Agreed. And, corresponding with Josh is wise. I don’t have as good of a room setup as @Walt1 but I do have the FR10’s, REL, and a similar sized room. A while back, when I asked Josh for his recommendation for my speakers, he thought the AUVA 70’s would be the best fit. Also, the 100’s are substantially larger (fatter) than the 70’s and they may look a bit out of place under the FR10’s - if that even matters.
Thank you for your kind words and sound advice, Tony and Tom. I will begin an account with Stack Audio and give them a call when their hours are open tomorrow - and hopefully get to speak with Josh Stephenson.
He would also be able to show me the big picture in my listening environment. And maybe even discuss vibration control under my amps. Which will be changing into the PMG m400’s hopefully late next month.
@tony22 [quote=“tony22, post:16, topic:43883”]
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?
[/quote]
I did notice that. On both of my subs, I kind of split the difference between how far I screwed the footer side of the adapter in before locking it down with the knurled nut so that I could get slightly more threads into the REL before locking that down with the supplied wrench.
For anyone trying out the Stack AUVA SW footers, I found it helpful to use a thick rolled-up hand towel to protect the feet as I slowly flipped the dainty 86lb sub onto its new feet. In other words, I was trying to eliminate any side load on the footers as I turned the sub right side up.
Listening now…
If a call into Stack doesn’t work, Josh is usually very responsive to the company contact email site. I will be using the C3 pucks under the M800’s next week. They worked well under the BHK600’s, so I expect similar results. Say hello to Josh for me.
Will you use the C3s from the start or listen first with stock feet? If both I would be interested in how they compare.
I will probably just put the Stack feet under the M800’s and leave it at that. These new amps may require four hands to move around and I don’t think I will be able to easily try them with and without the specialized feet. They worked before, that’s good enough for me.
I’ll use the stock feet for now and likely get the Stack feet later. After hearing what the Auva 100s do for the FR30s trying the Stack feet seems low risk.
When talking to PSA I mentioned the lack of handles on the 800s and they said there are hand holds under the heat sinks. The heat sink edges are rounded so should not cut. But there is still the matter of 97 lbs.
Yes, the heat sinks are tapered underneath but the length of the unit may make it an awkward lift. They are10 lbs less than the 600’s, which I have managed, but we shall see. They shipped last Thursday on half pallets via truck freight. Should have any day.
Mine shipped the same day and are scheduled for delivery tomorrow. I have moved the 600s by dead lift holding from diagonally opposite corners. I don’t think I received the right genes from my ape ancestors to do this with the 800s.
Exchanged emails with Josh Stephenson and ordered the Stack SW isolators today. He advised to order their products a step at a time so I can appreciate each incremental change. Like Tony had suggested 
When I attach these isolators and move my subs to their most effective placement and dial them in, will then order the speaker isolators next. Josh said either the AUVA 70’s or the AUVA 100’s would be a good fit for my Aspen FR 10 speakers. He said some order both and return the set they not want to keep. By far these customers usually keep the AUVA 100’s.
Seems a no brainer to order both and keep the ones that sound best.
Thanks to everyone for all your great advice.
Walt
Let us know your impressions on the SW’s and later on the Auvas.
I asked AI about my overweight subs. One of the AI’s advice was that using 5 each sw csa6 is ok . The AI chat gpt advice was not to use the csa6’s , instead use 6 each sw csa5 and got specific as to exactly where to place the other 2 feet in order to get proper weight loading.
What are the other components in AI’s system, is the room treated, and what are the room dimensions. 
Good one. Doubly so since you headed them off at the pass with the emoji.
Update on adding the AUVA SW footers to the second of my four REL Carbon subs. Some of you might remember that I was struggling with floor-borne vibration from one of my subs that effectively turned the floor to the right of my listening position into a transducer, and that the Stack footers effectively eliminated this problem, while also improving speed and definition of the lower frequencies.
For whatever reason, that second Carbon Special did not really excite the floor around it but, by adding the Stack SWs, I noticed further gains in bass definition.
This leaves two more Carbon Specials which are stacked in the front right corner of my room (the other two are positioned to the sides of my listening position). After adding the Stack SWs to the first two subs, I obtained further gains in bass definition by slightly dialing back the level of these two subs.
At first I thought that I’d be stuck dealing with those two because the current offering of CSA inserts would not handle their almost 190lb combined weight. I just realized that I might be able to fasten eight AUVA SWs into the bottom sub to handle their combined mass. I’ll have to check with Josh, but it seems that’s how I might proceed…
@weedeewop The subs that I asked about is GR Research double trouble at 135 lbs without mount holes. I give AI’s all of my equipment as shown and listed under Everything Else/System/System Photo’s #9344. My room is not enclosed & it is big, but if I were to close the doors it would measure 20’4" x 18’9" x 9’. The room is treated with 6 bass traps, 4 mid diffuser panels, 6 high diffuser panels and 4 stillpoints aperture II and I have 2 absorbers that I might hang for cloud coverage. I am also going to add a 12x9 wool carpet. I use several different AI’s , but I mostly like the depth of reasoning that chat gpt gives.
It was intended to be a joke, regarding AI’s particulars specific to AI’s stereo system. Seriously, my opinion, AI is not worthy.
Received the Stack Audio AUVA SW CSA4 isolators for my two REL Carbon Special subs. Installation was easy. After placing each sub upside down on a soft comforter, I removed the two rails using a 3 mm hex key flat. These rails are 2” in height. This left four pairs of bolt holes. Used the outer hole of each pair for installation.
Screwed in the M4-0.75 part of the adapter into the sub and tightened using the supplied wrench. After placing the isolator on top of the M8-1.25 part of the adapter, I had less than the 2” height required.
After removing the adapter, raised the nut on the M8-1.25 part of the adapter so only 3 threads were showing. Screwed on the isolator and hand tightened it to this nut. Inserted the other end of the adapter into the subwoofer bolt hole and screwed it down until I had the required two inches in height. Spun the nut on the adapter down to the subwoofer and while holding the bolt, judiciously tightened it with the supplied wrench.
Had sent an email to Josh Stephenson of Stack Audio later and he verified that I had done this installation correctly and he would contact their research team about possibly extending the length of the adapter.
Used the rolled towel method that andynotadam had mentioned earlier in this thread to turn these subs upright to avoid rolling those heavy 85 lb brutes onto these isolators. Thanks for the tip!
My Carbon Special subs are connected to the speaker binding posts on my BHK 300 amps using REL’s generic, supplied 10m Speakon cables.
Have 18 hours of listening on these isolators. The improvement in my bass performance was major from the get go. Sounded even more natural after a few hours of break in. My impressions:
The downward facing 12” passive drivers on my REL Carbon Specials no longer shook my suspended wood living room floor over my unfinished basement as violently. The bass and lower midrange resolution is detailed and accurate.
The cohesiveness of my system took on a huge upgrade. This is particularly important to me as I want each sound coming from my speakers and subs to sound like it belongs – and gels together - across the musical spectrum.
My bass sound before the isolators had been bloated and smeared and each bass “hit” sounded really soft and lacked the proper impact. Now the bass slam and musical impact rock.
These isolators are a huge step in the right direction of my bass control. I was playing the HF&MS REL playlist on Tidal music. On the most demanding of bass music tracks, my vibration control still needs a lot of work.
An example is the track “Why So Serious” by Hans Zimmer and James Newton Howard. At least tracks like this are now listenable.
In my listening environment with my system with my ears, I consider these SW isolators to be a necessity for my sound quality. Thanks to Stack Audio for showing me how awesome my Carbon Special subs can be. These isolators are the perfect complement to these outstanding subs.
Walt
Really appreciate the detailed update! Enjoy the refined bass.
I may need to revisit my Rel Carbon Specials with the SW footers.
I too realized the adapters weren’t long enough to cover the Rel curved supports height.
I mentioned to Josh about this and he said he’d look into it but I don’t know whether anything ever happened, it sounds like it didn’t.
(I think he was to supply me with longer adapters.)
You provide a good detailed explanation of the process you used to install the footers so I’ll look at mine again and try copying your method.
I don’t think I’m just getting the same bass extension with the SW footers as I did with the Rel curved supports, close, but it feels a little less.
What I did was re-introduce the Audiophile Bass supports I had originally with Rel Curved supports. (I have my two subs sitting on these.)
I initially put the SW footers on and removed the Audiophile Bass supports so the subs were sitting on the wooden floor. There was definitely a reduction in the bass output.
So I re-introduced the Bass supports to increase the sub heights off the floor.
As above, it increased the bass but not to the original level.