What your choice speakers with spikes or speakers with a vibration isolation device?

Anyway the evidence, what there is, seems to come in the form of baffle accelerometer readings which heavily favour any compliant feet over any spikes.

Your speaking of spectral decay rates within the enclosure. A good enclosure there is really no need for that spec.

A lot of speaker repair people chime in with, decay rates, when it is such a simple fix.. Green concrete. If the enclosure sounds like green concrete it is good. Decay rates are important, for VERY old amps with no dampening ability, and poorly designed enclosures.

Undampened.. You’ll keep hearing it until tomorrow.

Same with phase shift, you or I are not going to notice the 20 hz PS, you can’t. It’s sub, you’ll feel it, or not depending. I like correction before it hits the speaker cable, not after.

A servo amp with a feed back correction circuit, is probably the fastest, to STOP, not correct the overshoot of the cone, and decay rate are once again, not an issue.. It’s an old spec. that in real world NEW SPEAKER application doesn’t matter.. Sound walls, yes, speakers NO.

Second, a speaker, mounted to the side of a taller, narrow baffle, that is deep, can rock side to side. I’ve seen it. It’s actually an upgrade on certain speakers I use. Remove the side firing woofer, and plug the space. They use to replace the woofer with a passive radiator, it still rocked the cabinet, ever so slightly.

Isolate the cabinet, decrease the vibration, and decrease the distortion, everywhere...

Think air ride, and a tractor trailer rig.. Think 100 foot jump off a building, into an air bag. and Walk away.. Green concrete and air, everything in between is an issue...

Regards

They have smaller ones for individual components, do you see a problem with floating a CD player in the air?

The magnetic field? How will that influence things... I'm always a little careful, with magnets.. Hard drives, eproms, tape decks, Reel to Reels
The steel plate in my head, my hip, my knee, my leg, my jaw, and the two screws lose in my head.. 

Bing.... Eyes Cross..

Regard

my mag lev feet Have arrived, I’ll install them and have a report soon.

The mag-lev feet are amazing! I removed the spring elevated feet that my friend made for me and replace them with the mag live feet. The range of base that these subs will take is even better than when I use the spring loaded feet. I was able to add more bass and deeper base then I expected. I put on some Earth wind and fire, turned up the volume and see what they would take. I added approximately 25% more volume into the sub and probably three more decibels from the lower range equalizer that comes built into the Macintosh MX122. It was near possible to get them to distort. I now have to figure out how I’m going to re-set my subs and higher end frequencies to get everything to rebalance. It’s pretty impressive what the coupling the speaker from the floor does to the speaker. It’s like it’s got a breath of fresh air and it breeds deeper. I’ll stop now I always hate it when guys go into goofy metaphors for how things sound. I highly recommend spending a couple hundred dollars and trying your speakers or subs D coupled,Worth every penny!