Rel Does Not Recomment Isolation Stands

Their advice is about the default, best. I don't know about springs.

But what I do know is that there can be cases when there are room modes which are located between ceiling and floor, and lifting a sub can address that. That would be an exception that I bet REL could accept.

From my own experience REL is in the right here. 

SVS, JL and the RELs S812 (I think) it's not ported are pretty serious subs..

I still believe more is better and medium excursion is better if you have enough drivers.. It's about moving air. HOW you do it, makes a big difference..

In the 80-90s I ran 4 Tall Boys. They were a 12", 15" and 15" passive in a 6cf Tall box. 1000 watt Daytons is what Brian recommended at the time. The passives were tuned to your room, amps and speakers with pinching putty from the passive to adjust (Q) uality. Thumb nail at a time.. Very accurate way to tune and blend a bass system.

OB Servo subs, both sides of the driver are loading and onloading the room, your ears act different.. I use 6 12" OB high excursion drivers... they work both ways not one.. Decoupling those cabinets made a heck of a difference. They are made to stack too. I ordered 2 more double 12", we'll see.

Regards

The think the real issue is what type of floor is present in your listening room, I have a dedicated room with wool carpet over concrete and I can see no reason in this case to do anything other than drain the energy by coupling. 

The last part of my career was foundational drilling for earth reinforcement. I don’t care what you have it moves and vibrates. Even 7.5" concrete on 8" friction peers every 4 feet vibrates.. Decouple everything.. Simple. There no exception to the rules. Ask any mechanical or civil engineer, isolate and eliminate where possible.

Check this out there is an overpass that was built, it vibrated so bad when a train went under the overpass for a 1/4 mile in every direction everyone was complaining. They had to go down 160 feet to bed rock and anchor with several strands of wire rope. 130 8" holes 160 feet deep they had to hold 50 ton when stressed. That is called coupling.. Spike are a pure illusion that can look OK at best..

Open the hood on your car or PU, see any spikes for engine mounts.. LOL No one who knows about vibration uses spikes.. NO ONE.. Just in the stupid stereo world.

Get an accelerometer and see for your self.. I have a PCE-VT 3800s. It tells the WHOLE story about vibration.. You can’t argue with the science.. sorry.

Thing vibrate..

BTW it's time to feed the chickens..

Regards