Any new ideas on an old theme?

If you don't need more than a 12" x 12" footprint, there's another much cheaper way. Head to your local Lowe's/Home Despot and pick up 6 flor tiles in your stone of choice: marble, black granite, etc. Epoxy three together to get desired thickness of plinth, with the added bonus of "constrained layer" technology. Heck, you could even mix and match granite and marble for the "zebrastone" look. Under $40 per side, including glue and tax.

There have to be bigger tiles out there too--e.g. 16" x 16"--but they're not sitting on the shelf at my local Lowe's. FWIW.

I agree with those above that if you have a suspended floor, you may well benefit from some isolation between the speakers and the floor. I had that problem in a previous room in spades as the floor had a natural resonant frequency around 32hz. After many trials, I found that a combination of slate under the speakers and a post under the center of the floor (in the garage) worked best.

I obtained 2 - 7/8" thick pieces of black slate 18"x24". The slate was heavy and relatively smooth (much more so that the slate typically used in a yard environment), however, as long as you have 3 spikes the smoothness is not critical. These pieces cut and polished on one side with finished edges were about $300. I also obtained an oil which when wipped on turned the slate a rich and shiny black which really looks great. To finish these off, I put some 12"x12" self adhesive vinyl tiles from HD on the bottom of the slate cut to fit. This allows me to move the speakers around on the carpet much more easily than with the relatively course unpolished bottom side of the slate.

The heavy slate on carpet/pad gave the needed isolation while still providing stability. The floor resonance was dramatically reduced and the bass tightened up considerably. This same result may be possible with slabs of heavy wood or butcher block as well, and I will be curious to learn what you find out.

I just placed a buy it now on ebay for two pieces of granite, 12x12x1.25 in. I'll be sticking them under my speakers and probably use blu tac between speakers and stone. Will get back on the results.

OK... SO HERE'S WHAT YA CAN EXPECT FROM ABOUT $5 OR $10 WORTH OF BEECH/BIRCH 3/4 in. plywood....

Better. Lots better!

I had some pieces cut to fit all my speakers, sub, and speakers on stands, by an added half inch or so all around.

Put them under each unit and placed them back into their orig positions. Waited a few days for them to settle down into the pile a bit more and turned on the sounds.

Using the same default tune box of late, the Onkyo HT Receiver, Odyssey Stratos SE amp, Bel Canto DAC3, and Sonata IIIs, things were instantly improved. Well, minus the couple days waiting period. lol

I found the sound stage to have now, better depth, become broader and it had slightly closer to the LP a tad. The boomyness of the bass was quite attenuated... but still had good impact. Tones weren't skewed or spotlit, and the bandwidth seemed quite evenly fulfilled. Overall, a clearer cleaner presentation yet all the while, retaining luster and involvement.

A note on 'tightening' of the bass and losing the boom... I believe more listening is required here but it seems to me the tightening of the bass so many refer to is actually due to some attenuation... or loss. mostly in the prominence region or presence... the impact was sure there given my moderate listening level session, but I feel certain that along with the tightening up of the bass, came some bass db loss, as odd as that might sound

I hear and read this salutation wehn it comes to reckoning with the bass area very often, and feel it’s this way... "Yep, less boominess no doubt, but with that came less perceived bass being there". Which to me indidcates some attenuation... turning down of the bass area's SPL".

Overall, though, and this is likely a perceptive item anyhow, I think bass was improved by both addition and subtraction. I'll spend some time concentrating on the CD's which have fine bass and get back here with that... so for now, all I can say in truth is the bass is currently different. The rest of the sonic realm as I said is improved by more than a fair amount.

So it sure does seem as though there is something to this idea of platforms under floorstanding speakers residing upon hollow floors... or at least non solid foundatios... 'foundatios'? That must be Italian for foundations.

...and for less than $10, it was a step in the right direction!

You could try turning the speakers around and facing the wall.
You maybe surprised at the sound.