【 Weak current College 】 speakers fundamentals--Power By 【 China power house network 】

The speaker is a turn signal is converted into sound signal of electro-acoustic devices. Specifically, the speaker of the work is actually put a range of audio power signal transducer mode transition as low distortion and has enough sound pressure level of the sound can be heard.

Many types of speakers, classification is also very diverse, according to their works, the diaphragm shape and burst frequency range to sort.

Construction of a, speakers

Our most common electric tapered cone speakers. Electrodynamic type cone speakers in the past we often say that paper cone speakers, although now with cone Cone, but at the same time many polymer diaphragm, metal diaphragm, cone speakers call it worthy. Tapered cone speakers generally consists of a magnetic loop system (permanent magnet, magnetic core column, plates), vibration system (Cone, voice coil) and auxiliary systems (centering force tablets, basin rack, cushions) and most of the form.

1, voice coil: voice coil is cone-shaped Cone Speaker driver unit, it is a very thin copper wire in two layer around the tube, General-around dozens of times, is placed in the import core columns and magnetic plate consisting of magnetic suspected gap. Voice coil and cone fixation with the sound current signal access voice coil, paper voice coil vibration led a basin vibration.

2, Cone: tapered cone speakers of conical diaphragm material used in many types, there are natural and artificial fibres. Natural fibers often used cotton, wood, wool, silk, rayon, just use rayon, nylon, fiber glass, etc. Because of the cone is sound radiation device, to a considerable extent, determine the speakers at the performance, so no matter what kind of paper, which Bowl light and rigid good, not because of the ambient temperature and humidity changes.

3. fold the link: folding ring is to ensure the paper trough along the axial movement of the speakers, limit the set of lateral movement and, at the same timeserve to block the cone and the circulation of air dare. Pack ring material subject to standard cone material, but also the use of plastics, natural rubber, heat bonding paper cone.

4, centering force tablets: centering force tablets to support voice coil and the combination of the cone, ensure its vertical not skewed. Centering force on many concentric ring so that the voice coil in the magnetic gap in the freedom to move without lateral movement to ensure that the voice coil not met with magnetic plate. Centering force on dust cover to prevent external magnetic gap dust off, avoid creating dust and the voice coil friction produces abnormal sound speakers.

Second, the classification of the acoustic field

Classification according to the principle of work: the working principle, the speakers are divided into electric speakers, electromagnetic speaker, electrostatic speakers and piezoelectric speaker, etc.

1. electric speakers: this speaker uses power conductor for the voice coil, when entering an audio voice coil current signal, voice coil is equivalent to a current-carrying conductors. If you place it in a fixed magnetic field, depending on the current-carrying conductors in the magnetic field will be affected by the force and motion, voice coil will be a size and audio is proportional to the electric current, direction with audio current changes. In this way, the voice coil in the magnetic field generated vibration and driven diaphragm vibration of air before and after the diaphragm is vibration, this electrical signal is converted into acoustic radiation around. The speakers are the most widely used.

2. electromagnetic speaker: also called Reed-speakers, sound source signal current through the coil will put the soft iron material magnetic Reed, magnetized by vibration Reed and magnet attraction or drain down, driving force, so that the diaphragm vibration and pronunciation.

3. electrostatic loudspeaker: the loudspeaker takes advantage of the principle that the forthcoming electric capacitance diaphragm and fixed electrode configuration reverse polarity, forming a capacitor. The sound source signal in addition to this capacitance of the Poles, a room for the attractiveness of the electric field intensity changes, thus driven diaphragm vibration audible.

4, piezoelectric speaker: using piezoelectric material subjected to electric field theory of deformation, the pressure of electric components in audio form of electric current signal so that it occurs in the displacement, resulting in inverse voltage effect, finally driven diaphragm.
The diaphragm shape classification: speaker has a cone and plate-shaped, ball-shaped, Ribbon-shaped, flake, etc.

1, conical diaphragm speaker: conical diaphragm speaker in the most widely used is the conical cone speakers, its diaphragm into the cone-shaped, is most common in the electrodynamic loudspeakers, the most widely used by speakers, especially as the bass speakers most widely applied.

2. flat panel speakers: is also a kind of electrodynamic loudspeakers, it is the plane of the diaphragm to the overall vibration sound directly to external radiation. It's flat diaphragm is a circular peak nest boards, plate is made of foil peak nest-core, the two sides covered with fiberglass. It's frequency characteristic flatter, frequency bandwidth and low distortion, but rated smaller.

3, ball-shaped speakers: ball-shaped speakers are an electrodynamic loudspeakers, it works the same as with the paper cone speakers. Ball-shaped speaker's distinguishing feature is the transient response and low distortion, links to good, but inefficient some, often as a speaker system for use in the treble range.

4, Horn loudspeakers: Horn loudspeakers works and electric paper cone speakers. The diaphragm Horn loudspeakers are ball-shaped or other shapes. The speakers and other speakers of the main differences is that it's sound radiation pattern, cone speakers and a ball of loudspeakers is encouraged by the diaphragm direct air around the sound radiation out of, is the direct radiation, while the Horn loudspeakers are to produce sound by vibrating the trumpet radiation into space, is an indirect radiation. Horn loudspeakers biggest advantage is high efficiency, harmonic distortion is small and direction, but the band is narrow, low-frequency response. So much as a speaker system for use in the treble range.

Press playback frequency: can be divided into bass speakers, audio speakers, treble speakers, full band speakers, etc.
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1. bass speaker: speaker playback low-frequency signal is called a woofer, bass performance is very good. Bass speakers for the lower-frequency playback extends as far as possible, thus down speaker diameter have done relatively large, usually have 200mm, 300-380mm different diameter specifications of the woofer, with large input power. In order to raise the vibration amplitude of cone-volume limits, often using soft, wide support, such as a rubber edge, edge, insulating edges, etc. In General, the larger the diameter woofer, replay of low frequency sound better, the input power.

2, baritone speakers: main speaker playback if signal is called audio speakers. Audio speaker can achieve Woofer and treble speaker playback music at the frequency of convergence. Because if the entire range of leading range, and the human ear on the frequency of feeling more sensitive to other frequency bands and therefore misses the speakers sound requirements. A cone-shaped, ball-shaped and, cylinder, type. As the main audio speakers, performance requirements is the sound pressure level frequency response curve assumed, low distortion, links to good.

3, treble speakers: speaker playback high-frequency signal is called a treble speaker. Treble speakers for high frequency playback limit frequency pass up human auditory limit frequency 20kHz, Aperture smaller, less tough membranes. And low, compared to treble tenor speakers speaker performance requirements are the same except and baritone unit, also called the replay band limit to high, input capacity. Commonly used to high-pitched speakers with cone-shaped, flat shape, ball-shaped, Ribbon Capacitance-type and other forms.

4, full-band speakers: full band speakers refers to the ability to also cover bass, tenor and treble the band speakers, you can play the entire audio range of the signal. Its theoretical frequency range is from dozens of Hz to 20kHz, but in fact as a speaker is very difficult, and most of all to make dual-cone speakers or coaxial speakers. Dual Cone Speaker is in the middle of the large-caliber speakers plus a small caliber of cone, used to replay the high frequency sound signal, thus it¡¯s helpful for the frequency response limit values. Coaxial speakers are two different-diameter Woofer and treble speakers installed on the same axis.

Third, the speaker's performance indicators

The speaker is a speaker system (commonly known as speakers) of the key parts of the quality of the speakers were mainly by speakers of performance indicators, decision determines the set of indicators for playback. Speaker's performance indicators are rated power, rated impedance, frequency response, harmonic distortion, sensitivity, nature, etc.

Speakers and disadvantages of performance, primarily through the following indicators to measure:

1, rated power (W)

Speakers of the rated power refers to the speaker to work long hours of output power, also known as no distortion power, it is generally marked on the nameplate of the speakers on the back end. When the speakers work at rated power, voice coil will not produce excessive heat or mechanical phenomena such as dynamic overload, the sound does not appear distorted. Rating is an average power, but in fact speakers work in variable power status, with the input audio signal or weak, weak music and soundsignals, peak pulse signal exceeds the rated power many times, because of the short-duration without damage to speakers, but may appear distorted. Therefore, to ensure that in the peak pulse appears still get good sound quality, the speaker needs to remain enough power. General speaker can vary according to the maximum power is the rated power of 2-4 times.

2. frequency response (Hz)

Is a measure of frequency characteristics of speakers to put audio bandwidth of indicators. High-fidelity playback system requirements for speaker system should be able to replay 20Hz-2000Hz human ears to hear its range. Because single-only speakers are not easy to realize the range, the current high-fidelity sound system with high, medium, low three speakers to realize the entire replay cover bands. In addition, high-fidelity speaker frequency characteristics should tend to be flat, otherwise would introduce a replay of frequency distortion. High-fidelity playback system requirements for speakers in playback frequency range frequency flatness is less than 10dB.

3. rated impedance (Ω)

Speaker impedance rating refers to the speaker in rated State, applied to the speaker input voltage and electrical current flowing through the speakers of the ratio. Now, the speakers rated impedance generally have 2, 4, 8, 16, 32, Europe, etc.
Speakers rated impedance is the input signal voltage 400Hz situations measured, and the speaker voice coil of DC resistance R direct ≈ 0.9R places.

4, total harmonic distortion (TMD%)

Speaker there are many kinds of distortion, common harmonic distortion (multiple non-uniform magnetic field by the speakers and the distortion of the vibration system, often resulting in low frequency generated), intermodulation distortion (because two different frequencies of the signal simultaneously to join speakers, mutual modulation induced sound deterioration) and transient distortion (due to the inertia of the vibration system cannotkeep up with the signal, thus causing signal distortion). Harmonic distortion is the replay, increases the original signal harmonic component in no time. Speakers of harmonic distortion comes from non-uniform magnetic field of magnets, vibrating membrane characteristics, voice coil displacement nonlinear distortion. At present, better target for harmonic distortion of the speakers is not more than 5%.

5, sensitivity (dB/W)

Speaker sensitivity typically refers to the input power voltage noise for 1W, in front of the speakers axial 1m premises measured sound pressure. Sensitivity is a measure of the speakers to the audio signal details can exhaustively replay indicators. The higher the sensitivity, the speakers to the audio signal of all the details can make a response. As Hi-Fi speakers of sensitivity should be greater than 86dB/W.

6. directivity

Speakers on different directions of radiation, its sound pressure frequency characteristics are different, this feature is called speaker directivity. It and cryWith Aperture, diameter large directional tip, diameter hours directed wide. Directivity and frequency, in General, for low frequency signals below 250Hz, no clear direction. On the high-frequency signal 1.5kHz following the obvious direction.