Best Isolation Device for Speakers?

Sir I beg to differ. In your proposal there is no provision for resonant energy to leave. The resonance will come out the front the back the sides. You will have a 360 degree resonant pattern to augment the music..Tom

Theaudiotweak...Enclosures should be solidly constructed of "dead" material, shaped so the panels don't vibrate, (cylinders are good), internally braced, and internally damped. If the top/sides of your enclosure vibrate, even glueing the bottom to a concrete floor wouldn't help.

Of course, the real answer is to get rid of the box entirely: go planar.

What is the best material to put under the speakers? I've got some B&W Nautilus 803's and I can buy Sound Anchor stands for them. I've read that putting BDR IV cones under the Sound Anchor stands is an improvement.

Perhaps putting a 2' x 2' sheet of granite, tile, hardward would be better?

I am most interested in what is going on here. When the speakers are spiked onto the floor, this should create the best path for resonant energy to depart (good), and this should increase the energy input into the floor which drives the natural floor resonance (bad). Putting the speakers on MDF over the carpet should reduce both the good and bad effects above. This is the dilemma.

I can notice this dramatic improvement when listening to a female vocal with delicate symbols and piano in the background. So there are no heavy bass notes that might be shaking the speakers or the floor. Also, for what it is worth, I can easily feel the floor resonate around 30HZ when conducting SPL measurements. However, the I have adjusted the subs in the 5As and have a smooth response from 20 to 160 HZ within +or- 3DB.

Yesterday I bought some heavy cutting boards to try under the speakers in place of the MDF. I am just trying to confirm what I am hearing with another material. I would like to try the Systrum platforms, but it would seem to raise the speakers up too high for proper listening. With regard to hanging the speakers on wires, these 5As weigh 185 lbs. each!

I spoke to Richard Vandersteen at CES about this and he doesn't like putting the speakers on MDF because he felt they would not be stable enough (movement front to back that would distort the image). His answer was to strengthen the floor from underneath.

I'm still trying to figure out where to go next. Thanks for your ideas.

Zargon...When isolating, the heavier the better! Ceiling joists are similar to floor joists and can easily handle several hundred pounds. In your case I don't think that the fishing line would hack it, but decorative chain, rope, or wire would be fine.