I have 2 sets of CSA 4’s on my Foundry subs. The subs are located on a wall opposite of the FR’30’s for now and I will be getting 2 additional F12’s in the near future. Locations are still a work in progress but an array surrounding the listening position rather than alongside the main speakers seem to work best.
Back to Stack. They work. In my never ending battle with room nodes they help to calm things down. Bass just seems more solid, less of the additional harmonics to carry on. Sustained organ notes or fast fingers on a double bass stay tight, no bloom or blubber. Admittedly, dialing in the right location, output, slope and delay of the sub can effect the sound of the sub as much as the Stack footers. But, for a reasonably priced add-on, it does the trick.
I have 3 F12’s and am considering the Stack CSA-4 for them based on your advice. The 77 lb. weight is right in the middle of their range. What size threads work for these?
Did you ever get 4 subs going? I found 3 were all that I needed to reduce most room modes, but four would allow a double bass array concept. Mine are on 18" ASC sub traps, which really assist in keeping the bass and modes under control. If you get another sub, try it near one of the front corners since your others are on the back wall. I was surprised how much it changes things.
I haven’t found a final location for the 4 F12’s as my system is currently out of commission. I can say that a swarm of subs is the trend, roughly 4 corner locations. I didn’t like a single pair between the FR30’s. I’m pretty sure 8mm bolts are the correct size for the subs.
I bought 3 CSA-4 sets for my F12 subs, but the M8-1.25 threads are in customs in Memphis. Currently using the flat plastic pieces to hold them under the subs.
My system vocals and mid-range tone improved, but I lost a lot of detail and clarity with the Auva 100’s. They smoothed out the drums way too much, vs the Stillpoints that I was comparing with, so I can’t hear much a difference in low bass with these SW feet now.
The drums on music by the Who sounded like Keith Moon was playing in the room with the Stillpoints, with very fast drum transients and crystal-clear cymbals. Now the whole system is more like FM radio and lost all the wow factor. I have been giving things time to settle but can’t really tell what the subs are doing with the new feet. May try different feet again under the FR-30’s.
I’m a little confused - are you using these for the F12 while waiting for the mounting screws?
Sorry for the confusion. The Stack SW feet are on 3 of the F12 subs with the plastic flat support discs, instead of screws, which are being shipped. The speaker Auva 100 also did not have long screws in the US in M8-1.25 and so they are sending me some 40mm from UK. These will be too short to tilt speakers to ear level. The std. screws are 30mm and you can’t put the FR-30’S feet covers on as too short without removing a nut. To do what straightwire does for ear level tilting i need to order maybe 50mm adapters from somewhere.
Ah. So the AUVA 100 as currently being used is what, for you, is smoothing out the sound too much? Is that with or without the F12s in play?
For me, with or without the subs. Note i have not tilted down to ear level as many recommended,so do not rely on my experience yet. Note the Stillpoints required NO tilting to ear level. The speakers must be level in all directions, so were about a foot above my ear sitting level for the mids and tweeter panels. I will also try Gaia Titan Theis. I got a set used to check out for minimal cost risk.
I’ll be interested in this further comparison!
I have the Auva SWs beneath a pair of REL S510s and basically they enable me to have the subs working in my room to their full effect. I live in a block of flats so neighbors all around and have suffered with Bass issues in my room. The Subs helped tame and alleviate some of that - but it was only when adding the Auva SWs that the resonance that had been shaking window frames and other related issues stopped fully. My bookshelf speakers the Alta Audio Alyssas go low in the bass region already and the AUVA 100s beneath my Studio Pro stands have again provided clarity and removed some of the bass ‘bloom’ for want of a better word that I had in my room, even before bringing the subs in. The subs provided additional dimension to the soundstage and the Auva SWs took this up a notch by deepening that soundstage back to front which is now very apparent in tracks that offer that effect - some great Queen tracks on SACD are perfect for this
So far, I am pleased with the Auva SWs under my three F12 PSA subs. I need to get the rest of the system adjusted but believe these are working well to keep the bass tight with good depth.
I use 3 ASC sub bass trap stands which contribute and a couple membrane bass traps in my dedicated stereo room, too.
This review update is a long time coming, but I just wanted to say how pleased I am with the SW feet replacing the sliders on my REL Carbon Special, but it was only after I corrected a dumbbutt mistake that I really heard the benefit.
TL,DR - make sure the SWs are installed so they exactly meet the height of the original footers. At least for RELs with a bottom passive, this turned out to be crucial (I know - “duh, of course it would be!” 
). When I originally installed the SWs I bottomed out the M4-0.75 bolts in both the feet and the threaded holes on the underside of the sub. That made for a solid, secure feeling connection, but it inadvertently lowered the height of the REL passive from the floor. Sure what I heard was good, in some ways better than the stock gliders, but it wasn’t until I recently came across again a discussion about how the REL height is tuned to work optimally with the passive, that I checked and saw how far off it was.
Now, the one problem is that the threaded bolts supplied by Stack, when bottomed out on the SW foot side, are just barely long enough to catch the first thread or two in the REL mounting holes, if attempting to match the original glider height (2.025”, in case anyone is interested). However, it is just enough so the locking nut on that side can be snugged up against the bottom panel of the REL. Still, I would like to see Stack supply a slightly longer bolt to get more “bite” into the REL cabinet. The alternative (which I don’t like) is backing the feet off from the other end so more on the REL side can be screwed into the cabinet.
The result? I frankly was shocked at how much better it got! More power, more articulation, more musical. REL isn’t kidding around when they say height is a critical design factor in their bottom outfitted subs. Lesson learned!
The most recent newsletter from Stack specifically addresses the proper use and benefits of their SW feet on REL subs. Worth a look.
My second set of Stack AUVA SWs just arrived for one of my REL Carbon Specials.
I previously obtained great results using them on a REL Carbon Limited that shares a few floor joists with my listening couch, where they eliminated floor borne vibration while maintaining bass weight and enhancing definition.
I’m having no such problems with the Carbon Special which sits well off to the left of my listening position, but I am curious as to what I might hear there when I install them tomorrow.
I have two more REL Carbon Specials stacked near the front right corner of my room, but their combined weight exceeds the weight limits of the beefiest CSAs currently offered. I need to ask Josh’s advice there, though I don’t relish the process of wrestling with those subs for a potential install there.
I can also echo Tony’s comments regarding the importance of maintaining the clearance height of REL’s passive radiators…
Thank you Tony. After reading your post, am going to order a set of Stack Audio Auva SW CSA 4’s for each of my Carbon Special subs
This will be the first time I will be using quality isolation products. Would ordering a set of Auva 100’s at the same time for my Aspen FR 10 speakers get the most benefit from these subwoofer isolators?
This is a link to the Stack Audio page talking about REL sub isolation:
Andy, did you notice the same issue regarding the limited seating depth of the REL side of the SW screws, to get the correct height?
I’m not sure I can answer that for anyone, Walt. I’m a “change only one thing at a time” type audiophile. Others are not. I do think the FR10 will benefit from AUVA feets (although I’m not sure if the AUVA 100 would be the correct size?). My own approach would be to do either the speakers or the subs first, get them dialed in, get a good feel for the change to your sound, and then move to whatever’s next. But that’s just me.
Thank you so much for your excellent advise, Tony. Am including two pics of my system and a room diagram to show what I am up against. Those REL Carbon Special subs shake my floor violently. You see them placed where they are as they cannot be near my amps, speakers, nor over my cold air return vent.
Am leaning towards ordering 8 Auva CSA4 SW isolators with m4-0.75 threads. Am thinking would be best at same time ordering 8 Auva 100 isolators with the m8 x 1.25 threads. Would have considered the Auva 70 isolators for my Aspen FR10 speakers, but I want the extra vibration protection from my two Carbon Special subwoofers. The difficulty lies in my wooden floor suspended over an unfinished basement.
Any advice would be greatly appreciated before I submit my order. Thank you.
Walt
As lovely as your listening space is, I am super impressed and inspired by your room schematic!
Yes, nicely done!
I’d advise contacting Josh Stephenson at STACK to discuss this setup, Walt. While I can see where it might make logical sense to think it might be best to go with the AUVA 100 to better “fight the problem” of the suspended floor plus the RELs, it would probably be better to find out if STACK agrees with this assessment. Not that the ‘100s will hurt anything, but it may not actually be the best treatment solution. Your room treatment looks carefully thought out - it’s not too dissimilar from mine, so given how carefully you’ve done this part, giving a shout out to Josh would be worth the effort.
Sometimes “more” may not be the best answer! 