loss of bass after filling stands

Hi Martin. If your marble tiles are not spiked to the floor, as suggested above, then the additional weight of the sand is probably allowing the speaker to move back and forth at a lower frequency and cancelling bass. Therefore I agree with the above posts on this point. Adding sand to a stand is not necessarily a good thing. With a speaker that lacks bass, there can be a perceived increase in bass due to filling the stand with sand (if the stand is firmly spiked to the floor. But the reason for this is smeering of the bass note, thereby creating a sense of more bass weight - which I admit can be a pleasing effect with some lightweight-sounding speakers. There can be some beneficial effects of filling with sand, such as damping of the stand's resonance (or even the floor's too), and providing a sink for the speaker's energy. But if you do fill your stands with sand, you should ensure you spike the speaker to the stand so that the energy stored in the (now heavier) stand is released quickly at the interface between the speaker and the stand.

Martin, I hesitate to be too definitive because I have found that different things work with different speakers, and can depend on the weight of the speaker. When you screw speakers to a heavy stand you ensure that the speaker's energy has a sink and that the excursion of the speaker will be minimised. The downside is that the stand will store and release the energy over a long period, and will be delivered back to the speaker very easily. If you either rest the speakers on up-turned spikes screwed into the stand, or screw the spikes into the bottom of the speaker, the result will be different. Any significant movement of the speaker will be quickly released to the stand, but will be less likely to be returned to the speaker. I certainly found that this latter method was preferable with several small box speakers (such as Totem and Proac). Principally the sound was "faster" and more open. With screwing the speakers to a heavy stand, there was perhaps an improvement in neutrality, and greater bass weight, but a deadening of the music (which I ascribe to smeering of fine detail). Where screwing the speaker to the stand may be better is when the cabinet has a "lively" resonance and the slowing of the release of this energy is perceived to be an improvement. This is just my theory and I suggest you take it as merely a suggestion for trying something else. If you end up prefering the screws oaver the spikes, then there may be a cabinet resonance issue that might be better dealt with using Vibrapods between the stand and the speakers - I only say might because Vibrapods have their pluses and minuses. But all of this is predicated on you spiking your stand securely to the floor first - which really is a must.