Springs under turntable

A good fraction of the energy that causes speaker cabinets to vibrate is coming from the back wave(s) of the drivers in the box, which is an issue separate from holding the drivers stable in position and a reason for the many ported speaker cabinets, which is an attempt to dissipate the sonic energy without exciting the cabinet.  I've always favored Transmission Line woofers, partly for the reason that such designs excite the cabinet very little, resulting in a very clean output.  The only woofers or subwoofers that I have successfully mated with my ESL speakers have been TL types. The cabinets of my home-made TL woofers that I use with Beveridge 2SW speakers are constructed of 1.25" thick HDF and weigh about 100 lbs each.  They don't move.  But given the fact they are TLs to begin with, they aren't very excitable, either.  Maybe this helps explain why I say that there are two separate issues with vibration and resonance.

@mahgister,

I've experimented with weights on top of speakers in the past, not on springs and found that it's easy to overdamp the cabinet. Not always a good thing.

The box has to hold the body of the speaker stable so that the energy generated by the amplifier to move the cone is converted only into motion of the cone. This is never perfectly achieved, of course.

The answer to your question is in the "this is never perfectly achieved"...

There is some critical value where resonance and distortions increase, and a treshold under which the distortions and resonance dont implicate an audible effects...

Putting springs under speakers isolate so much well from the other speakers influence and from feed back effect from the floor and from other external vibrations, then the audible effect is beneficial because the movement of the cone is maintained under a critical threshold...The isolation from external influence is less detrimental to the cone movements than some internal resonance from the speakers box without isolation coming from these external factors ,especially from the other twin speaker in the room...

It is not the case when speakers are not isolated properly.... It is the reason why springs are very useful.... Before i use springs i was using my sandwiches of different materials, that was good damping and complementary coupling and decoupling but not so powerful radical decoupling than springs.....The audible effect was way better than using nothing, but a smearing of the sound subsisted that was erased by the presence of the springs....

I’ve experimented with weights on top of speakers in the past, not on springs and found that it’s easy to overdamp the cabinet. Not always a good thing.

This why God gives me ears: to adjust the weight of the damping mass.... :)

And i use the same ears to adjust the compression of the springs by adding mass to the speakers... It takes me 3 tryings... First not enough: then harshness accent on high frequencies, after that too much weight and darker sound too much accent on the bass or mids bass....

The last one experiment were perfect playing with 2 mass of 5 pounds  ....The critical difference were around adding or substracting 5 pounds of weight on 100 pounds of total mass(speaker mass +concrete slabs)...

@mahgister,

What type of platform are your speaker on and how is it supported?