"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.