Rel Does Not Recomment Isolation Stands

No footers or stands on mine and it doesn’t rattle the floor nor the walls. Wood floors on a wood deck 1st floor of a two story house. 

Full disclosure, I'm not hobbyists. I've produced subs, bass bins and horn loaded bass enclosures for over 45 years.. I've sold, traded and modified all kind of others manufactures price point builds.. There are FEW that come close to my crazy collection of designs. Not EVERY sub is for every situation..

Bottom firing SUB are kids stuff plain and simple.. I don't mean to hurt anyone feelings. The KIDS are even decoupling their bass enclosures in their cars. Mass loaded with springs on the top and bottom..

You cannot decouple a sub with a bottom firing driver if it is just hanging there. Without a butt plate or being in a slot, the floor is going to be a huge out of time passive radiator and the FIRST reflection point for the subs.

I didn't make the rules I just work with them and not try to defy what you cannot change. Everything vibrates no exception to the rule.
Direct the pressure away from the floor and decouple the drivers from the rooms surfaces.. IF any manufacture has a better idea I'm all ears..

If you want to make smooth even bass understand boundaries but the right ones, the walls more so than any. Different size or different distances from the wall vs the driver location.

Regards

Regarding REL subs what they say for their , or any down firing sub, makes sense.  But not for other subs perhaps?  Re Harbeth, there are two approaches to vibration / energy make something heavy so it doesn't vibrate, make it light so it does.  Harbeth use the later approach.

Ultimately, I think it comes down to personal preference and your home situation.   I don't doubt that REL is correct about isolation.   I actually posted this question to REL support before I was going to purchase the S/812, and found out that it has a down firing driver.   I live in an apartment building and was concerned about vibration and noise transmitting downward.    So I asked about using something like the Auralex SubDude and this was the reply I got:

"We recommend placing the subwoofer directly on the floor and allowing it to couple to the floor. The feet on the subwoofer are specially designed to place the down-firing driver at a specific distance from the floor to achieve optimal effect, and altering this distance by placing the subwoofer on an isolation platform can have a detrimental impact on the performance of the passive radiator. That being said, the front-firing active driver produces far greater output than the down-firing passive radiator, and in our experience if your main loudspeakers are not disturbing your downstairs neighbors then the addition of a carefully setup and tuned subwoofer should not add any extra disturbance."

I ended up purchasing the S/812 and the Auralex SubDude anyway, and have no complain about the performance.   I rather have a peace of mind and enjoy my music and movie then having to constantly worry about whether I am disturbing my downstairs neighbor.  Also not everyone enjoys earth shaking bass, and some prefer isolation to reduce floor rattling.   Just read some of the comments on Amazon on Auralex, and see how many people are happy using one.

Anyway, that's my 2 cents.

Things will vibrate regardless of weight. Worst possible scenario is a speaker with thin walls that vibrates. What do you think the cabinet does when it vibrates?