Ok I found a very interesting, White Paper Study done from,
The Science of Audio ...This is the conclusion after many pages and graphs of reading

One subwoofer at each wall midpoint is the best in terms of
Std, Max-ave and Max-min but does not support low
frequencies particularly well. Two subwoofers, at opposing
wall midpoints, performs very nearly as well as four at the
midpoints and gives a much better LF factor. One
subwoofer in each corner also has good low frequency
support, but does not perform quite as well as one
subwoofer at each wall midpoint, in terms of Std, Max-ave
and Max-min. If cost and aesthetics are considered,
subwoofers at 2 wall midpoints is preferred.

I've never heard it anywhere that a 4 sub setup somehow loses low frequencies. Not saying that you are wrong, but can you share your source?

I do know that some people complain that "I moved my sub out of my corner and put it on the middle of one of my walls right next to my seats, and there is less bass." Of course, there are lots of issues with that example. Corners make the bass seems louder and boomier, the sub placement impacts peaks (and nulls), so on and so forth.

Increasing from 1 sub to anything more than 1 sub helps to even out the whole low end frequency response. Maybe there are other factors playing into your example of 4 subs along the 4 wall mid-points (which to many experts is considered to be optimal for low frequency response) where low end is lost. Maybe it is just that enough of the nasty peaks (and nulls) have been lost that you are hearing less bass at certain frequencies and perceiving it as bad, when in fact it is just putting the bass at levels that they are supposed to be at?

Again, your source info would be great.

Oh, and I am by no means saying that you are wrong, just that this portion with 4 subs conflicts with what the general consensus among experts say.

Now, I will agree with you for sure that the difference in going from one sub, to 2 subs (even if not put into the ideal locations at the mid-points of opposite walls) yields the best "bang for your subwoofer buck" in taming the peaks and nulls and going beyond 2 definitely yields diminished returns for the price. It certainly does get better, but costs twice as much to get the last "20%" so to speak.

Here is a link to a YouTube video with Ian Colquhoun...

Multiple Subs

Ian published this video. i don't think any of his graphs showed a drop off in the low end.?

http://youtu.be/ayOXz26qm3I

Isn't that the same video I posted? Why yes, yes it is.

I don't think I can ever have enough subs Wife doesn't see it that way unfortunately.

I like Ian. He's a cool guy.

"One subwoofer at each wall midpoint is the best in terms of Std, Max-ave and Max-min but does not support low frequencies particularly well. Two subwoofers, at opposing wall midpoints, performs very nearly as well as four at the midpoints and gives a much better LF factor. One subwoofer in each corner also has good low frequency support, but does not perform quite as well as one subwoofer at each wall midpoint, in terms of Std, Max-ave and Max-min. If cost and aesthetics are considered, subwoofers at 2 wall midpoints is preferred."

The above is an excerpt from the conclusion of a presentation by Harmon I found online, which is based on a very nice Matlab simulation run in a rectangular room. Link: http://www.harman.com/EN-US/OurCompany/Innovation/Documents/White%20Papers/multsubs.pdf
I think that this is either the paper that the original poster is referring to or what they are basing their statement on.


Again, all of what is being said depends on having a sealed rectangular room with good dimensions, ie one wall dimension not a multiple of the other, etc. What I got out of reading the above is that it comes down to either 2 or 4 being the "best". By "best" they mean minimizing the seat to seat variation, for a number of seats, being the biggest factor. The next factor of importance being increasing output as the number of subs increases and the third being cost. If you are going to use 4, then it is best to put each one in a separate corner in the room. This will give you more output than having one or two. Having 4 subs at the midpoints of each wall will have less output than just having one subwoofer, which is not a good use of all of the added expense, though the seat to seat variation is a slight bit better. With 2 subwoofers at the midpoints of opposing walls you get nearly the same seat to seat variation, with half the cost, but slightly less output compared to 4 subs in separate corners. In the link above we see that Harmon ran simulations with two subs in both midpoint of opposite wall positions as well as 1/4 distance from the corner on same wall and the midpoint position was better with seat to seat variation. Though I saw a review of 2 Powersound XS30s (very nice looking subs by the way, which I would love to have in the future if I can fit in the budget), where the 1/4 distance along the same wall had slightly better seat to seat variation in a room of different size dimensions than Harmon used in the simulations. Link: http://www.hometheatershack.com/forums/h...mpressions.html

To sum up, 2 subs seems to be basically the best in terms of value, seat to seat variation and additional output compared to using one sub. Having 4 subs may produce either additional output or better seat to seat variation, but maybe not both. Hopefully the room that the subs would go into would be a rectangular and sealed, then the best position will either be the midpoint of two opposing walls or 1/4 distance along one wall.

Interesting. So much in there that seems to go hand-in-hand with other resources, and a bunch that doesn't. Typical corner placement creates exagerated (boomy) bass. Of course their test room was an almost bare 20'x24'x9' which isn't acoustically great. They tested directly in the center of the room, which is "less-than-ideal" as nulls are easily occuring there, so on and so forth.

So what does that mean? Heck, I don't know. Too many variables and how it does or does not simulate what you have in your house for room size, relationship of seating (exact center of the room for example), what is in your room impacting acoustics, etc.

I guess I look at this somewhat "real world test" is that someone could do the exact same test in a different room and get different results. That is why these kinds of tests should be done in such a fashion that tried to eliminate the specific room impact. Much like how Axiom uses an anechoic chamber to measure the speaker and only the speaker without coloration of the listening space. Again, if all real-world listening spaces were the same, then cool, but since they aren't then I say that the test is somewhat flawed. Good information for the most part, but still not a perfect test. I guess it is the perfect test if that room happens to be YOUR room...

Nick, Troy is apparently(as Nick B suggests)using the Harman study as the source. What's being misinterpreted in some of the comments here is the "LF factor". This doesn't mean that the total low frequency energy goes down when more subs are in operation. The total actually increases, but a correction factor to "normalize" for the number of subs is applied to get the LF factor. This measures the efficiency of adding more subs in a particular configuration. In other words, each added sub doesn't increase the total low frequency output as much as would be thought simply by looking at the increase in numbers of subs.

The Science of Audio

yes Nick it is what I was talking about

well really one could say that 6 subs is better than 4 or hell 8 subs is better than four or six. one in each corner and one at each mid wall. heck really for this where do we stop. I only need so much volumn in the LF. where does it stop. looking at a price point and best LF if I were to buy 2 EP 500's at $2200 or four at $4400 or do I go to $10000 ?

I am pretty well sure that if I bought 4 EP500, I am not going to hear the difference with my ears in any room that is worthy of $6000 more

Ah. So you are saying that the lower end still increases, but just not as much as the rest of the range. I was reading it as though you were saying that it was actually decreasing...

No "rest of the range" consideration is involved. In some configurations the increase in total low frequency output isn't as much as would occur by simply increasing that output to correspond with the greater number of subs. For example, four subs at opposite wall midpoints certainly have more total low bass output than one in a corner, but the LF factor is lower.

Agreed, however with one single sub played louder, you might get an increase at certain spots in the room (more LF), but you will get deeper nulls in others.

More subs are meant not to increase the impact or perceived "volume," but to reduce the nulls (and also tame some of the peaks) across a wider listening space. That would, in effect, make some things seem quieter or that there is less LF output.

So I guess it comes down to super bass in a couple of sweet spots, or more normalized bass over a larger listening area.

Either can be considered "right" depending on the end goal.

Oh, my "rest of range" was in regards to the increase above 40Hz but still in the subwoofer's domain of sound reproduction (under 90Hz). I didn't mean the rest of all audible hearing. Check out the video I linked before and go to about 5:37 into it. It has the graph and Ian talks about how much less the gain is between 19Hz and 35/40Hz vs. the larger gain above 40Hz and under 90Hz. So if we only care about 1 sweet spot for a peak, and only want 19-40Hz reproduced well (based off of the Axiom tests in the video, individual rooms would differ), then we are all set with just 1 sub and to most that is perfect. Heck, I have had a 1 subwoofer setup for 18 years and loved it. I am only a month or so into my 2 subwoofer setup and I am finding that I am enjoying it even more. Not because I feel more of the really deep bass, but because my room's sweet spot was NOT where I liked to sit when watching a movie (my back row had better sound, but my front row is perfect for me for the immersive visuals). I've effectively expanded the sweet spot to include my seat and improved the overall under 100 Hz freq. response at the same time by improving the "above 40Hz" top half of what the subwoofer is producing for me.

Part of my limitation is that I couldn't do a subwoofer crawl, well not really anyway... I had to put my sub up front behind my false wall. That was the plan, and I could only move the sub right and left along that wall. Dead center would have put it behind the VP180 and between the two I would have lost about 6 feet of the room length to get them in the proper location with the proper spacing. I didn't want to give up more than 2.5' of depth, so that meant putting the sub between the center channel and one of the front mains (right or left).
So I am dealing with a less than ideal audio setup based on asthetics. Then again, we all are working with less than ideal spaces. To make a perfect room for audio would be pretty ugly, in my opinion, to accomplish for a home theater.

The biggest thing to get out of the article is that the biggest reason to get more subs is to have smaller seat to seat variation in frequency response from 80 Hz and down. It is relatively easy to set up one subwoofer so that one seat is great, as long as the sub is big enough for the room dimensions and we are talking about a rectangular sealed room. Just google search crawling for bass and you'll find several articles that go through the procedure. The difficulty comes when you would like to have that same good frequency response from 80Hz and down in each seat in a home theater setup with say 6 or 8 seats. The easiest way to do that is with either 2 or 4 subs AND seat to seat variation doesn't necessarily improve going with more than 4 subs. But the improvement in seat to seat variation with 4 subs is very similar to that of 2 well placed subs.

An added benefit of going with multiple subs is that you gain extra output in comparison to one sub, if they are placed well. Only people with enormous rooms would need to buy extra subs in order to get sufficient output at reasonable listening levels. After all, Axiom, Hsu, SVS, Rythmik all make subs that will be able to give good bass output in very large rooms.

It's not so much the output level; One EP500 set at 5:30 or 6:00 (v2) was enough to rattle pictures on the wall and make a closet door behave like someone was trying to get in (19' x 21' x 8'). It's about balancing out the nodes in the rest of the room - that's what the extra subs get you.

Exactly. My SVS was more than plenty for my 14'x24'x8' room. My "SVS Clone" just makes more seats sound good.

Thump in the Rump?

Nope, more "shake" in the rump (especially at 0:40 in):

Shake Your Rump!