Experience with stacked subwoofers?

@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.

SCM7 

@emergingsoul 

An awful lot of old people still voice “you shouldn’t need subs” and I think this was accurate in the days of Led Zeppelin, early Genesis, English rock and roll.  What I see these bands doing with subs on the recording side has certainly ended that idea. Pop music (Ariana and Sabrina carpenter ) - Americana ( Sarah Jaroscz) even country (post Malone/Jelly Roll/ chris Stapleton, Kane Brown ) -are working the subs hard.
 

Brad