speaker recommendations for a 12 x 12 room?

One problem of small rooms - especially small, square rooms - is the resulting large peaks and dips in the bass region due to speaker/room interaction.

If you can place the speakers with some assymmetry in the horizontal plane, relative to the room walls, that would probably be somewhat beneficial in the bass region. For example, instead of having your speaker-listener-speaker triangle nice and symmetrical within your 12-by-12 square, try rotating it either clockwise or counter-clockwise (as seen from above) by about 20 degrees. This will make the distances of each woofer to its nearby room boundaries different in both the lengthwise and widthwise dimensions. The purpose of this is to stagger each woofer's room-interaction peak-and-dip patterns in the bass region as much as is practical, as the resulting average (which is what your ears hear in the bass region) will be smoother.

The other problem presented by a small room is the relatively early onset of reflections. In general, reflections arriving earlier than 10 milliseconds after the first-arrival sound (corresponding to a path length difference of about 11 feet) are likely to be detrimental. Ten milliseconds isn't a hard cut-off threshold; it's more like the center of a fuzzy transition zone. Anyway, in my opinion fairly directional speakers may be your best bet in speaker type for this application, or at least speakers with a fairly smooth power response. Ideally, the speakers could be aimed such that the early sidewall reflection is off the opposite wall instead of the wall near the speaker (I can go into some detail about this if you'd like). Such directionality calls for large drivers, which means mini-monitors won't be ideal in this respect. In the interest of minimizing the audible effects of early reflections you might want to place diffusion or absorption in the early reflection zones, but in my opinion don't overdo the absorption or you'll end up with a lifeless-sounding room.

Duke
dealer/manufacturer

Bdgregory, glad to hear it worked for you!

Pryso, I've found diagonal setups like you describe to often work well with planars, like Maggies and Quads. Now a dipole does have a bit smoother in-room bass than a monopole, according to an AES paper by James M. Kates, so the symmetry of a true diagonal setup is probably okay. But with a monopole speaker, my suggestion would be to not go all the way to a true diagonal but somewhere in between, to get the low frequency sources asymmetrical (with respect to the walls) in the horizontal plane.

That's my theory, anyway.

Duke

Iplaynaked, I realize that using large-diameter woofers in a small room is counter-intuitive. But then much of audio is counter-intuitive. For example, my suggestion to rotate the speakers-plus-listener triangle by about 20 degrees (resulting in asymmetry relative to the room's walls) is counter-intuitive, but Bdgregory found it to be beneficial.

Some of the acoustic challenges presented by a small room can be addressed through good radiation pattern control without over-emphasizing the bass region; in fact, those are two different issues. Some speakers systems with good radiation pattern control would have too much bass for a small room, and some would not.

In my opinion two issues need to be addressed in the bass region. One is the room-induced peak-and-dip pattern, and the other is room gain. I mentioned introducing some asymmetry to help smooth out the peak-and-dip pattern; to address room gain, you do not want a "flat" speaker; you want one with a gently downward-sloping frequency response. Typically, a sealed box will do a better job of giving you such a gently downward-sloping response curve than a vented box will. But... not always. "Typical" room gain is a 3 dB per octave rise below 100 Hz or so. If properly designed and tuned, a vented box can have a response that is essentially the inverse of that 3 dB per octave rise - and this can rival or surpass a sealed box as far as natural-sounding bass goes (a 3 dB per octave downward slope is impractical if not impossible for a sealed box). I personally favor bass systems that are somewhat user-adjustable, as the low frequency acoustic environment varies enormously not only from room to room, but from place to place within a room.

If designed to do so, a rear-ported box can give unusually extended, natural-sounding bass even when placed in or near a corner. Audio Note designs their rear-ported speakers for corner placement, and while I do think their specs are somewhat optimistic their speakers sound quite good in the bass region when set up as recommended. It's a matter of designing and tuning the speaker for its anticipated environment.

Duke

Iplaynaked asked:

"Er, what specifically do you feel are "hard and fast rules" that are counter-intuitive, as you say? I believe everyone here would like to know, actually. I would."

Well, that's not really what I said. I said that much of audio is counter-intuitive.

Okay, I don't know if these facts are so widely accepted as to be considered "hard and fast rules", but I think they are counter-intuitive:

1. Total harmonic distortion figures fail to reliably predict subjective preference.

2. The perceived tonal balance of a loudspeaker can change with loudness level even if the measured frequency response curve stays the same (Fletcher-Munsen curve; this one might qualify as a "hard-and-fast rule").

3. The on-axis anechoic frequency response curve is not a reliable predictor of perceived sound quality or tonal balance.

4. The ear largely ignores reflections arriving later than .68 milliseconds after the first-arrival sound as far as directional cues goes, but takes into account these same reflections as far as tonal balance and loudness goes.

5. Semi-random distribution of multiple low frequency sources in a room results in smoother bass, both measured and perceived, than careful placement of a single low frequency source.

6. The ear perceives sound quality very differently from the way the eye judges a frequency response curve; narrow-band peaks and dips that leap out to the eye are often inaudible to the ear.

7. The ear has a characteristic called "masking" that tends to ignore a low-level signal in the presence of a louder signal if they are close in frequency. This principle is applied in audio data-compression algorithms.

8. This principle of masking works in the frequency domain but not in the time domain, so that if the low-level signal is a distortion that arrives later in time, perhaps because of a path lenth difference (as with diffraction), then it is much more likely to be audible.

9. Speaking of diffraction, this is a type of distortion that our ears have a level-dependent sensitivity to; that is, we don't hear it at low volume levels but we do at high volume levels (as a harshness) - and this is one of those distortions that is not revealed by a frequency response curve.

10. The ear is relatively insentitive to the preservation, or lack thereof, of the phase relationships in a music signal. I'm not saying it's undetectable, but certainly not as readily detectible by the ear as by a microphone.

I could go on, but ten seems like a reasonable number to stop at.

By the way, I am not advocating 20 degrees of rotation of the speaker/listener triangle as a "hard and fast rule". It is an application of a principle to a specific situation. I trust that a re-reading of my posts in this thread will reveal what that priciple is. Being able to apply principles is more useful than memorizing rules, because the "rule" may not be practical to apply in the next person's room, but perhaps the principle can be applied in another way.

Regarding what size drivers and what type of box a speaker should have in a small room, I think you are arguing based on generalities that apply to most speakers, and I'm saying that if done right the specifics of a more nearly ideal solution in this case are different from what an overview of generalities would predict.

Duke
dealer/manufacturer

Thank you very much, naked... but between you and me, I just talk a good game.

Cheers,

Duke