass campus intelligent broadcasting introduction---Power By 【 China power house network 】

System features:
1, single-cable transmission: leverage existing a CCTV cable (75-5, 7), the realization of all signal transmission and automatic management control. Frequency range 108-140MHz;
2. any partition: unique arbitrary partition function, you can implement multiple different grades and different classes independent control and any combination.
3, points independently addressable: enables point-to-point control, control of arbitrary grade or arbitrary class speaker channels and switch or full on full off.
4, regular broadcast: users can prepare various channels for a week of scheduled playback program, to play the content, the broadcast time, play area, and so on, can be arbitrary programming control.
5, AutoPlay: computer according to the program automatically scheduled playback, unattended, play before the system automatically opens the appropriate region points to the power of FM sound, play is completed delay closes automatically.
6, long-distance remote control: via wireless remote control system for outdoor long distance remote control host playlist.
7, long-distance speech delivered by wireless mouthpiece enables outdoor distances. Combining both line remote control system is very convenient to use.
8, free spots: during playback, the user can at any time to stop a scheduled play, random insertion of other programmes, spots is finished, the system continues to follow the program to continue playback.
9, beautiful sound quality: FM audio range 30HZ-15KHZ, distortion, General 0.7%; whereas the constant pressure broadcasting system audio range 200HZ-12KHZ, 10% distortion.
10, remote speaker: Terminal classroom can remote control to choose playback channel.
11, local PA: speaker with audio input interface, solve the classroom local programming not broadcast source volume.
12, supports a variety of popular audio formats: mp3, mpg, dat, avi, mid, wav, etc, you can record and play a variety of external media source (e.g. CD, VCD, decks, radio, microphone, etc.).
13, the operation is simple: Studio software is powerful, interface humanized design, easy to learn.
14, rejection capability: FM radio to FM (108-140MHz), less susceptible to outside influence, and FM radio itself features a computer lock-compression technology, you can filter out interference.
15, powerful channel management: user may act according to the actual program is now more while playing 1-12. Any extension.
16. system capacity infinite: receiving device is not affected by the number of restrictions that can be increasing.
17, control management: System can control center-control management, teacher play their own program content can do not need to center the engine room, making use of the Campus LAN PC + minute control host and can be any point to play management, greatly facilitates the process of preparing for the teacher.
18, emergency plans: unique emergency broadcast packet partition, mandatory broadcast feature in the off state of the computer system for broadcasting, has just had a computer crash emergency plans.
19, power management: unique power centralized management capabilities, you can set auto power off all classroom speakers can also be distributed automatically closed floor speaker power, highly intelligent design.
20, lighting management: you can use this system to implement automatic management of campus lighting needs to realize time switch campus lighting.
21, fire broadcasting: the use of this system of fire management machine to fire alarm signal and broadcast system linkage, and have priority;

【 Weak current College 】 electronic ballasts in stage computer application of lighting

With the extension of the green lighting, a.c. supplied electronic ballasts for start, entered the 1990s, various gas discharge lamp with electronic ballast and a variety of new electric light source in the world are emerging, formation called the "green lighting" of new industries. Gas discharge lamp as the main stage computer lamp light source, configure Exchange electronic ballast is a general trend.
Conventional inductive ballasts in use has significant drawbacks. When the AC over zero, lamp will result in the fire, which will make the lamp flashes of light produced 100Hz, thereby reducing the lamp's luminous efficiency. At the same time, the inductive ballasts to avoid core vibration to be populated with asphalt, results at run time to produce audio "humming" sound. In addition, inductive ballasts heavy, usually a 1200W of inductive ballast weights 13Kg; and inductive ballast loss, fever, severe; voltage fluctuations, the lamp current fluctuations as well, when the power supply voltage is increased by 10%, the lamp current increased 17 per cent, which greatly improves the lamps and the life of the lamp.
Electronic ballast and traditional inductive ballasts compared to commonly used, have many advantages, such as increased lamp and circuit efficiency, energy saving, easy-to-achieve dimming control, no stroboscopic, non inductive ballasts unique "humming" sound, etc. Inductive ballasts faults in electronic ballasts in most of them can be overcome. Electronic ballast is actually a high frequency of self-excited Oscillation (he dared) converters, electric discharge lamp is a converter of load, load circuits are often set up a series resonant circuit.
The advantages of electronic ballasts are reflected in the following areas:
1, high-frequency self-excited Oscillation (he dared) converter and the series resonance, its load can apply various gas discharge lamps simply change the resonance circuit capacitance, inductance parameters to select suitable Q value, can drive various specifications of the gas discharge lamp load, Kai-voltage lower fluorescent lamps, or restart-voltage high pressure sodium lamp, metal halide lamps, etc.
2, the series resonance load circuit voltage supplied to the fluorescent tube is high frequency sine wave, sine wave voltage driving lamp makes electrode loss and high frequency arc stability; and relative frequency will increase 15% light emitting efficiency.
3, high-frequency converter and the series resonance inductance combination, for discharge lamp equivalent from a low impedance voltage source into a high-impedance current source for choke and constant power supply.
4, in the high-frequency converter power grid side access power factor correction (active or passive), the power grid side power factor improvement to 0.95 above, even up to 0.99.
5. lamp used in the process of aging, aging will gradually be given electrode activity element of emission performance continues to decay, the ageing lamp luminous flux is also declining. However, the electronic ballast of resonant circuits can consistently providing compensation to the lamp, the lamp maintain electric energy efficient lighting, lamp service life is extended.
6, the electronic ballast on short circuit, open circuit, overvoltage, overcurrent and overtemperature protection easier, especially computer lamps in the application process dimming control features can be fully expressed.
7. in the volume and weight, the electronic ballast also have very significant advantages, the greater the advantage of power.
Electronic ballast is not without flaws, the cost is high, the circuit complex, on the production process, specification has strict requirements, such as power supply input current harmonic content and line power factor is two very important indicator. International Electrotechnical Commission has also formulated a IEC555-2, IEC61000-3-2 and other regulations, EN60555-Europe has developed 2 regulations, the Chinese Government has also developed national standards GB/T14549-93, and other regulations on electrical devices of voltage, current waveform distortion made specific restrictions and regulations.

With the switching power supply, electronic ballast, contributed to PFC (power factor correction) technology. PFC circuit is the basic principle of work through the control circuit forced input current tracking input voltage, input current sine and synchronize with input voltage, it functions as a pure resistance. Market better electronic ballast factor greater than 0.95 (around 0.98), harmonic content of less than 20 per cent of the total, the third-harmonic and other times the harmonic content of less than 10 per cent of the total, lamp current wave ratio less than 1.7, EMC IEC, cheap electronic ballast factor generally does not exceed 0.65, input current total harmonic distortion THD of up to 100 percent. It is not reaching the standard of electronic ballasts in use can cause any harm?
Electronic ballast for input supply current harmonic content is too high, if you are a used alone, the damage may not be able to clearly show it. But if the millions of intensive use, harmonic currents produced by the will to power system causing serious pollution, affecting the entire power system's electrical environment, including the power system itself and the majority of users. Excessive current harmonic makes the generator and motor generate additional power loss, causing fever; for reactive power compensation capacitor, give rise to resonance and harmonic current too high, causing power capacitor due excessively load or overvoltage damage; harmonic current increases the transformers and power loss; current harmonic content of electronic ballasts in the way of a power-intensive installation, three-phase four-wire line currents of power supply system has increased dramatically, far higher than the phase current, causing a midline overload, and can easily cause damage to electronic ballasts in a batch. In serious cases, will cause a fire, resulting in significant economic losses. Therefore, in terms of ensuring the safety of electric power system operation or from a protected user equipment and physical security, must be strictly limited current harmonic content, harmonic to reduce the serious harm caused by pollution.
Based on the above industry standards and strict technical requirements, many lighting factory also has a series of technical difficulties does not break, plus the cost is high, so many computer lamp manufacturers still using inductive ballast. While chaiyi light company in 2002 has boldly enabled switching power supply, electronic ballast, in stage lighting lineIndustry became the first person to eat crabs. Although early encounter some ups and downs, but after several years of experience and continuous improvement, chaiyi in this road yueshun. In 2008, chaiyi purchased 40 million detection equipment, designed to detect electronic ballasts, switching power supply of related technical indicators, to ensure that each batch of product shipment. Chaiyi light has now become a stage lighting industry "green lighting" leader.

】 【Weak current College (go) expert detailed professional audio troubleshooting tips (1).

Current professional audio equipment, upgrading is changing, so many devices in use which inevitably there are all sorts of trouble, some are on the device itself, and some of our audio division caused by improper use of the fault of the person, so we talk about the article: "professional sound system troubleshooting methods", I said failure is defined as "soft" fault, is designed for system operation in terms of failures, rarely involve real fault on the device itself, those considered "hard". I have always advocated the "professional", say what power amplifier is broken, Horn bad those are maintenance engineers, our sound engineer's job is to match a good sound system, the various sounds good, doesn't have to be jacks-of-all-trades! lift audio fault is really very painful because various fault really, very difficult in an article that clearly, I can only based on my years with various audio experience to fault of the article written in a simple pop up, I analyzed, generally sound kinds of system failure can be summarized as: total power failure, line failure, human operation breakdown, equipment failure, failure in itself, a total of five interference. The following is an analysis of a serve everyone, and this article explain also explains some troubleshooting audio, so we understand the cases it is even more simple and thorough.

A power failure, sound system

(A), total system power failure: in a previous article I made a sound system overall power profile is important to note the following points: 1, three-phase power: general use professional audio equipment for facilities will apply for the installation of three-phase power supply, the more important place also uses two separate three-phase power supply, just in case one fails so the whole system is down; even very important sites also use similar to PC "UPS" standby power, visible power is so important. 2, audio, lighting and power supply separately: this point in the previous article also told many times, sound system and lights it is best to have its own power, otherwise one is prone to interference, then a work is not secure. 3. total power distribution: light has a strong power is not enough, we must pay attention to the power of distribution: in principle, a mixer and a variety of audio sources equipment to have all the independent power; various peripheral equipment you want to have all the independent power; power amplifier and other equipment you need at least 2-channel independent power supply. Each one independent power supply with the corresponding air switch control, so we're switching equipment is very convenient.

(Ii), the device to a power failure: device itself power failures can also be divided into three parts: 1, device internal circuitry itself fails, the US General audio engineer can't exclude that need professional service personnel or equipment supplier to warranty. 2, power supply equipment, such as some DC-powered device to use a transformer, the transformer will fail sometimes; there is the power cord connected device has a problem, this situation rarely occurs, but also really good power line seems no problem is not powered on, and a power cable fault elimination. 3. patch equipment installations, such as device connected socket, power, timing, etc., the failure rate is very high in relative terms, especially in mobile performance to pay more attention.

(Iii), the power supply voltage, patch equipment failure: now better economic development, energy consumption is increasing, so the power supply voltage is very difficult to guarantee a constant standard, in this case many places using audio to hi-fi system is configured with a regulator, power equipment, but in the selection of devices it is important to note that regulator voltage power and quality; there are places with a power outlet or power source time series for quality rather poor, but also prone to failure. Power system failure case: 1, opened a new ballroom, the days debugging when voltage normal sound system, the system is working properly, but the evening performances, let alone the voltage low to 180 v, also some audio equipment is not working properly. I found this site using a three-phase power, sound system, a phase of lighting system and air conditioning system with a phase, other places a lighting system. When debugging a sound during the day in the ballroom of the lighting and air-conditioning are not open, therefore, power good, night, three-phase power imbalance issues came. Later, the air conditioning system is also a phase alone, the workplace lighting system using civilian electrical system, this three-phase power balance, you have resolved the problem. 2, a dance performance speakers are always issued "lol" the sound of impact, the results I found the quality of voltage regulator is not too good, whenever the regulator regulator pointer runout time speaker on "lol", and then replace the transformer, I found that sometimes there will be a power pulse sound, the results are found when pressing stage camera console, the sound is noise, then put the controller's power simply plug into civil electrical outlet, and ordinary mixer that road total power apart you have resolved the problem. The above example, we know the power failure is caused by a variety of, must rely on our careful installation, configuration and use, so the power part very critical and important.

【 Weak current College 】 unit size-n point---Power By 【 China power house network 】

Treble Cone diameter compression unit cell size of common AES power voice coil (and magnetic steel size relationships) common AES power voice coil nominal frequency point proposal (12-24dB/OCT) domestic unit recommended security-n frequency 25mm10-25w3kHZ3K34mm30-35w2.5KHZ2.8K44mm35-50w1.8KHZ-2.4KHZ2.4K50mm50w1.5KHZ-2KHZ65mm50-75w1.3KHZ-2KHZ72mm75-80w1KHZ-2KHZ1.8K75mm75-80w1KHZ-2KHZ1.8K76mm75-80w1KHZ-2KHZ1.8K100mm100-150w800HZ-1.8KHZ baritone unit cell diaphragm diameter common voice coil size AES power (and magnetic steel size relationships) 6.5 inch 44-50mm100-200w50mm 150w400HZ-8KHZ600-2K8 inch 50-inch and 50-65mm150-300w65mm 200w200HZ-6KHZ400-2K10 75mm150-450w75mm 350w150HZ-4KHZ300-1.5K12 inch 50-75mm200-450w100HZ-2KHZ100-1.5K bass unit cell diaphragm diameter common voice coil size AES power (and magnetic steel size relationships) 8 inch 50-150-75mm200-450w50mm 200w60HZ-2KHZ80-2K10 inch 50-200-100mm200-700w65mm 300w50HZ-2KHZ80-2K12 inch 50-350-100mm200-700w75mm 400w40HZ-2KHZ80-2K15 inch 65-100mm300-700w75mm 350-400w30HZ-2KHZ60-2K subwoofer unit cell diaphragm diameter common voice coil size AES power (and magnetic steel size relationships) 15 inch 75-600-100mm450-800w100mm 800w40-130HZ18 inch 75-600-100mm450-800w100mm 800w30-130HZ21 inch 100-600-800w30-130HZ 125mm600-1000w100mm