1. The speaker is the electrical signal into a sound signal of a device, restore authenticity as evaluation of the performance of important standard speakers. Active speaker system with power amplifier (PA) of the speaker system. The power amplifier and speaker system to make one, directly with the General sources (such as, CD, DVD player, VCR, etc.), a stereo mix. The active speaker, no other power amplifier, no longer as a reasonable selection of power amplifier, speakers and worry, simple operation, its high cost performance, as the generally accepted by the working class.

In accordance with sound principles and internal structure, the speaker can be divided into high-style, hermetic, flat plate, Horn, labyrinth, and so several types, where the main form is closed and down phase. Closed speaker is in a closed box above speakers, efficiency is lower; and phase-speakers and it differs is in the front or rear panel is fitted with a circular hole phase. It is in accordance with the Helmholtz resonator principle of work, the benefits of high sensitivity, can withstand the power of a large and dynamic range. Because the speakers to the back of the sound wave also released from the import phase holes, so its efficiency is higher than the closed-box. And the same speakers mounted on the appropriate phase box will be mounted on the same volume of airtight box got low frequency sound pressure higher than 3dB, which is beneficial to the performance of low-frequency section, so this is also the phase box to widely popular.

2. power speakers sound quality is good or bad and there is no direct relationship to power. Power of decision is speaker can emit a strong feeling loudly is sound on sound be. In accordance with international standards, there are two callout method: rating (RMS: sine wave root mean square) and transient peak power (PMPO power). The former is rated range driving a 8 Ω speaker provides continuous analog signal waveforms, in a certain interval and repeat a certain number of times, speakers without any damaged maximum power; the latter refers to the speakers short time the maximum power. The Federal Trade Commission in 1974 stipulates the power of the calibration standards: to drive a two-channel 8 Ω speaker load, in 20 ~ 20000Hz range harmonic distortion is less than 1% measured valid wattage for the amplifier output power, which had faded the embedded processing β shows ㄊ su Beach β province M ǔ I carbon Chair sou (Mutsumi NGAN hissing down bu bao ne pry cloth? peak) power, the General is rated power of about eight times. Imagine if the same is with PHILIPS TDA1521 power amplifier chip (maximum power rating 30W, THD = 10%), and some products called 360W, or even 480WP.M.P.O., this possible? meaningful? so when buying multimedia speaker system to the rated power. Speakers of power from the power amplifier chip power and power transformer of power both major decision, taking into account other factors, can calculate if the transformer rated power is 100W, it actually be driven power amplifier chip power to 45W, through computer speakers transformer and power amplifier power relations or verify the speaker of the actual rating is achieved nominal value. Speaker of the larger and more power is not a good is the best, for ordinary home users of 20 square meters or so room, a real sense of 60W power (refers to the speaker of the valid output power 30W× 2) is enough, but power amplifier for reserve power better, it's also a good idea to the actual power output of more than two times. For example, speaker out as 30W, the PA's ability to better than 60W, HiFi system, driver Hi-Fi amplifier power.

3. the frequency range and frequency response of the former refers to the sound system to be able to replay the minimum effective playback frequency and most significant playback frequency range; the latter refers to a constant voltage output audio signals and systems, speakers of acoustic pressure varies with frequency changes occurring increases or attenuation, phase frequency change phenomenon, this kind of sound pressure and phase and frequency of changes associated with the change in the relationship (), known as frequency response, in decibels (DB).

Audio frequency characteristics commonly used DB scale ordinate represents power and use logarithmic scale of the horizontal frequency of frequency response curve to describe. When sound power than normal power low-3dB, this power point known as the frequency response of high frequency cut-off point and low frequency cut-off point. High frequency cut-off point and low-frequency cut-off points between the frequency, the frequency response of the device; the phase lag of sound pressure and frequency of curve is called the amplitude and frequency "and" phase-frequency characteristics "," frequency ". This is a review of the merits of a sound performance indicator it and speaker performance and price point has a direct relationship, its DB lower notes sound frequency response smooth, distortion, the smaller, higher performance. As a speaker frequency response for 60Hz ~ 18kHz +/-3dB. These two concepts sometimes does not distinguish between that which is called the frequency response.

In theory, 20 ~ 20000Hz frequency response is enough. Below the 20Hz sound, although it will not be able to hear what other people can sense the senses, can feel the so-called bass, and therefore to play various musical instruments perfectly and language signals, amplifier to implement high-fidelity target to the harmonic tones are played out. So you should place the amplifier of CWI, the lower limit is extended to 20Hz following the upper limit should be increased to more than 20000Hz. For signal source (radio head, sound recording and CD player, etc) of the frequency response of representation. For example the European Broadcasting Union provisions of FM stereo broadcasting frequency response for 40-15000Hz 10/-2dB, International Electrotechnical Commission provisions on recording, the frequency response of a minimum specification: 40-12500Hz 10/10/-2.5-4.5dB (band), the actual can achieve the targets to be significantly above this value. The CD of the frequency response of up to 20000Hz, low frequency can be very low, only a few cycles per second, this is the CD playback quality is good.

However, constitute a sound of harmonic constituents is very complex, not the frequency range and wider sound good, but this is the middle of the basic multimedia speaker system is still correct. In the callout frequency response we usually see "system frequency response" and "amplifier frequency response," these two terms, to know the system frequency response "than" amplifier frequency response "range is small, so only tagging" amplifier frequency response, "it does not have any meaning, it is only used to deceive the consumers uninformed. Now the speaker manufacturers on system frequency response generally noted too large, and the high frequency portion of the poor are not very many, but the bass side callouts are not real, foreign brand HiFi (high fidelity) speaker but Callout 4, 50Hz, and three hundred wood normal speakers had dared to mark the data, really make people laugh their heads off! so must advise everyone to low frequency sound hearing is true, do not believe that propaganda on numeric values. The music in the multimedia speaker system is to play MP3 or CD of music, songs, games, sound effects, background music, as well as in the movie the human voice and environmental sound-based, these voices is to treble, in selecting a multimedia speaker system should be more like it in the performance of high frequency sound, rather than low frequency band. To really pursue a theater, then only enough of the subwoofer absolutely can meet your needs

16, total harmonic distortion (THD) means the audio signal source through power amplifier, due to the nonlinear components of the output signal than the input signal more harmonic constituents of extra. Harmonic distortion is due to the fact that the system is not entirely linear, we use the increased total harmonic composition of RMS and the original signal is expressed as a percentage of valid values. For example, an amplifier in the output when the 1000Hz 10V added Lv-2000Hz, 10 per cent of second harmonic distortion. All of the additional sum of harmonic level is called total harmonic distortion. In General, 1000Hz frequency THD minimum, so many products are based on the frequency of distortion as its target. But the total harmonic distortion and frequency, the u.s. Federal Trade Commission in 1974, total harmonic distortion must be 20 to the full audio 20000Hz determining the scope, and the maximum power amplifier must load of 8 European speakers, total harmonic distortion is less than 1% of the determination of the condition. International Electrotechnical Commission require total harmonic distortion of minimum requirements are: before 0.5 merge amplifier is less than or equal to 0.7%, but in fact can do the following: 0.1% FM Stereo Tuner is less than or equal to 1.5% actually do 0.5%; CD player can do 0.01 percent.

Because the current measure distortion method is a single sine wave, and do not reflect the amplifier in its entirety. The actual music signals are different rates for different composite wave, including rate conversion, transient response and dynamic index. It is a high-quality amplifier and sometimes annotated intermodulation distortion, transient distortion, transient intermodulation distortion and other parameters. (L) intermodulation distortion (IMD): the intermodulation distortion instrument output of 125Hz and lkHz of the resultant harmonic signal, by 4: 1 the amplitude of the input of the amplifier to be measured, from the rated load measured intermodulation distortion factor.

(2) transient distortion (TIM): the square wave signal input to the amplifier, its output waveform amplitude retention capacity to express. If the conversion rate of the amplifier is not enough, the square-wave signal will deform, but produce transient distortion. Mainly reflected in the rapid mutation signal of music, such as in a variety of percussion, piano, xylophone, etc., such as transient distortion large, crisp sound will become very confusing.

(3) transient intermodulation distortion: the 3.15kHz of the square wave signal and 15kHz of a sine wave signal peak amplitude ratio 4: 1 mixture, by amplifier, the new all intermodulation distortion of valid values and the percentage of the original sine amplitude. If amplifier using depth large loop negative feedback, transient intermodulation distortion is generally larger, specific reflect sound dull, blunt, no Telepresence; otherwise, voice and delicate, nature.

17, stereo separation between a two-channel does not interfere with the signal's ability and level, namely the isolation level, usually with a single channel within the signal level and escaped to another channel to the level of representation. If stereo separation, the icing on the cake will be undermined. International Electrotechnical Commission provisions of stereo separation minimum indicators, lKHz is greater than or equal to the actual 40dB, to achieve a good dry 60dB; European Broadcasting Union provisions of FM stereo broadcasting in stereo separation is > 25dB, actually practice 40dB above. Stereo channel balance refers to the left and right channel gain is the difference between the left and right channel output level difference between the maximum. If an imbalance is too large, stereo sound and image location will produce deviations from the specifications should be less than 1dB.

18, damping coefficient is an amplifier rated load (speakers) impedance and power amplifier that the ratio of actual impedance. Damping coefficient indicates power amplifier output resistance is small, damping coefficient is amplifier in signal disappears control speaker cone movement. High damping coefficient of amplifiers, speakers, more like a short circuit in the signal termination can reduce its vibration. Power amplifier output impedance will directly affect the speaker system low frequency Q value, which can affect system of low-frequency characteristics. Speaker system Q value should not be too high, usually in the range 0.5-l, power amplifier output impedance is the low-frequency Q the factors contributing to the increase in value, so you want power amplifier output impedance is small, the damping coefficient substantially better. Damping coefficient generally tens to hundreds of high quality, professional power amplifier of damping coefficient can be as high as 200 or more.

L9, equal-loudness control its role is to promote low-volume high and low frequency sound. Since the human ear on high-frequency sound, especially low frequency sound of auditory sensitivity is poor, and the requirements in low volume on high-frequency and low-frequency compensation for hearing, which requested the low frequency with larger, high-frequency is also a certain amount of promotion. In other words, when volume decreases, the low frequency portion of the signal to reduce a high frequency part. Equal-loudness control that meet this requirement, the equal-loudness control typically 8dB or 10dB.

Three-dimensional sound field dealing with 20, and surround sound common two speakers why would we hear and do not exist seem to be behind the sound of? as we all know, a film in three-d is the eye of illusion and the generation of three-dimensional sound field from the illusion of the ear. A variety of hardware 3D audio technology such as the SRS, virtual Dolby and software 3D technology such as EAX, A3D and so is fully examined the human ear accept sound principle is to reduce costs and introduces new technologies. In essence by many speakers complete three-dimensional sound field of results than two speakers virtual sound much better. So how should surround sound speaker configuration primarily, their location and spatial sense, let's take a look at what kind of true surround sound: A Dolby Pro-Logic directional logic (Dolby) surround sound system 4-2-4 encoding technology to left, Center, right, and the back side of the four aspects of audio information encoded records in the two-channel; playback then passed in from the left and right channels decoder decomposition restore previously this four-channel, four-channel is often referred to as: front left channel, lead the center channel, front right channel and rear surround channels. Scientific experiments have shown that, to obtain the true sound effects, it must be in the listener around a hems of acoustic environment, the entire lift system used by the channel number, the more listener panorama are, the more intense, more immersive experience. Under the existing General families of audio-visual environment, at the top of your system using the 5-channel has been able to meet the panorama, therefore, Dolby directional logic surround sound system mostly use 5 channels. On the surface, 5-channel Dolby directional logic surround amplifier does have five power output: front left channel, the channel, front right channel, surround left channel (also known as the rear left channel) and surround the right channel (also known as the rear right channel), but Dolby directional logic surround sound system in the surround sound decoder output signal is Mono, 5-channel power amplifier left two surround channels in internal amplifier is interconnected.

4, loudness, and the strength of the sound is called strength, it consists of a pressure rapidly changing amplitude (size determines the sound pressure). But the human ear on the strength of subjective and objective physical strength and inconsistent, people for the strength of perceived as loudness, its measurement unit for decibels (DB), which is the voice of 1000Hz at different intensities of sound pressure ratio, are commonly used on the value of l/10. Take on the value attributable to the increase in strength and loudness is proportional to the relationship, but the relationship between the number and logarithmic! for example sound intensity up to 10 times, the sounds they rang the level 1 (10dB), the strength to 100 times the sounds only two-level (20dB). For the voice signal, 1000Hz ear can feel of minimum sound pressure is 10E-5Pa, the sound pressure level as 0dB, when sound pressure over 130dB ear when you will be unable to stand, inquired as to the auditory dynamic range from 0 to 130dB.

People on the strength of equal, different sound frequency is different; the higher the sound pressure level, human auditory frequency characteristics more straight; the lower the sound pressure level, human auditory frequency range; frequency f (16-20Hz and f > 18 ~ 20KHz voice, no matter how high sound level, the human ear is inaudible. The old ear hearing frequency is 20Hz ~ 20KHz, this band is called the audio or audio; whether sound pressure, the human ear on 3KHz ~ 5KHz frequency of sound is the most sensitive.

Most people on signal sound level mutation 3dB below is feeling, and so on sound system often 3dB frequency response as allows curve range.

5. the distortion have harmonic distortion, intermodulation distortion and transient distortion. Harmonic distortion refers to sound playback in the original signal no harmonic constituents distortions; intermodulation distortion affected mainly sound tone; transient distortion is because the speakers have a certain degree of inertial mass is present, the basin of the vibration is unable to keep up with the transient changes an electrical shock caused by the original signal and playback sound differences between. It is in the speaker and the speaker system is even more important, directly affects the tone quality tone restore level, so the index and the quality of the sound box. This often percentage, smaller the number, the smaller the that represents the distortion. Common multimedia speaker of distortion to less than 0.5%, and usually a subwoofer distortion is generally larger, less than 5% is acceptable.

6, speakers of sensitivity (in DB) sound sensitivity each 3dB, output of poor sound pressure is off by a times, usually to 87 Db to 84 Db in sensitivity, low sensitivity, as 90 Db above for high sensitivity. Sensitivity enhancement is to increase the cost of distortion, as a high-fidelity speaker, to ensure that the restore level and tone reproduction must reduce the number of sensitivity. But not the other way round, sensitive speakers sound business and low sensitivity of speaker necessarily good. Low sensitivity of speaker amplifier is difficult to promote (requires power amplifier for standby power is large). So although the sensitivity is an indicator of sound, but it has nothing to do with speaker sound timbre.

7. impedance is the speaker of the input signal voltage and current for the ratio. Speaker input impedance generally consists of high impedance and low impedance two classes, higher than 16 Ω is high impedance, less than 8 ω is a low-impedance, speakers of standard impedance is 8 Ω. The power amplifier with power output in the same circumstances, low impedance of the speakers can get a larger output power, but impedance is too low and cause deterioration due to the damping and bass. So although this indicator box is unrelated to the performance, but it's still a good idea not to buy low-impedance of the speaker, the recommended value is a standard 8 Ω. Impedance headphones are generally high impedance-32 Ω is very common. The impedance of the amplifier can be marked as equivalent impedance, such as 4 Ω output under 130W, in equating 80W output. There is an easy and confusing term called "damping factor", which refers to the speaker impedance source of internal resistance, divided by the amplifier, the range is about 25 ~ 1000. The speaker cone in electrical signals have disappeared after oscillation many completely stopped swinging and coil voltage current issued and magnetic field can prevent this parasitic movement, this is the damping. Current amplitude is the damping effect depends upon whether the current flowing through the amplifier output stage of internal resistance, the resistance to well below the speakers rated impedance, the typical value of 0.1 Ω, but because the speaker voice coil of series resistance and crossover network series resistance, damping coefficient difficult 50.

8, signal to noise ratio is a sound playback of normal sound signal and no signal noise signal (power) ratio. Also used Db representation. For example, a tape recording of 50dB signal to noise ratio for, that is, the output signal power than noise power large 50dB. The higher the SNR value, the less noise. International Electrotechnical Commission-to-noise ratio of the minimum requirement is a preamplifier is greater than or equal to 63dB, after the preamplifier is greater than or equal to 86dB, merge-amplifier is greater than or equal to 63dB. Merge-to-noise ratio of amplifier is in the best value should be greater than 90dB; radio head: FM stereo of 50dB, actually to achieve better 70dB above; magnetic tape sound recording seat of 56dB (band), but with Dolby noise reduction-to-noise ratio has greatly improved. As Dolby noise reduction of B-to-noise ratio up to 65dB, C by Dolby noise reduction its signal to noise ratio up to 72dB (none of the above means band); CD-to-noise ratio can reach over 90dB, top-of-the-line more than up to l10dB. Signal to noise ratio is low, small-signal input noise, the entire range of sounds obvious is cloudy, so-to-noise ratio is lower than the speaker does not recommend 80dB purchase! and subwoofer 70 DB subwoofer same reasons we do not recommend that you purchase.

9. the speaker materials because of their low quality plastic speaker cabinet and ill-considered, cannot overcome resonant, with no sound at all (benbenxiong Note: isn't that design good plastic speakers to far better than poor quality wooden speakers); wooden speakers reduces cabinet resonances caused by bass, sound quality is generally better than plastic speakers. Typically multimedia speaker system is two-module 2, featuring design, a small speaker responsible for treble output and another larger speaker is responsible for the bass output. Selected speakers should consider both the Horn of material: multimedia active speaker of treble unit is now mainly soft ball (as well as for analog audio source of titanium ball, etc), which, in conjunction with digital audio sources reduces the high-frequency signal into feeling, to give a soft, smooth, and smooth feel. Multimedia speaker system is to better the quality of silk-and lower-cost PV film and other soft ball. Bass unit that determines the speaker's voice features, select up relative importance, the most common include the following: Cone, packing tape, paper-based wool basins, tighter several pressing bowls, cone timbre nature, cheap, better stiffness, material lighter high sensitivity, the disadvantage is moist and manufacturing time consistency makes it difficult to control, but top-level HiFi system using cone manufactured there, because the sound output very average, restore the good; bullet-proof fabrics, have a wide frequency response and low distortion, for strong bass's preferred, disadvantage is costly, complex manufacturing process, sensitivity, effect is not very high light music; wool weaving basin, than that on the soft music and light music performance is outstanding, but the bass was poor, lack of strength and shock force; PP (pp), it is widely popular in the high-end speaker systems, consistency is distorted and low performance are subtle. In addition, like fiber cone and composite Cone, etc. because prices are rarely applied in popular speaker, just not on. Speaker size natural is better, large-diameter bass speakers are in the low frequency portion has better performance, this is optional, you can select. With high-performance speaker manufacturing speakers means lower transient distortion and better sound quality. Common multimedia speaker bass speaker Horn typically 3 to 5 inches wide. With high-performance speaker manufacturing speakers also means lower transient distortion and better sound quality.

10, speakers of structure and features speakers from structural forms, can be divided into the Bookshelf and former ground-mounted, compact, hierarchical clear, precise positioning, but power limited, low frequency extension and quantity was suited to appreciate to high-fidelity music oriented music lovers, but also our multimedia enthusiasts preferred; the latter large, with a larger carrying power, low-volume and elasticity of strong, good pouring the vehemence and powerful shock force, but not done well depth and orientation is somewhat lacking. For different music enthusiasts, this is also what you should know before buying. As PC users rarely have placed large landing conditions, so that the small desktop shelf-speakers should be multimedia active speaker preferred. In General: as long as the reasonable power amplifier module design, the greater the Horn, the larger box, sound is heard.

11, scalability, and it is the speaker supports multichannel input, whether received passive satellites output interface, if there is USB input features, and more. The subwoofer can add the number of satellites is a measure of performance standards. Common multimedia speaker interface has an analogue interface and a USB interface, such as fiber interface and innovative dedicated digital interface, and so is not a very rare, so there is no more.

12, sound technology hardware 3D audio technology now more common with SRS, APX, Spatializer 3D, Q-SOUND, Ymersion, Dolby and Virtaul several, each of them to implement different, but can make people feel the obvious effect of three-dimensional sound field, and three more common before. They apply are extended stereo (Extended Stereo) in theory, this is accomplished by the circuit on the sound signal for additional processing, the felt sound like position extends to the outside of the two speakers, for sound like an extended, so that people have a sense of openness and the icing on the cake, produce wider stereo sound. In addition there are two audio enhancement technology: active servo technology (essentially use the Helmholtz resonance theory), BBE High definition high left to replay system technology, and the phase by fax, on improving sound quality also has certain effects. For multimedia speakers, SRS and BBE two technologies easier to achieve the effect of a good, effective in improving the performance of the sound box.

13. notes that have a specific and are usually stable pitch of signal, popular speakers is to tune and low sounds. It largely depends on the frequency, and intensity of the sound. High frequency sound human ear response is high and low frequency tone of voice response of the ear is the pitch. Tone with the frequency (Hz) change basically is logarithmic relationship. Different instruments playing the same note, the frequency of the tone, but they tune is the same, that is, playing a sound base frequency is the same.

14, timbre to the sound-quality feel, it is also a voice from another characteristic of sound quality. Different instruments in the same tone, their colors can meet so different. This is due to their fundamental frequency is the same, but the harmonic constituents considerably. So the tone not only depends on the pitch, and fundamental frequency multiples of harmonic formation, closely related, which makes each instrument and everyone has a different timbre.

15, dynamic range sound in the strongest and weakest ratio, expressed in Db. For example, a band of dynamic range to 90dB, which means that the weakest part of the power than most parts of the low 90dB. Dynamic range is a ratio of power, and the absolute level of sound. As mentioned earlier, the human ear's dynamic range from 0 to 130dB. Nature sounds of the dynamic range of variation is very great. General language signal is only about 20 ~ 45dB, some symphonies of dynamic range up to 30 ～ 130dB or higher. But as some of the factors, the sound system of dynamic range rarely achieve the band's dynamic range. The recording device for internal noise determines the weakest may be recorded, and the system sound of maximum signal capacity (distortion level) limits the strongest tone. In general the sound signal to 100dB dynamic range, so the dynamic range of audio equipment can do 100dB, very good.