Also talk about the placement and setting of the home theater overweight subwoofer

[Home Theater Network HDAV.com.cn] When you carefully adjust a home theater system, you should find the best position for the subwoofer, so that the home theater system achieves the best combination and sound effects for home theater. This has always been a big challenge for users.

In this challenge, two factors are indispensable, the boundaries of the listening room surrounding the listening area and the ability of the air surrounded by these boundaries to store energy. The combination of these two factors determines the unique acoustic properties of the listening area.

Repeated testing is the key and practical way to get the best sound. There is no perfect position in reality, you can only find those that are close to perfect. You need to draw a lot of sketches and make some compromises in some areas. Compromise is not only the result of the acoustic characteristics of the listening room, but also aesthetic, practical and other considerations, such as the wife's preference, you can not be inappropriate. In some families, the wife's preference may be the most decisive factor.

The tricks taught here do not require any type of measuring instrument, you only need to bring a pair of ears to get everything done. Of course, you also have the most basic test signals, such as a test CD, or a music CD with a lot of low-frequency content. If you have an instrument that can accurately measure sound pressure, of course it is best; but if you don't, don't worry, we have our own tricks.

First, the control of the listening room

Many people are proud of the "ideal size" of their listening rooms. In general, the larger the area of ​​the listening room, the less the low frequency standing wave can hear. In order to obtain a smooth and balanced low-frequency sound, the ceiling of the listening room should be no less than 3 meters, the width should be no less than 3.6 meters, and the length should be no less than 7.5 meters (if you want a deeper low frequency, you must be no less than 9.1). Meter). The length of each side of the listening room (including the diagonal) should not be an integer multiple of the wavelength of the sound wave, otherwise resonance will occur. Of course, the larger the listening room, the more sound-absorbing facilities are needed to reduce the time of sound reflection, but standing waves are generally not formed in the large listening room.

Another important point is the use of sound absorbing materials, so that the decay time of the low frequency is generally the same as the intermediate frequency and high frequency. This is what people call a "neutral listening room." The light and flexible walls act as good sound-absorbing walls, where low-frequency sounds will pass through the walls and never reflect. This effect can be achieved by walls constructed of gypsum board, wood and double-layered stone in the correct structure. A world-class listening room usually requires the use of sound/scatter materials to eliminate resonance or echo. Beware of small holes in the walls, they can also cause resonance. It is the skill of a professional sound engineer to build a large listening room with good low frequency response, correct internal acoustic characteristics and excellent external sound insulation.

Second, the placement of the speaker - use foot nails or isolation pads?

The speaker can be mounted in a small hole in the wall, and the front panel of the speaker is flush with the wall. This type of installation requires the skills of a professional sound engineer, and we don't have much discussion. The main speaker must be decoupled from the floor. The heavy and hard tripod has a top that is no larger than the bottom of the speaker to avoid diffraction of the sound (this is a type of comb filter). The studs have a good stabilizing effect, but it is easy to puncture the carpet when using the carpet.

Some people recommend padding a floor mat instead of a foot under a heavy speaker. Regardless of the placement method, the goal is to reduce synchronous resonance or to reduce the transmission of sound waves between the cabinet, the floor and the wall. The resonant frequency of the cabinet and the stand should be very low. Knock on the box with your fist, make sure it doesn't have a resonant characteristic, input a sine wave signal to your sound system, and listen to the box to see if there is any vibration.

Third, the positioning of the speaker

Before placing the subwoofer speaker, we assume that: (1) you have a healthy ear that can evaluate the acoustic characteristics of your listening room; (2) unless you specifically declare that you are using two overweights Subwoofer; (3) You have enough test signal software to test the characteristics of the sound field you hear at the listening position, and how the listening room affects the sound; (4) All necessary corrections for the sound system It has been completed.

The placement and correction of the subwoofer can be divided into 5 steps:

1. Adjustment of the position of the subwoofer; 2. Adjustment of the seat of the listener; 3. Phase adjustment between the main speaker and the subwoofer; 4. Equalization of various parameters; 5. Gain of the subwoofer and the main speaker match. Home theater network shopping guide network welcomes you!

I have seen different ways to systematically adjust the sound system in a listening room to determine the optimal placement of multiple subwoofers. Here is one of the methods:

This is a process that requires trial and error, and you may want to listen to the same content over and over again. When you are bored, sit down and rest for a while to minimize the effects of hearing fatigue. Take notes at every step of each test, use some charts, and write down as much detail as possible, such as speaker placement and setting parameters, so that when you feel that the sound is not as good as an hour ago, you can Then adjust back to the previous state. Remember, you have to deal with many variables here, and recording every parameter can make the adjustment process faster and more efficient.

Here are the specific steps:

1. Divide the floor of your entire listening room into a number of blocks of about 0.2 square meters (about 20 cm x 100 cm). Once these blocks are divided, your listening position can be tested in these blocks. If you are worried that this will leave a tape on the floor, you can choose tape that will not leave a mark.

2. Make a form and systematically record how you feel about listening to a subwoofer in each area. If you don't record this data, you can easily forget the feeling of listening in each area.

3. If possible, remove the seats in these listening blocks and place the two subwoofers in the center of the listening area, towards the center axis of the longest side of the listening room.

4. Adjust the gain of the two subwoofers down, and set their phase to 0°, set the equalizer on the decoder to “flat” position, and play the test music through the left, center and right channel speakers. Increase the gain of the two subwoofers until you hear them in the mix. Then turn the gain up a bit and then turn it down until you just hear the sound effects they appear. Don't worry, you'll have to make a final fine-tuning later: all you have to do now is to get a reasonable, useful playback volume from the subwoofer. Once this volume is set, turn off all channels. At this time, we assume that the crossover point of the subwoofer is set to 80Hz or nearby position.

5. Set your CD or DVD player to loop playback, then listen to each block and record your hearing experience.

You will immediately notice that in some blocks, the balance of sound is much better than in other blocks. Record it in your form. Once you have tried it in every block, go to the front and move the subwoofer farther away from the wall along the axis you have chosen. Then listen to each location in the listening room, record the feelings in each block, and note in which blocks the sounds sound particularly good or bad. It won't take long for the sound block to sound good and bad mode will come out. Repeat the above process until you are satisfied with the sound of the subwoofer. Finally, make a note of the best listening blocks for each subwoofer. From the table you recorded, you will find the best position for the subwoofer.

6. After finding the block with the best sound in the listening room, move the subwoofer to some position and take another listening test. This time, go to the block in the original listening area, and you will find that moving the seat position will improve the sound of the subwoofer in the listening area. If you are unable to move the seat by a wall or other object, you can skip this step.

7. Once you have found the “best effect” location for the subwoofer and listening position, turn all the channels on and adjust the gain of the subwoofer. Remove the tape paper.

Fourth, the adjustment of the crossover point

8. The 80Hz low-pass filter crossover frequency mentioned in step 4 is the best crossover point for your audio system. But if you need to adjust it or be interested in adjusting the crossover point, here are some quick ways to find new crossover points. In order to accomplish this task, you need to run both the main speaker and the subwoofer. If you plan to set the main speakers to "large" mode, set them to this mode.

You sit in the listening position and let an assistant adjust the low-pass frequency of the decoder's subwoofer down until you hear the sound of the subwoofer and the main speaker clearly separated. Then let your assistant adjust the low-pass frequency of the subwoofer up until you feel the sound of the subwoofer and the main speaker blend perfectly, achieving a smooth transition.

I have successfully completed the above steps using music and pink noise signals. Once you have set the crossover point and the sound is best, move to another seat and repeat the process. This way you will eventually find the best crossover frequency for a comprehensive sound. When you enter the equilibrium phase, you will find it necessary to adjust the crossover point.

Fifth, phase / delay adjustment

9. You may find that adjusting the phase setting (usually adjusted on the subwoofer and adjusting it on the decoder if necessary) will make the overall sound of the main speaker/subwoofer more balanced. The test immediately shows if there is an improvement: you may hear more or less low frequencies on one phase. Changing the phase will have both positive and negative effects on the acoustics of the listening room, so that the sound you hear at the listening position will be different. To make phase adjustments, you must be aware that doing so will have a mixed effect. As you said before, listen to the different parts of the listening area, let your assistant adjust the phase of one subwoofer (turn the other off) and listen to it until you get the best sound. Then do the same test on the other subwoofer, then turn off the first speaker. Finally, turn on both subwoofers and make more adjustments if necessary. You will find that this process is more helpful with different test software.

Although the delay adjustment is for different purposes, I still put it together with the phase adjustment, because when you adjust the delay parameters, you also change the phase. The delay can be seen as an electronic method of systematically placing a subwoofer or reducing the difference in signal transmission paths between subwoofers. Delay adjustments can be made with different goals, which are often used in professional audio and home audio. Some people find it easier to ignore the phase settings and put their energy on the delay. In the integration of the subwoofer sound effects, the delay can be used to bring the direct sound from the subwoofer and main speakers to the listening position at the same time. Knowing the speed of the sound, you can quickly calculate the difference in signal transmission distances in a variety of placement modes (so you calculate the delay), but how do you calculate the number of delays in Figure 39a? In certain cases, it is assumed that the front subwoofer and the left, center, and right speakers are placed in such a way that their sound reaches the listening position at the same time. Calculates the time (in ms) or distance (in feet or meters) that the sound is transmitted from the left, center, right, and front subwoofer to the listening position. Then calculate the delay of the rear subwoofer.

For example, suppose your left, right, and center main speakers/front subwoofer are 5 meters away from the listening position, while the rear subwoofer is 1 meter away from the listening position, then 5m–1m=4m. So you need to delay the rear subwoofer with 4m. In this way, the sound from the main left, right, center/front subwoofer and rear subwoofer can simultaneously reach the listening position.

Sixth, the balance setting

10. Balance. Be especially careful when making this adjustment: it produces as many sound problems as there are problems, especially when it's wrong. Some decoders do a good job, but others do a terrible job. Be aware of its limitations, and remember that it balances the direct sound of the subwoofer instead of your listening room! There are a few things to keep in mind before you start. An equalizer is an electronic device that adjusts the frequency and does not correct acoustic problems in terms of time. No analog equalizer can equalize a particularly steep curve in the frequency response curve, so you can only focus on making the frequency response curve flat or reducing the peak. Over the years, I have seen a variety of techniques for setting up an equalizer without using test equipment. Here's one of the most effective methods, assuming you're using a parametric equalizer. This equalizer is the best device for fine-tuning the subwoofer, which adjusts the gain, bandwidth and frequency of the subwoofer. Together, you can effectively adjust the low frequency spectrum. Welcome to the home theater network shopping guide network!

Having said that, you have done a lot of work to effectively improve the integration of the subwoofer with your sound system. You already know a little about the listening room space. When your equalizer's equalizer is set to 0, play your test software and hear if there are any peaks in the frequency response. If necessary, you can do this test in every seat in the listening area.

We must first have to pay more for the audible resonance. Set both the main speaker and the subwoofer to the on state. Select a correct band point and adjust an appropriate gain value, such as +3 to +4 dB and a higher equalization value Q. Then slowly increase it and then lower the frequency. You have to find the most obvious frequency point of the gain, you may need to do it several times. Once the maximum frequency gain effect is found, you find the resonant frequency. Slowly reduce the gain of that frequency until the peak disappears and replace it with a balanced and neutral sound. Now change the equilibrium Q value until the sound you hear is more balanced and natural. Adjust the gain value if necessary. Repeat the above procedure for other slightly lower amplitude resonant frequencies until you are satisfied. Now listen to each seat in the listening area.

The purpose of this is to find a compromised position of the acceptable frequency response you hear in all the seats in the listening area. This may not be possible at all. Instead, you may only find one seat in the listening area to achieve acceptable sound. But by following this method, you can find the placement and parameter settings for the best performance of the subwoofer. More home theater installation and debugging knowledge, welcome to enter the "home theater 100,000 why" channel.

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