Dual Subwoofer Placement

Apology in advance for getting all mathy, but its V/N where V is the variance and N is the number of subs. So if one sub measures +/- 6dB then 2 subs will be 6/2=3dB and 3 subs will be 6/3=2dB and so on. Main point being, once again, its demonstrably proven with measurements that more is smoother, ie, better.

http://www.gedlee.com/Papers/multiple%20subs.pdf

Its a bit nerdy but good solid facts like this together with informed impressions from users like Tim that convinced me to build my DBA. Finally in one fell swoop my system went from bass being the weakest aspect to probably the strongest. And for only $3k! Yeah, science!

To those asking about my setup, I will be setting up two Martin Logan 1100X subwoofers with a pair of Martin Logan ESL 9’s. I’m estimating my crossover will be around 60-80Hz. I have about 10’ from where the speakers and subwoofers will be placed to the listening position (longer if I measured at the actual angle from the placement to the seats). The room is approximately 30’ wide

Tim & millercarbon,

I envision adding another pair of Velodyne HGS-10s to the room.  To review, the stereo setup is comprised of a pair of KEF Reference 1s and a pair of HGS-15s crossed at 40 Hz 4th order by a SMS-1 bass manager that provides acoustic room correction.  The HT setup uses six KEF LS50s and a pair of HGS-10s crossed at 80 Hz 4th order by Bryston SP3 processor with correction by a second SMS-1.  Would it be preferable to use the subs 3 & 3 or 4 & 2?

db

Hello DB,

     Back at it again?  Good.  I'd suggest that as long as you have 4 subs active in your room (the 2 HGS-15 and 2  HGS-10), and they are properly positioned in a distributed bass array configuration, then you will certainly attain excellent bass performance for both music and HT throughout your entire room.  
     For best results, you should position each sub sequentially around the perimeter of your room using either mics and frequency spectrum analysis software tools or using the crawl method.  Both are very effective and you can always run your room correction processing afterward, to see if the bass, in your opinion, is even further improved or sounds better without it.  It's completely your choice how you distribute the 2 larger and 2 smaller subs throughout your room.  The essential factor is that  4 subs are launching bass soundwaves into the room from independent, and typically asymmetric, positions in the room.  This 4-sub distributed bass array (DBA) concept has been both scientifically and anecdotally proven to be tremendously effective in virtually any room and with any pair of main speakers.   
     If you utilize the crawl method of sub positioning, begin the search for the optimum position of sub#1 in the right front corner of your room, begin by positioning the 2 HGS-15s as sub#1 and #2 and continue to progress counter-clockwise around the perimeter of your room for positioning the 2 HGS-10s as sub#3 and #4, I believe this will result in both larger HGS-15s being optimally positioned along your front wall and the 2 smaller HGS-10s being optimally positioned elsewhere, likely in a well separated and distributed configuration.
     I located my 4 identical subs sequentially around my 23'x16'x8' room using the crawl method.  The optimum positioning turned out to be 2 along my front 16' wall, about 2' away from each corner, and 1 along each 23' side wall, toward the rear of the room and also with each about 2' away from each rear corner.  I'm thinking your 4 subs may be optimally positioned similarly, but likely not identically, in your room.
     I'm willing to continue to assist you, pm me if you'd like.

Later,
 Tim

Would it be preferable to use the subs 3 & 3 or 4 & 2?

You lost me. Do not understand why different setups. Sound is sound, and the best is the best, movies or music. What is 3&3? What is 4 & 2? Besides 6 I mean.