Experience with stacked subwoofers?

Having experimented with different subs and arrangements in-room  I can say with some authority that the results you get may surprise you. And it can go either way. My experience supports the fact that if a single sub is good, then two is way better, and not stacked on top of each other in one corner. While that gives you more output, it won't help control room modes and give you even bass response thru the room. Separate the two subs and treat them like they are stereo because bass is not monophonic. It does not mean they have to mirror image in terms of positioning but try running them on either side of the screen or tv out from corner along the front wall assymetrically and run some measurements. Keep playing with positioning until you are happy with the results and then do some DSP on the remaining peaks and you should be in pretty good shape. That second sub will even out the response and give you 3 db more sub output, helping perhaps cut down on low freq distortion a bit. Well worthwhile expense to add the second sub. 

@emergingsoul 

Stacking subs is not a gimmick or a marketing ploy.  But its effectiveness does relate to your goal sad others have said.  One sub is nearly Omni in a room and expose standing waves everywhere.  Moving it often just moves the stadium g wave/ null location.  If it’s for home cinema, most of the sub output is sound effects so almost everything relates to the screen.  If it’s for music, distributed arrays can work better using multiple sources turned down at lower levels  especially in ATMOS/ immersive.  I think Duke has spoken about this extensively. 
brad

@lonemountain 

Standing wave problem is overrated and most rooms don’t have this problem.  Lower bass waves are very long and permeate throughout the room quite well.

Also if you have decent main speakers for two stereo listening you shouldn't really need to have a subwoofer.  Fully endorse subwoofer or two for home theater, you want tanks to rumble your entire house when they move across the screen

I'm with Brsd on this topic as it's settled science going back to work done back in the early half of the last century at Bell Labs. Very common in PA application,  not as common in 2 channel home applications. 

BTW Brad, I picked up some used SAM'S powered by a Benchmark stack.  Very pleased with the results.   I'll stop by the next time I'm in town.

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