Speaker twenty questions

Although the speaker is the most important part of the audio replay, it is the most misunderstood. Some HIFI fans are also often misled by those who think they know more, so here I directly list the answers to some of the most "sensitive" questions.

Is it necessary to buy special home theater speakers? Or can the stereo speakers be competent for the main left and right speakers?

If you have a pair of excellent stereo speakers that you can keep, they must be better than inferior home theater speakers. But you need to understand that the design requirements of an ideal home theater speaker are different from traditional stereo speakers. Generally speaking, stereo speakers are designed to radiate sound at a wider angle in the horizontal and vertical directions than the front speakers in home theaters. Their maximum efficiency response is along each speaker axis. For channel stereo, the above characteristics can result in the best mixing of the direct sound from each speaker and the reflected sound from the room. On the other hand, many home theater front speakers are designed to carefully limit the vertical dispersion of sound to a small angle, resulting in a reduction in the reflection of sound from the ceiling and floor. The design is to diffuse sound broadly so as to be able to produce more ambient atmosphere than you can feel from the "normal" front left and right speakers.

Why does the home theater need to add a center channel speaker and the stereo does not have it?

Do you need a center channel speaker? You try to listen to a record of a musician performing solo (singing) on ​​the stage from the left, middle, and right of the room. The soloist's image will change as your listening position changes. This kind of directional distortion is unacceptable in a home theater, because the picture tells you one thing, and the ear hears another. The solution is to set up an independent central speaker, and the sound of the middle scene is directly emitted by it.

What frequency range does the surround back speaker handle?

For Dolby surround sound recording, the standard frequency bandwidth is 70 Hz to 8 kHz. Although some sound tracks may also have frequencies as low as 50 Hz or lower. In 5.1-channel Dolby digital recording, the surround sound signal may be full-frequency, but most surround sound processors direct any low frequencies in the surround channel to a special subwoofer output. There it is combined with the components of the low-frequency effect channel (LFEa.ka ".1"). So before you buy a subwoofer, you can use small surround speakers that were not originally designed to produce deep bass.

What is the difference between 5.1-channel Dolby Digital Surround System speakers and Dolby Pro Logic System speakers?

If these speakers have sufficient high frequency response (most of them are available), it can be used for both. If there is subwoofer, pay attention to the deep bass to subwoofer.

Must the center speaker and surround speakers be driven with the same amount of power as the front left and right speakers? For 5.1 channels, surround speakers should require the same maximum output power as the three front speakers (left, center, and right). In order to cover all bass, it is best that all amplifiers have equal power. It is assumed that the front speakers and surround speakers have the same sensitivity and listener distance. (Low-sensitivity surround speakers require more power to reach the front speakers). The most important home theater is the center speaker. In order to get balanced sound, this speaker must be of good quality, and the driving power must be equal to that of other speakers.

What is a dipole speaker? How many "poles" does it have?

A dipole loudspeaker is a type of loudspeaker in which the sound waves emitted from the front are the same as the sound waves emitted from the back but opposite. The side sound waves of this kind of speaker are zero because the sound waves coming and going cancel each other out. The dipole speakers of home theaters are usually designed to be hung on the wall, and their zero points are directed to the listening area, while the directly radiated sound waves are directed to the front and rear walls, and only the reflection of the wall reaches the ear of the listener, so that it is difficult for the listener to hear Where does the sound come from. (The purpose of surround sound is to make the sound surround you all around!) Home theater dipole speakers usually have two push units in opposite directions, one forward and one backward. The front of the speaker toward the listening position usually does not push the unit. In contrast, huge flat dipole speakers (such as electrostatic speakers) are usually matched with high-end audio. Its position is such that the listener is on the main axis of sound emission, the front output is heard as direct sound, and the out-of-phase rear output is reflected by the wall behind the speaker. Bipole speakers are similar to dipole speakers, but the sound waves emitted before and after are in phase. The two overlap each other at the edge, which not only does not cancel, but enhances the bass output.

Conventional speakers have all the push units installed on one side, and it can be called "monopole". You can also design "multi" pole speakers arbitrarily, but "multi" pole types may not produce better or different sound effects. Some listeners prefer direct-radiation monopole speakers rather than dipole speakers such as surround sound speakers. Some surround sound speakers can be switched to dipole format or bipolar format to adapt to different program materials, environments or hobbies.

My listening position is at the back of the room, with the back facing the wall. How should I set up my home theater to play multi-channel (surround sound coding) music?

This is not the best arrangement. But if you put the surround sound speakers relatively high on both sides of the wall. Facing and covering the entire listening area, so you can get good results. If the dipole surround speakers are placed at an angle so that the zero point is aligned with the listening area, they can be placed further down and in front of the side wall.

When playing a CD in a home theater, should it be converted to a stereo format for listening? I know that many people think it should be converted to two-channel stereo, because it is "as it is". But I said you might as well try both. You will find that when Dolby directional logic is used or when the center and surround speakers are added to create a live atmosphere, the music sounds more natural. A few years ago, an editor of "Stereo Review" and the author of this article hosted a closed-eye test at an annual meeting of the Audio Engineering Society. When playing stereo programs, most engineers believe that directional logic sound is better than two-channel stereo.

What is the difference between biwiring and biamping?

When the speakers are wired in two ways, connect the two wires of one channel of the amplifier to the corresponding speakers. A speaker that can be wired in two ways has two sets of inputs. If the speaker is not a two-way connection, these two sets of terminals are connected by metal sheets. As you can imagine, in both cases, the circuit is the same, so there is no benefit in two-way wiring.

Two-way amplification is quite another matter, requiring two separate amplifiers to drive the woofer and tweeter. If you use the first variation-what I call "Parallet Amplification"-each amplifier is just supplied with the same input, I think it is almost useless as a two-way connection-each amplifier is Work less.

The second variation is that the line level output from the active crossover network is sent to the amplifier, one for low frequency and one for high frequency. Then the low-frequency amplifier directly drives the woofer, while the other amplifiers push the tweeter (or high-frequency hardware). This approach is definitely meaningful because it replaces the original passive crossover network of the speaker with an active crossover network. This technology is only commercially available after the emergence of home theaters. It takes the form of a high-pass filter in the surround sound decoder and a low-pass filter in the active subwoofer.

Why are some speakers so huge?

And I have seen some small square speakers that can solve the placement problem? Larger bass units require lower amplifier power than smaller bass units, but produce lower and louder bass with less distortion. Therefore, if you need truly accurate sound or more bass, and the listening room has enough area to fit, the bigger the woofer, the better. The biggest function of "Small Square" is to match the subwoofer to make the sound softer.

Why does the room have such a big influence on the sound of the speaker system?

This is because you have to listen to each sound more than once, first directly from the speaker, then reflected and reverberated by the boundary (wall) of the room. This is not a bad thing. Stereo sound is the sound of a "live" room with pleasant reverb characteristics, which is better than in "dead" rooms with no or almost no reverb ) Much nicer. However, film dubbing is usually better in a room with less reverb, because the content of the program material has added a live atmosphere in the surround sound part. The acoustic environment of a good movie theater is far more “dead” than a good concert hall. If it is a performance with heavy bass, the house itself will tolerate and enhance the bass output. Without walls, ceilings and floors, we will need a much more powerful woofer. If you do n’t believe it, try to put the speaker outdoors, you can feel how much its audible bass output is reduced.

A friend reminded me not to use an equalizer, not even a high and low sound controller. But my sound system has a sound quality that seems to be exaggerated, I really want to remove it.

I thought it might be better to use balance. Among high-end audio fans, it is considered bad to overuse equalization reputation. In a perfect world, playing music should not require balance, unless it is adapted to a particular hobby. But in the real world, every room affects the low frequency response in an irregular way, and you can often use the equalizer carefully in one position to improve the sound quality. But you cannot make the sound quality of the whole room very good. Equalization does not treat poor-quality rooms or poor-quality speaker systems. When a suitable speaker is placed in the best position, the proper amount of equalization can improve the bass and lower mid-frequency (the treble is less noticeable). Even if you use a test instrument, you still have to rely on the human ear to obtain natural sound.

I have seen some tall flat speakers. How do these speakers work?

These may be electrostatic speakers or flat magnetic speakers. Height and flatness are the natural requirements for their design. This type of speaker is appreciated by people for its accurate audio-visual positioning and stereoscopic space reproduction, which is a high and flat speaker transmission method. But it may not be suitable for use as a front speaker. Although it is thin, it does not save space. Because it must be hung at a certain distance from the wall for good sound, it still takes up a lot of area.

What are the advantages of horn speakers?

In the early days of HIFI audio, amplifiers were very expensive, and horn speakers were very common because they could vibrate cones or domes with smaller amplifier power to make louder sounds. High-power amplifiers are now quite cheap, and speaker efficiency is no longer so important, mainly because horn-type speakers can control the direction, so they continue to be used. A carefully designed shallow horn IF or HF unit can extend the audio response, increase power control capabilities, and improve the uniformity of the radiation pattern.

Some speakers cost more than US $ 10,000 per pair, what quality do they have that a speaker at a price of one-tenth does not have?

Most listeners (including myself) will be impressed by the wonderful sound quality of the most expensive speakers. These speakers must have something special. Due in part to the quality of its components and the materials used, a woofer using a Kapton-type coil holder and an edge-wound square aluminum wire is better than a woofer made of special paper and round copper wire. Much more expensive. Secondly, the speaker paint used for the ten thousand yuan speaker is equivalent to the paint used for valuable furniture. Third, the manufacture, distribution, and retail of top-level speakers are not carried out in batches, which is not cost-effective. It can be said that it is expensive because few people buy it. This phenomenon frustrated manufacturers.

I heard that using an amplifier with too little power will damage the speakers. Is this correct?

This is a kind of old talk that is often heard, and it keeps repeating until people believe it. There is a theory that using a low frequency signal to clip a small amplifier will generate some energy in the range of the tweeter. Therefore, people are usually advised to use higher power amplifiers to avoid burning the tweeter due to clipping. In fact, that makes no sense! If a small amplifier will burn it, a large amplifier will burn it more quickly! I have a pair of speakers that have been in use for twenty years, and the foam around the woofer has become sticky.

Which speaker should I buy today?

The question of what material to choose for the support of the speaker cone edge need not be described in detail. Loudspeaker manufacturers tell me that any additives used in foam plastics can increase the protection against ozone or ultraviolet rays. Some advertisements or magazine articles also talk about repairing the surroundings of the speaker, you may wish to consider it before buying the speaker.

A friend of mine put some small objects on the top of the speaker, or between the speaker and its bracket, saying that this will make the sound better, can you explain the reason for its improved sound quality? People are full of room for self-imagination, and ignorance will bring fantasy, but science opposes ignorance. This assumption is very easy to determine, if you try to put things and take things away under closed-eye conditions, can you distinguish the sound, and blindfolded to tell others to master the switch without telling you what he did, if You ca n’t hear the difference after doing countless tests, there is no reason to put anything on the speaker.

How to set the subwoofer level (loudness)?

This is a subjective determination, not a technical argument, so it can be determined by ear audition. For the audition material, I recommend using an orchestral CD instead of film dubbing because it has too many explosions like sound effect. You pay attention to listening to the part of the bass sound from the upper bass to the subwoofer. You must not hear the subwoofer as an independent source. The bass instrument should not be buzzing, and the bass vocal should not be moaning.

Most subwoofers have several control switches to help you mix it naturally with the sound of the main speakers. These control switches are: a volume knob; a crossover controller; and sometimes a "phase" and polarity controller. The location of these controllers and subwoofers must be determined by field audition.

Where does the subwoofer perform best?

Placing the subwoofer in a corner of a rectangular room will definitely excite the room's natural acoustic "mode" or resonant frequency, resulting in maximum output. If it is not convenient. It can also be placed in other places and listen to the degree of coordination between it and other speakers and the degree of distortion at maximum output until you are satisfied. Unless the location is impossible, the general subwoofer should be placed in the corner to listen first.

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