Two vs four subwoofers for music playback

Duke >> Also, it is not necessary that all four subs be identical.  In fact in his own distributed multi-sub system, only one of Earl Geddes' subs extends all the way down.  <<

Thanks for that information, Duke! In my setup, only one of three goes to 15 Hz, and it seems to be enough. Since that was only one example, I hesitate to recommend such an approach to others. But now with Geddes, N = 2, much better!

I went from two subs to three. I considered four, but in my case, in a dedicated room, I have full freedom of placement and also have measurement equipment to get them where overall frequency response (FR) is smoothest. So I thought I’d try three first, since we’re getting old and trying not to get a ton more STUFF. I like the result. I still might go to four someday.

The advantages of three over two are easy to hear and match what people say. First, smoother FR at the main listening position. Second, a greater sense of envelopment. Third, far smoother FR across space in the room. I can walk around the room while bass-heavy music is playing and not go from areas of little bass to areas of too much bass. The variation is much, much less.

Try to get all four subs the same. If not identical, than at least don’t mix ported and sealed subs.

I also highly recommend measuring (use REW or an OmniMic [simpler!]). You can then fine-tune location and phase relationships to get smoothest bass. It’s not an absolute necessity, but I for one like to have the objective measurement in hand as well as listening impressions, especially in the bass.

The use of woofer towers -- essentially stacked woofers -- will produce more output, but their usefulness at evening frequency response is debatable. The utility of a distributed bass array (DBA) comes from the distribution of woofers across distances that are significant fractions of a LF wavelength. Then ideally, one woofer’s node will be another woofer’s peak, and the response will be smoothed. It’s a kind of averaging.

That doesn’t happen by stacking woofers. It does happen by putting them in different parts of the room. Now, in stacking, the multiple woofer heights can help spread out floor-bounce cancellations, which is useful, but I would expect much more value to come from woofers distributed across space. A very tall woofer tower, I guess, could give some of that effect.

Every room is different, of course, and some will benefit more than others from DBAs. Some lucky listeners have rooms with exactly the right combination of bass retention and loss so that little or no special action is needed to get even frequency response.

@aldnorab - I have heard of their being used in either way (stereo or mono). In my system, I use the 3 in mono, because of equipment limitations. Also, it’s hard to run 3 of anything in stereo! I ran the 2 in stereo before that.

As to spaciousness, that’s an interesting question. I am not sure how much spaciousness in stereo subs is real (i.e., on the recording) and how much is caused by slight phase differences, which might create a sense of spaciousness. IMO, it’s one of those areas in audio where it’s difficult to know exactly what’s going on. If I had 4 identical subs, though, I think I’d try them in stereo. One reads that many modern recordings do have stereo bass, and it would be interesting to compare.