raising subwoofer off floor by 20 inches

All subs should be off the floor by approximately 27-31 inches. This idea is from ASC (the tube trap people). It works by minimizing standing waves as low frequencies and providing better coupling of the woofer drivers with the room. ASC makes a special tube trap to elevate your subs off the floor to take advantage of this idea.

I should note that the height off the floor and distance into the room can vary depending on ceiling height.

thanks guys for your comments!

i am actually quite content with my setup. the suggestion came up during a casual conversation with a velodyne dealer (i was trying to get a good deal on a second dd-12). so i figured why not ask my fellow audiogoners before i try out the placement.

Newbee, i am sending full signals from source to both main amps and subwoofer, which is set to respond to 60hz and below. the sliders are indeed equalizer adjustments made to achieve the somewhat flat response. my current goal would be to achieve similar or better results without adjusting so much of the equalizer settings.

thanks Hifidreams and Etbaby for your info. the asc subtrap is quite interesting.

>>All subs should be off the floor by approximately 27-31 inches<<

Really? On what empirical data is this based? Interesting that Velodyne, Vandersteen, Kharma, etc. don't recommend this, only ASC. I'm sure it has nothing to do with their special tube trap that elevates the sub.

Szutinglee, Have you tried moving your listing position and speakers a bit. Some times we locate them in a null or a node which results the the uneven response indicated by you equalizer settings. Some times not, its just the room dimensions. You might also get a smoother response just by moving the sub around as well.

Just for fun, you could put the sub on a chair or a small table and see if you notice any difference in the bass.