Speakers to alleviate room anomolies

Room effects dominate in the bass region, and the peak-and-dip pattern is a function of room dimensions (and damping), source location, and listener location. In other words, move the bass source(s) and/or the listener and you re-arrange the peak-and-dip pattern.

One solution is to have as many bass sources as is practical, and have them spread asymmetrically as far apart as is practical. This way each bass source interacts with the room differently, producing a unique peak-and-dip pattern at any given listening position, and the sum of these dissimilar peak-and-dip patterns will be smoother than any one of them no matter how optimally placed. And if you want smooth bass over a large listening area, this technique is more effective than equalization (it is arguably more effective than equalization for a single sweet-spot as well, based on comments from people who have tried both).

If I understand correctly, by adding the Velodyne you now have three bass sources in the room, so that might be the reason why it smoothed out the bass for you. If you keep the Velodyne and go with small speakers that don't contribute much in the bass region, you may well end up back where you started.

In my opinon the theoretical ideal is multiple subwoofers scattered around the room, and they can be fairly small. In this scenario the main speakers don't need to carry the deep bass, so they can be smaller... but for aesthetic reasons few people find it practical to go the multisub route.

Duke
dealer/manufacturer

Rleff, in general it's desirable to have a lot of low frequency sources in-room, as long as you aren't stressing the main speakers and as long as you aren't over-emphasizing some portion of the bass region or otherwise creating a problem (like your wife says you're sleeping on the couch). Of course in some cases it's more desirable to relieve the woofers in the mains of having to make long bass excursions, so the best answer depends on the specific situation.

Snook2, it doesn't matter how capable the main speakers are, the room's effect will dominate in the bass region. There are four approaches to smoothing the bass that you can use singly or in combination:

1. Speaker and/or listener re-positioning. By all means visit Jonathan Tinn's speaker placement page. If it's aesthetically acceptable, you might try an asymmetrical setup. Imagine looking down on the speaker-listener-speaker triangle within your rectangular room, and imagine rotating that triangle clockwise or counter-clockwise maybe 15 or 20 degrees. Don't go all the way to diagonal; that would again be symmetry, and asymmetry is usually your friend in the bass region.

2. Add low frequency damping in the form of bass traps. This works well at not only taming peaks but also at filling in dips. I don't think bass traps can eliminate an 8 dB dip, but they can make it shallower.

3. Equalization works well for a small listening area, but it's a two-edged sword if good sound in a wide range of listening locations is a high priority. You see, boosting a dip or notching out a peak in one location can result in boosting a peak and notching a dip in another. The better equalization systems use readings taken in a wide variety of microphone locations and then calculate the appropriate EQ curve. Global (room-wide) bass problems are good candidates for fixing with EQ, but in my opinion localized bass problems usually are not.

4. You can use multiple (imho preferrably asymmetrically placed) bass sources, which works for reasons I've described in my previous post. Credit to Earl Geddes for teaching me this approach. Note that multisubs reduces the variance from one listening location to another, so that any remaining problems are likely to be global and therefore are good candidates for fixing via equalization.

Bob Reynolds, what I meant by "peak and dip pattern" is the frequency response at a specific microphone or listener location, rather than the room-wide pattern. If we could look at a map that showed the frequency response throughout the room, that "peak and dip pattern" would indeed depend only on the source(s) and the room - not where ears or microphones are positioned within the room. My apologies for the ambiguous wording.

Duke