8 Tips to Improve Your Sound Playback Quality
It is well known that the acoustics of a listening room have a far greater impact on the reproduction quality of an audio system than any other component. While there are many methods to improve acoustics, over-treating the listening room can be counterproductive. For example, having some diffusion is good; diffusion scatters sound in all directions and helps avoid echoes. However, making every surface in the room diffusive can worsen stereo imaging, as sound propagates in all directions and cannot be precisely focused into an image.
The acoustic situation in small rooms is even more complex. Although many audio publications cover this topic, they often lack definitive and pertinent advice. The problem lies in numerous contradictions, and different experts offer different opinions. However, there is consensus on the significant impact of the room's acoustic environment, speaker placement, and listening position on sound reproduction. This article won't delve into esoteric principles or bizarre acoustic treatment methods. We will only introduce some simple, practical, and achievable methods for treating the listening environment.
1. Lay a thick, dense carpet on the floor.
The floor is likely the most reflective surface for sound waves. While carpeting doesn't do much for low frequencies, the first thing to do is absorb some high-frequency reflections. Early reflections arriving within 5 milliseconds (ms) or slightly later after the direct sound become part of the direct sound and are perceived because they mostly come from the same direction. We should avoid letting pure-sounding speakers become muddled with high-frequency reflections bouncing off the floor. Since it's impractical to add soft padding to the ceiling, if the floor isn't carpeted, we have two parallel, highly reflective surfaces. Sound waves will reflect back and forth between the floor and ceiling, making the sound unpleasant.
2. Hang curtains on the windows.
Reflective glass is avoided in concert halls. In a listening room, because the walls are close, reflections from glass can easily become annoying. Consider installing curtains that can be drawn open on the windows; draw them closed when listening to music. Also, avoid placing bookshelves or furniture with glass front panels in the listening room.
3. Disrupt reflections from parallel walls.
Like the floor and ceiling, parallel walls can produce endless reflections, leading to "multiple echoes" and unpleasant sound. Try clapping your hands forcefully; if you hear an echo, it indicates a problem in your listening room. Bookshelves, especially those with books arranged randomly, act as sound diffusers and can break up reflections from these parallel surfaces. While specialized diffusion panels are available, placing a few bookshelves in the listening room can be quite effective.
4. Stick some foam at the "mirror reflection points" of the tweeter.
Unless your ceiling is as high as a church, you should stick some foam blocks at the "mirror reflection point" for each tweeter in your speakers. The "mirror reflection point" is the point on the ceiling (or floor) where, if you place a mirror, you can see the tweeter from your listening position. While ceiling treatment isn't as critical as floor treatment, doing it appropriately is still beneficial. Comparing Figures 1 and 2 shows that sticking foam just a few millimeters thick and no larger than 0.1m² at the ceiling's mirror reflection point significantly improves the room's listening environment.
5. Don't let reverb be too long.
Sticking small foam blocks at the mirror points won't drastically change the room. However, sticking large foam blocks or hanging very thick curtains will absorb too much sound, making the reproduced music sound lifeless. Thin, lightweight absorption materials absorb high frequencies well but have little effect on low frequencies. Typically, absorption material needs to be about half the wavelength of the sound wave to be effective. For a 10kHz sound wave, the wavelength is only 3.4cm, so foam a few centimeters thick can absorb highs. However, for a 200Hz low frequency, the wavelength is as large as 1.7m, so foam a few centimeters thick naturally has little effect. Consequently, the room will clearly suffer from tonal imbalance. What you hear will mostly be a reverberant sound field, with highs absorbed more and lows less, leading to a sound that lacks vitality and power.
6. Try listening slightly closer to the speakers.
Sometimes, experimenting by sitting a bit closer to the speakers can be worthwhile. In fact, many people often sit too far away, effectively listening to the room rather than the speakers. Listening closer can be more enjoyable. Although it might not sound as pure as the sound coming directly from the speakers, it serves as a useful reference standard for comparison. Incidentally, almost all recordings are made in the "near field" during production, regardless of the recording quality.
7. Floor reflections are a major source of coloration.
As mentioned earlier, absorption materials can absorb the high-frequency portion of early reflections from the floor and ceiling. The early reflections referred to here are those arriving within the first 5ms after the direct sound. Reflections arriving this quickly blend with the direct sound. The top two octaves of these early reflections might only produce some harshness, but their midrange frequencies cause coloration. Figures 3 and 4 show the situation with floor reflections present and after basic room treatment to eliminate them.
After eliminating reflections, the midrange becomes very ideal, with a smooth response. This is why line-source speakers can be confusing for some buyers. Because there are no delayed floor reflections (or more accurately, the combination of floor, ceiling, and speaker no longer produces reflections), the speaker's coloration is naturally reduced. However, for point-source speakers, it's still possible to find models with low coloration, as shown in Figure 5. The problem is, to achieve such good characteristics, you might have to lay large foam blocks on the floor. Of course, you can place them temporarily when listening and remove them later. Placing dense foam only at the mirror reflection points can solve the problem.
Sidewall reflections, however, are another matter. To add some sense of "space," some people prefer having some sidewall reflections. Because concert halls are large and spacious, sidewall reflections arrive after a certain time delay, making them pleasant to the ear. But in a home listening room, sidewall reflections arrive too quickly and don't sound as good. Trying absorption material at the mirror points and placing bookshelves near the sidewalls to diffuse sound has been attempted. Ultimately, determining the best approach requires practical experimentation. Note that if you want to use stronger sidewall reflections to enhance spatial sense, you need to specifically choose speakers with excellent off-axis response.
8. Experiment repeatedly with speaker placement for optimal bass.
Speaker placement is a complex issue; we can only provide a brief introduction here. Two main factors influence speaker placement: room resonance modes and the loading effect of the room boundaries on the speaker's radiation impedance. According to Allison's effect, when a boundary is at a distance of one-ninth of a wavelength from the driver, the driver isn't loaded by reflections from that boundary. Therefore, the speaker's sound radiation power at that frequency is reduced.
While computers and specialized software can determine optimal speaker and listener positions, spending a few hours experimenting with placement is highly recommended. Remember that the distances from the woofer to the floor, sidewalls, and rear wall should ideally be as different as possible. A general placement principle is that the square of the middle value of these distances should roughly equal the product of the maximum and minimum distances. Placing speakers closer to room corners will boost the bass.
You can test using a "warble tone" and a sound pressure level meter. If you hear more sound below 300Hz when the speaker is in a certain position, it indicates good placement. If you have access to an RTA spectrum analyzer, it makes determining speaker placement easier. Be patient with speaker placement; don't get discouraged by repeated trials. Hard work will yield surprisingly good results. Refer to Figure 5; as long as the original speakers are good, persistent trial and error will reveal that your audio system is truly excellent.
The acoustic situation in small rooms is even more complex. Although many audio publications cover this topic, they often lack definitive and pertinent advice. The problem lies in numerous contradictions, and different experts offer different opinions. However, there is consensus on the significant impact of the room's acoustic environment, speaker placement, and listening position on sound reproduction. This article won't delve into esoteric principles or bizarre acoustic treatment methods. We will only introduce some simple, practical, and achievable methods for treating the listening environment.
1. Lay a thick, dense carpet on the floor.
The floor is likely the most reflective surface for sound waves. While carpeting doesn't do much for low frequencies, the first thing to do is absorb some high-frequency reflections. Early reflections arriving within 5 milliseconds (ms) or slightly later after the direct sound become part of the direct sound and are perceived because they mostly come from the same direction. We should avoid letting pure-sounding speakers become muddled with high-frequency reflections bouncing off the floor. Since it's impractical to add soft padding to the ceiling, if the floor isn't carpeted, we have two parallel, highly reflective surfaces. Sound waves will reflect back and forth between the floor and ceiling, making the sound unpleasant.
2. Hang curtains on the windows.
Reflective glass is avoided in concert halls. In a listening room, because the walls are close, reflections from glass can easily become annoying. Consider installing curtains that can be drawn open on the windows; draw them closed when listening to music. Also, avoid placing bookshelves or furniture with glass front panels in the listening room.
3. Disrupt reflections from parallel walls.
Like the floor and ceiling, parallel walls can produce endless reflections, leading to "multiple echoes" and unpleasant sound. Try clapping your hands forcefully; if you hear an echo, it indicates a problem in your listening room. Bookshelves, especially those with books arranged randomly, act as sound diffusers and can break up reflections from these parallel surfaces. While specialized diffusion panels are available, placing a few bookshelves in the listening room can be quite effective.
4. Stick some foam at the "mirror reflection points" of the tweeter.
Unless your ceiling is as high as a church, you should stick some foam blocks at the "mirror reflection point" for each tweeter in your speakers. The "mirror reflection point" is the point on the ceiling (or floor) where, if you place a mirror, you can see the tweeter from your listening position. While ceiling treatment isn't as critical as floor treatment, doing it appropriately is still beneficial. Comparing Figures 1 and 2 shows that sticking foam just a few millimeters thick and no larger than 0.1m² at the ceiling's mirror reflection point significantly improves the room's listening environment.
5. Don't let reverb be too long.
Sticking small foam blocks at the mirror points won't drastically change the room. However, sticking large foam blocks or hanging very thick curtains will absorb too much sound, making the reproduced music sound lifeless. Thin, lightweight absorption materials absorb high frequencies well but have little effect on low frequencies. Typically, absorption material needs to be about half the wavelength of the sound wave to be effective. For a 10kHz sound wave, the wavelength is only 3.4cm, so foam a few centimeters thick can absorb highs. However, for a 200Hz low frequency, the wavelength is as large as 1.7m, so foam a few centimeters thick naturally has little effect. Consequently, the room will clearly suffer from tonal imbalance. What you hear will mostly be a reverberant sound field, with highs absorbed more and lows less, leading to a sound that lacks vitality and power.
6. Try listening slightly closer to the speakers.
Sometimes, experimenting by sitting a bit closer to the speakers can be worthwhile. In fact, many people often sit too far away, effectively listening to the room rather than the speakers. Listening closer can be more enjoyable. Although it might not sound as pure as the sound coming directly from the speakers, it serves as a useful reference standard for comparison. Incidentally, almost all recordings are made in the "near field" during production, regardless of the recording quality.
7. Floor reflections are a major source of coloration.
As mentioned earlier, absorption materials can absorb the high-frequency portion of early reflections from the floor and ceiling. The early reflections referred to here are those arriving within the first 5ms after the direct sound. Reflections arriving this quickly blend with the direct sound. The top two octaves of these early reflections might only produce some harshness, but their midrange frequencies cause coloration. Figures 3 and 4 show the situation with floor reflections present and after basic room treatment to eliminate them.
After eliminating reflections, the midrange becomes very ideal, with a smooth response. This is why line-source speakers can be confusing for some buyers. Because there are no delayed floor reflections (or more accurately, the combination of floor, ceiling, and speaker no longer produces reflections), the speaker's coloration is naturally reduced. However, for point-source speakers, it's still possible to find models with low coloration, as shown in Figure 5. The problem is, to achieve such good characteristics, you might have to lay large foam blocks on the floor. Of course, you can place them temporarily when listening and remove them later. Placing dense foam only at the mirror reflection points can solve the problem.
Sidewall reflections, however, are another matter. To add some sense of "space," some people prefer having some sidewall reflections. Because concert halls are large and spacious, sidewall reflections arrive after a certain time delay, making them pleasant to the ear. But in a home listening room, sidewall reflections arrive too quickly and don't sound as good. Trying absorption material at the mirror points and placing bookshelves near the sidewalls to diffuse sound has been attempted. Ultimately, determining the best approach requires practical experimentation. Note that if you want to use stronger sidewall reflections to enhance spatial sense, you need to specifically choose speakers with excellent off-axis response.
8. Experiment repeatedly with speaker placement for optimal bass.
Speaker placement is a complex issue; we can only provide a brief introduction here. Two main factors influence speaker placement: room resonance modes and the loading effect of the room boundaries on the speaker's radiation impedance. According to Allison's effect, when a boundary is at a distance of one-ninth of a wavelength from the driver, the driver isn't loaded by reflections from that boundary. Therefore, the speaker's sound radiation power at that frequency is reduced.
While computers and specialized software can determine optimal speaker and listener positions, spending a few hours experimenting with placement is highly recommended. Remember that the distances from the woofer to the floor, sidewalls, and rear wall should ideally be as different as possible. A general placement principle is that the square of the middle value of these distances should roughly equal the product of the maximum and minimum distances. Placing speakers closer to room corners will boost the bass.
You can test using a "warble tone" and a sound pressure level meter. If you hear more sound below 300Hz when the speaker is in a certain position, it indicates good placement. If you have access to an RTA spectrum analyzer, it makes determining speaker placement easier. Be patient with speaker placement; don't get discouraged by repeated trials. Hard work will yield surprisingly good results. Refer to Figure 5; as long as the original speakers are good, persistent trial and error will reveal that your audio system is truly excellent.