Allow speaker movement or don't? Spike them down or allow some movement? Brace a speaker frame so it is stiff, or allow it to vibrate like the speaker itself is an instrument?
I'm not a physicist, but I'll talk about Newton's 3rd law of motion in relation to speakers, as I understand it. This law states that for each action there is an equal and opposite reaction. The action, or force would be a constant, and movement of the two bodies away or toward each other would be proportional to the mass of each body. Speaker cone and voice coil, vs the mass of the speaker basket plus cabinet in this case.
So, when a speaker cone VC magnetic field is pushed away from the speaker magnet this causes them both to push apart, not only the cone. And theoretically they should move apart in relation to their mass. The mass of the VC and cone is much less than that speaker basket and magnet, and the speaker cabinet itself. so the cone mass will try to move proportionally to basket / cabinet mass in free space. If the speaker basket plus cabinet mass is 1000 times that of the cone and voice coil, and if the cone moves 10mm, then the cabinet should be able to move .001mm away when the cone moves that 10mm. While this doesn't seem very much, if that counter-movement isn't allowed to happen (by spiking the cabinets, for example), then the cone movement will be affected in such that it won't be able to move as freely as it should, which I believe will result in a poorer sound than with the speaker allowed to move along that axis.
I tried a set of speaker stands whose maker said it used this 3rd law of motion concept, and while I noticed that there was some improvement of sound, when the speaker was allowed to move forward and back, the way the speaker stand allowed that movement also forced the speaker to move a bit up and down at the same time, not along the main axis of motion, which to me seemed like trying to move a spinning gyroscope against its main axis. I set out to find a simple solution to this, so the only allowed motion of a speaker is along its cone-movement axis.
This is why I talked about using rollers under speakers in my Gary's DIY and Tweaks section.
http://www.audionervosa.com/index.php?topic=6615.msg83674#msg83674This is a very inexpensive and effective way to allow the speaker to move forward and back along the axis of cone movement. And I did get feedback that it tightens up bass and allows an overall better sound. However, it is possible that the speakers could slide off the rollers, so an improved approach to this could be done. I have a few ideas on that.
Another way would be to mount fixed wheels under the cabinets allowing movement along that same axis - not that expensive to do. And I'm trying that approach right now, with 3 wheels per speaker - two in the back and one in the front; not sure if this is better than rollers but it is more convenient. I do notice a positive sound difference with this approach also. And of course there are varying qualities of wheels. But I'm not completely sold on this yet - time will tell.
And now sliders. The basic idea of allowing speaker movement I think can be good. Basic sliders can be found at Home Depot, but I'm sure that Herbie's or others can be better. However, sliders allow movement of the speaker along all axes along the horizontal plane, possibly against the movement of the cone, and not just along the long axis of cone movement. I think that allowing speaker movement only along the axis of cone movement is important.
With all this being said, anything that you think improves the sound is a good thing for you.
Really glad to see that people are trying different things!
Gary