loss of bass after filling stands

Why didn't the B&W dealer recommend the B&W stands that were made for these speakers? My 805's sound tight and relatively deep with the matching stands. The coupling of the speaker to the stand with screws may be a part of it. Also, you may want to try a combination of shot and sand, it may be over dampened as JD and Metaphysics suggest. Macm makes a good point as well. Let us know how it all turns out. Good luck.

I tried marble over carpet with spiked (sand filled but still very light) speaker stands, resting on the marble and it sounded very thin, though clean, to the point that I kept turning up the volume way to high for my amp. I removed the marble from the equation and things sounded much fuller though a bit rougher. My floors are some type of heavy plaster (kind of like Fix-All) and should be somewhat similar to yours. The stands were by Anaconda with a single round support post which is why they were still relatively light after being filled. Now that I have switched to very heavy/massive stands I was thinking of trying the marble again. I have alway found it necessary to play around with the speaker placement after changing most components (including tubes, stands and IC's) in the equation. Nothing drastic usually just a few inches or a few degrees of angle at the most may end up sounding better to me. My speakers by the way are not optimaly placed by any means, but I will take any improvement that I can get.

Spiking and filling your speaker stands may give you tighter bass, but not the deepest bass your 2 way speakers are capable of. Place vibrapods between speaker and base
and you will experience deeper more extended bass.....only takes a couple minutes to try. Floor standing speakers are a different matter.

which stands are the ones you have BMPNYC?

Soundwatts, the stand made specifically for the 805's model number is FS-N805. Try going to
http://www.bwspeakers.com/products/ and click on product gallery. When you see all of the Nautilus speakers, you will see the stands as well. They are a perfect fit, with the same contours and the same oval shape as the 805's. They are very well made, as well as elegant. Maybe your dealer will allow you to exchange the speaker stands. I have the silver stands with the 805's in the natural cherry finish.