Springs under turntable

@mahgister 
Many others have also reported sonic improvements when decoupling speakers and the Townshend folks believe springs and air bladders are two of the better decoupling methods, although there are other methods such as using Herbie's products, roller bearings for decoupling in the horizontal plane, etc.  I believe the physics are likely complicated based on the many variables involved with specific applications but regardless, quite a few who have tried decoupling believe they hear improvements including folks like Jim Smith, author of Get Better Sound
https://www.amazon.com/Get-Better-Sound-Jim-Smith/dp/0982080700/ref=sr_1_1?dchild=1&keywords=get+better+sound%2C+jim+smith&qid=1599172058&s=books&sr=1-1

I'm guessing you're hearing more air around the instruments? Those likely are resonances we seek to eliminate.

First thing I thought of. I know where you are coming from. But the sound quality is improved at low volume too. My rig is pretty solid and heavy in the right parts. Environment is concrete. Instruments are precisely focused and tiny details are more apparent without glare or blur. I think your guess may be incorrect. Thanks.

mitch2

Thanks for the book recommendation....

My best...

The physics is complex yes...

But in a word springs isolate the box from the external vibrations, then there is no more resonance between the 2 speakers in the same room...In my case on the same desk....

Internal resonance are probably less enhanced and decreased without any external influence to amplify them...

This is not the explanation for sure just my 2 cents.... I am not a physicist....

No doubt in my mind that with the right compression applied(i tried 3 rate) it is simple for the ears to discern the best compression , too damping weight on the springs and the sound is warmish or muddy, not enough damping weight and the sound is too bright or too harsh...

Right amount and all is improved on all frequencies...

This is audibly evident.... My ears rarely doubt...Perhaps they are easily deluded but they never doubt... :)

If the speakers are correctly isolated, suspended, then the larger transients that produce energy storage in the cabinets, aught to deform the isolation device through a broad frequency range.

Correctly implemented the high frequencies aught to clean up as does lower frequencies, the cabinet swells and contracts as it will, but relative to the substrate, the goal is to have it’s center of gravity to remain as motionless as possible relative to the substrate.

When correct implementation of zero stiffness on loudspeakers is administered, there is no question of the superiority of this engineering practice on the voicing of the loudspeaker.

Please go ahead and try it, you may just realise a significant bump in performance for what is relatively one of the cheapest upgrades possible.

In correctly isolating using compression springs, (obviously not an issue if hanging from springs), the center of gravity can without a great deal of force, be moved across and outside the base. Short squat sub woofers are much less prone to being knocked over and damaged than speakers where the center of gravity is higher over a narrow base.

The springs themselves, under compression should also have a centralized load bearing low relative to it’s base, unless constrained as in the spring array mentioned above. I generalise that the diameter aught to be close to the final load height of a compression spring for the sake of stability, in this particular use.

The more rigid the substrate, the higher percentage of energies will deform the isolation device, such as a spring. I choose springs because of their broad range of isolation, relatively inexpensive, and easily acquired.
Correct spring rates and geometry are not hard to find, as springs are the most commonly used broad range isolation devices used worldwide.

@mahgister 
I suspect variables related to the success of decoupling speakers include the floor (i.e., concrete or suspended wood), the weight of the speakers, the stiffness and resonant frequency of the speaker box, the force generated by the drivers (i.e., larger woofers create more back pressure than smaller midrange or mid-woofer drivers), whether the speaker design is acoustic suspension or bass reflex, if and how the speakers are mounted on stands, the weight distribution of the speakers (i.e., heavier in the front?), and other variables.
I suspect factors affecting the decoupling medium include stiffness, number of coils, and degree of compression (if using springs), pressure, volume, and elasticity (if using an air bladder), hardness and elastic properties (if using an elastomeric material), and the ability of the medium to decouple in the horizontal plane as well as the vertical plane. 
Manufacturers of things like spring supports, air bladders, and elastic support materials often give weight ranges to help customers select the right product but it would be very difficult to precisely account for all variables.  This may partially account for differences in the degree and types of improvement heard by listeners using decoupling devices.   Since most report hearing positive changes, it is probably a case of close enough being good enough.