Mixing subs?

I've always  wondered why people place stacks of subs in the listening room.  Don't get me wrong, I have two REL s/812 in my system and was playing with them just this morning.  But my question is this.  We spend so much time and money, trying to control the bass waves in the room, bass traps etc..  why would anyone put stacks of subs in play.  It's just counter intuitive?  Happy to learn something today. 

The low cost option if you're pleased with the sound would be to repair the sub.  If you're getting no output it very well might be a dead amp.  I had a class D amp croak in one of my SVS subs.  Replacing the amp was straightforward and not costly.  Might be worth pursuing.  Good luck and cheers.  

@bigtwin  I assume you are referring to height-wise stacking?

Sub drivers stacked up height wise can nullify height-wise room modes and add another level of bass uniformity.

You can either put one subwoofer on the floor and another one in the ceiling, (in-ceiling sub), lift one up.... or you can get models with multiple drivers like these which stack drivers 6 ft up. The latter might work for above purpose, but, you lose phase control on the driver at height, so it comes down to the same and placement of a 2nd sub. 

Stacking very expensive single driver subs all the way up can be a li’l....silly. There might be better ways to spend your cash.

For example, this one’s the 6-10 model from Tekton. It’s just one sub priced at $1500 with multiple stacked up drivers.

I’ve always  wondered why people place stacks of subs in the listening room.  Don’t get me wrong, I have two REL s/812 in my system and was playing with them just this morning.  But my question is this.  We spend so much time and money, trying to control the bass waves in the room, bass traps etc..  why would anyone put stacks of subs in play.  It’s just counter intuitive?  Happy to learn something today. 

@deep_333 Wow.  That looks like a lot of sub for the money.  

@bobbydd Manufacturer ratings: Your E112 -1.5dB@22 Hz / REL No.32 6dB@15Hz / Perlisten vented R212 small room filter -10dB@18Hz.

Garmin JL Audio, SVS and Rythmik Audio produce subwoofers that produce substantial extra low frequency. Adding a fourth subwoofer you'll enjoy the stunning benefit of a full room distributed bass array using minor asymmetrical corner placements.  

Because of their dramatic roll off the REL and Perlisten are sub-bass woofers. While they'll definitely add their limited low frequency, just not what you're used to. -6dB of 15Hz is barely audible and simply won't excite a rooms standing waves which is why they can be stacked up most anywhere in a room. 

When I purchased my two Velodyne DD-12 Plus I moved the older version DD-18 and my HT's Earthquake Nova 15 in the corner areas. I ran the Velodyne Auto EQ then balanced the gain on the Nova. The bass array literally eliminated all the rooms standing waves.  

Today I use just the two DD Plus positioned crawl determined room bass modes and no treatments leaving me with a single standing wave within unused corner of the room. Both the SVS and the Rythmik offer different but very useful equalization that may surprise you. All the best with your outcome.