Experience with stacked subwoofers?

@guysellingstuff Sadly, not yet. I'm still waiting on my third pair the dealer has out for repair. It turns out the company that makes the amp packs for the S/510 went out of business and/or stopped making them. REL has to do component level repairs now and have been backordered on parts. I keep hearing "any time now," but REL hasn't delivered yet. My wife and I are frustrated with it. We are anxious to get it all completed and dialed in.

The only other thing that remains for now is delivery of my 2nd HRS EXR rack. I don't expect that to be delivered before later this month.

@guysellingstuff I finally got my third pair of REL S/510. I installed them this afternoon, and started with some setting guidance recommended by my dealer's installer. I have a new HRS equipment rack coming within a couple weeks, so they will tune the six-pack when they deliver the rack. In the meantime I'm enjoying it so far.

It's interesting to see this, as it uses old "column speaker" tech to reduce vertical dispersion and increase horizontal dispersion.   You can see old Grateful Dead shows where they were using this technique to shorten throw and increase horizontal dispersion.  

The other technique is to line them up on the floor horizontally, an array, as this will reduce horizontal dispersion and focus bass more in the central area of the room.  Try it.

@lonemountain 

The other technique is to line them up on the floor horizontally, an array, as this will reduce horizontal dispersion and focus bass more in the central area of the room.  Try it.

That’s not how REL six-pack line arrays work. Each level has a different role and is configured differently (xover/gain). The height of the sub is part of that. There is no good reason to lay them out horizontally, and I have no space for that anyway.

You can read more about REL six-packs here: 
https://rel.net/blogs/line-arrays/rel-six-packs
https://rel.net/blogs/learn-and-explore/make-mine-a-six-pack

@dwette Have dual S/ 812s with Tannoy Kensingtons and considering a 2+2 stack. Adding the second REL was an astounding upgrade.  How did you find going from dual to a four stack?