It has more and more occurred to me that setting up a satisfying home audio system in a small room is subject to some different considerations than when one has a larger room to play with. Let’s consider dedicated audio rooms only. By small I’ll somewhat arbitrarily define such a room as one where the width and length are each 20 feet or less and the ceiling height is less than 10 feet. A “large” audio room would thus include one which is 22’ wide x 28’ long x 12’ high. Obviously if you are working with rooms on the order of a hotel ballroom, that’s a very large room.
My own dedicated audio room, at 13’ x 11’ x 8.5’, is definitely in the “small” category. Now, some folks will just say that if you have such a small room you’ll never be able to get great sound.
Why? One reason is that some people believe that the room’s smallest dimension must be at least 20’ long in order to fully support bass down into the 20s of Hz. But what about car audio--don’t auto interiors fully support deep bass? Of course they do. Small spaces actually support and sound better in the deep bass because deep bass is reproduced in such rooms in the pressure mode--it’s literally pressurizing the small volume of air in the room. The same goes for headphone listening where the volume of air is much smaller yet--that between the drivers and your ears as contained within the cups of the headphones.
And in very large ballrooms and concert halls bass is experienced as a travelling wave which is basically resonance free but supported by the room boundaries. Any resonances of such rooms are well below the audible range and thus really unimportant to what we hear.
Actually, large (as defined) audio rooms are typically the most difficult for bass reproduction since they are most always of such a size that they will be subject to a lot of bass resonances below 200 Hz or so, making for an uneven response over the entire bass range. Bass in such rooms can easily have the familiar and dreaded “resonant” sound, typically with a “thumpy” or “boomy” midbass resonance around 60 - 70 Hz because of the primary bass mode between the floor and ceiling. Such resonances must either be ignored or dealt with through careful construction with planned “favorable” dimensional ratios to spread out the bass resonances more evenly, speaker and listener placement, bass trapping, or electronic equalization, and sometimes all of these methods.
I know for a fact that my small room fully supports bass down to well below 20 Hz. I’ve measured every speaker I’ve had in this room with the OmniMic v2 system. The more bass capable of them (e.g., Harbeth M40.2, Gradient 1.4, AudioKinesis Swarm subwoofers, and now my Dutch & Dutch 8c) put out substantial bass down to as low as 10 Hz, with flat bass right down to 20 Hz. And that bottom octave sounds very satisfyingly room shaking. Even bass-capable vintage speakers like the AR-3a and KLH Model 12 in this room are quite capable of substantial bass output into the low 20s.
No, the problems with small-room audio are not, in my experience, with bass response. The real problems lie elsewhere.
The audio problems with small rooms can be summed up in a single two-word phrase: early reflections. In a small room, even one totally dedicated to home audio reproduction like mine, with careful acoustical room treatment it is impossible to get both the speakers and listener far enough away from the room surfaces to avoid hearing early reflections of the direct sound from room surfaces, furnishings, and the audio equipment itself. By “early” I mean that the reflected sound reaches your ears only a few milliseconds after the direct sound from the drivers.
Now a general rule of thumb is often quoted that as long as the path the reflected sound takes results in a delay of about 10 milliseconds, the reflections will not be bothersome. By bothersome, I mean that the reflections can artificially brighten the sound in the midrange and treble, add apparent distortion, add a glaze, brittleness, grunge, buzz, or other obnoxious coloration. Bothersome can also take the form of severe distortions of the reproduced space, reducing image stability and outright changing apparent instrumental placement on the soundstage, and wreaking general havoc with the soundstage, reducing every aspect of its dimensionality. Reflections, in other words, can create nasty-sounding, treble-heavy tonal balance and a one-dimensional left-right line of vaguely placed sonic images. A slap echo effect can also easily be overlaid on every sound reproduced.
Since one millisecond approximately translates to one foot of distance, the rule of thumb is that if the reflected path is 10 feet longer than the direct path, all should be well. This means that both the speakers and your listening position must be at least five feet from any room surface in order to make the reflective path to your ears 10 feet more than the direct sound. It doesn’t take long to figure out that this is difficult to achieve as to any room surfaces a small room. Even if I sit 55 inches from the drivers of my speakers (as I have in my typical near-field set-ups in this room), either the speakers or listening position must be closer than five feet from the wall behind since my length dimension is a mere 13 feet.
And, in fact, I don’t believe the rule of thumb is correct. In my judgment, the reflective path must be twice as long yet, more like 20 milliseconds or 20 feet in order for the reflections to be translated into pleasing reverberation or space around the instruments, rather than annoying tonal colorations and spatial distortions. Obviously this is not going to happen in a small audio room.
But even if you have a large dedicated audio room, you are not free and clear of the problem of reflections. Even if your large room’s reverberation is pleasing, do you want to hear a bit of reverberation around all sounds coming from your speakers even if such reverberation is not present in the recording? Shouldn’t radio announcers speaking from a small, acoustically padded studio sound that way, with no reverb at all around their voices? Shouldn’t closely miked (as in inches or less) voices or instruments be all direct sound and no reverb from the recording studio or your listening room?
My acid test for determining whether my listening room is adding any sort or echo or reverb to recorded sound is the Clap Track on the Sheffield/XLO Test & Burn-In CD. From your listening position, the Clap Track as heard through your speakers should sound EXACTLY like it does through headphones: a single sharp transient handclap with absolutely no preceding or trailing echo or reverb tail. If you think you have it sounding correct, turn it up, as loud as you ever listen to music, say 95 dB peaks and see if it still sounds the same. That’s the goal--the touchstone. You may be surprised at how difficult this simple test is to pass.
Okay, I will admit that those with large rooms may simply say, “So what? I like the bit of added reverb/space my listening room adds to reproduced music because most music is not recorded in such a way as to assume that the home listening room is not adding any “sweetening” space/reverb to what you hear. Fair enough; if you want to sweeten poor recordings a bit, that’s fine. Just be aware that this is what you are doing. It’s not like you can subtract this “sweetening” for the properly made recordings. You will always be adding that “second venue” effect from your listening room’s acoustics.
But for small room listeners, this isn’t really an option. Small room second venue effects are just plain-and-simple nasty sounding. There is no getting around it. And this is why some argue that small rooms just aren’t suitable for high-quality audio reproduction. They don’t want to eliminate enough of the small room second-venue reflections to unveil the recorded acoustics because the result is only fulfilling for the best recordings. There are so many recordings that are recorded without enough space/ambience that much of what one listens to is likely to sound at least a bit dry and lifeless in a small room acoustically treated to eliminate reflections.
I understand this dilemma, believe me, I do. But I’ve found that I soon get used to hearing the immediacy of overly dry recordings as a virtue, or at least not an impediment. And the virtues of well-made recordings are breathtaking in a small, well-treated room, more so than in a large one.
My own dedicated audio room, at 13’ x 11’ x 8.5’, is definitely in the “small” category. Now, some folks will just say that if you have such a small room you’ll never be able to get great sound.
Why? One reason is that some people believe that the room’s smallest dimension must be at least 20’ long in order to fully support bass down into the 20s of Hz. But what about car audio--don’t auto interiors fully support deep bass? Of course they do. Small spaces actually support and sound better in the deep bass because deep bass is reproduced in such rooms in the pressure mode--it’s literally pressurizing the small volume of air in the room. The same goes for headphone listening where the volume of air is much smaller yet--that between the drivers and your ears as contained within the cups of the headphones.
And in very large ballrooms and concert halls bass is experienced as a travelling wave which is basically resonance free but supported by the room boundaries. Any resonances of such rooms are well below the audible range and thus really unimportant to what we hear.
Actually, large (as defined) audio rooms are typically the most difficult for bass reproduction since they are most always of such a size that they will be subject to a lot of bass resonances below 200 Hz or so, making for an uneven response over the entire bass range. Bass in such rooms can easily have the familiar and dreaded “resonant” sound, typically with a “thumpy” or “boomy” midbass resonance around 60 - 70 Hz because of the primary bass mode between the floor and ceiling. Such resonances must either be ignored or dealt with through careful construction with planned “favorable” dimensional ratios to spread out the bass resonances more evenly, speaker and listener placement, bass trapping, or electronic equalization, and sometimes all of these methods.
I know for a fact that my small room fully supports bass down to well below 20 Hz. I’ve measured every speaker I’ve had in this room with the OmniMic v2 system. The more bass capable of them (e.g., Harbeth M40.2, Gradient 1.4, AudioKinesis Swarm subwoofers, and now my Dutch & Dutch 8c) put out substantial bass down to as low as 10 Hz, with flat bass right down to 20 Hz. And that bottom octave sounds very satisfyingly room shaking. Even bass-capable vintage speakers like the AR-3a and KLH Model 12 in this room are quite capable of substantial bass output into the low 20s.
No, the problems with small-room audio are not, in my experience, with bass response. The real problems lie elsewhere.
The audio problems with small rooms can be summed up in a single two-word phrase: early reflections. In a small room, even one totally dedicated to home audio reproduction like mine, with careful acoustical room treatment it is impossible to get both the speakers and listener far enough away from the room surfaces to avoid hearing early reflections of the direct sound from room surfaces, furnishings, and the audio equipment itself. By “early” I mean that the reflected sound reaches your ears only a few milliseconds after the direct sound from the drivers.
Now a general rule of thumb is often quoted that as long as the path the reflected sound takes results in a delay of about 10 milliseconds, the reflections will not be bothersome. By bothersome, I mean that the reflections can artificially brighten the sound in the midrange and treble, add apparent distortion, add a glaze, brittleness, grunge, buzz, or other obnoxious coloration. Bothersome can also take the form of severe distortions of the reproduced space, reducing image stability and outright changing apparent instrumental placement on the soundstage, and wreaking general havoc with the soundstage, reducing every aspect of its dimensionality. Reflections, in other words, can create nasty-sounding, treble-heavy tonal balance and a one-dimensional left-right line of vaguely placed sonic images. A slap echo effect can also easily be overlaid on every sound reproduced.
Since one millisecond approximately translates to one foot of distance, the rule of thumb is that if the reflected path is 10 feet longer than the direct path, all should be well. This means that both the speakers and your listening position must be at least five feet from any room surface in order to make the reflective path to your ears 10 feet more than the direct sound. It doesn’t take long to figure out that this is difficult to achieve as to any room surfaces a small room. Even if I sit 55 inches from the drivers of my speakers (as I have in my typical near-field set-ups in this room), either the speakers or listening position must be closer than five feet from the wall behind since my length dimension is a mere 13 feet.
And, in fact, I don’t believe the rule of thumb is correct. In my judgment, the reflective path must be twice as long yet, more like 20 milliseconds or 20 feet in order for the reflections to be translated into pleasing reverberation or space around the instruments, rather than annoying tonal colorations and spatial distortions. Obviously this is not going to happen in a small audio room.
But even if you have a large dedicated audio room, you are not free and clear of the problem of reflections. Even if your large room’s reverberation is pleasing, do you want to hear a bit of reverberation around all sounds coming from your speakers even if such reverberation is not present in the recording? Shouldn’t radio announcers speaking from a small, acoustically padded studio sound that way, with no reverb at all around their voices? Shouldn’t closely miked (as in inches or less) voices or instruments be all direct sound and no reverb from the recording studio or your listening room?
My acid test for determining whether my listening room is adding any sort or echo or reverb to recorded sound is the Clap Track on the Sheffield/XLO Test & Burn-In CD. From your listening position, the Clap Track as heard through your speakers should sound EXACTLY like it does through headphones: a single sharp transient handclap with absolutely no preceding or trailing echo or reverb tail. If you think you have it sounding correct, turn it up, as loud as you ever listen to music, say 95 dB peaks and see if it still sounds the same. That’s the goal--the touchstone. You may be surprised at how difficult this simple test is to pass.
Okay, I will admit that those with large rooms may simply say, “So what? I like the bit of added reverb/space my listening room adds to reproduced music because most music is not recorded in such a way as to assume that the home listening room is not adding any “sweetening” space/reverb to what you hear. Fair enough; if you want to sweeten poor recordings a bit, that’s fine. Just be aware that this is what you are doing. It’s not like you can subtract this “sweetening” for the properly made recordings. You will always be adding that “second venue” effect from your listening room’s acoustics.
But for small room listeners, this isn’t really an option. Small room second venue effects are just plain-and-simple nasty sounding. There is no getting around it. And this is why some argue that small rooms just aren’t suitable for high-quality audio reproduction. They don’t want to eliminate enough of the small room second-venue reflections to unveil the recorded acoustics because the result is only fulfilling for the best recordings. There are so many recordings that are recorded without enough space/ambience that much of what one listens to is likely to sound at least a bit dry and lifeless in a small room acoustically treated to eliminate reflections.
I understand this dilemma, believe me, I do. But I’ve found that I soon get used to hearing the immediacy of overly dry recordings as a virtue, or at least not an impediment. And the virtues of well-made recordings are breathtaking in a small, well-treated room, more so than in a large one.
