Springs under turntable

My nobsound spring isolation feet arrived Sunday, late afternoon. I got them, hoping to alleviate some subwoofer influence on my turntable. I'd noticed some subtle muddyness in louder bass passages with vinyl that I did not detect when streaming the same tracks.
After reading several reviews and discussions, I assembled the feet with only 3 of the possible 7 springs in each foot to accommodate the 20lb weight of my Technics TT.
For starters, I chose Boz Scaggs' album "Dig" which has several bass-heavy tracks including:
"Payday", "Miss Riddle", "I Just Go" and "Thanks to You".
The tracks still had good dynamic range, but the low end was less muddy or boomy...revealing better detail.
Classical music was better too....
STRAVINSKY: THE FIREBIRD SUITE (1919 VERSION)ATLANTA SYMPHONY ORCHESTRA AND CHORUSROBERT SHAW, CONDUCTOR has passages where the bass and kettle drums come on strong. The accompanying woodwinds and echoes of the hall are more noticeable now.
Don't have any "cons" to report as of yet...still listening for any issues.

I copied the album info, so forgive the all caps! By the way, this Telarc version of the Firebird Suite is outstanding. Some of the best orchestral reproduction I've heard. At times, startling realism. 

mwinkc, I have that record. Lots of fun. I think they stuck the microphone in the kettle drum, makes my windows rattle. 
Isolating any turntable from the environment is essential for the best playback. The springs act as a mechanical filter. All frequencies above the resonance frequency of the system will not get through to the turntable. All frequencies below will get through. This is why the recommended resonance frequency is below 3 Hz. If you have ever played with an AR turntable or the LP12 that is pretty wobbly if not done right. Both these turntables use exactly the same suspension design. It was a good start but there was substantial room for improvement. Sota made the first stable suspended table in 1980 or so then came Basis and SME. All these tables have chassis that are hung from springs instead of sitting on them. The Solid Tech Feet of Silence are the best aftermarket springs I have seen if your table is not too heavy. The feet are hung from their springs. They offer two spring rates and two different kits of either three or four feet. Any turntable that is not already suspended should benefit. 
The next evolution is suspension design is MinusK's negative stiffness design. It isolates down to 1 Hz remaining reasonably stable. 
It was designed for delicate lab gear like Scanning electron microscopes.
I find it interesting that lab gear that is totally electronic does not require isolation.

I ended up using Symposium Rollerblock Jr’s in place of the springs. It was a revelation!

Use both, that’s what I’ve been using for awhile now with great results.

I had custom roller blocks made locally based on well known existing designs. The latest version from Ingress were not designed yet/available at the time I made mine but these are basically what I had made . These look to be of excellent quality and the mirror finish is a bit better than mine (which is important).

My sandwich is 4 springs on the shelf/platform > .75 mdf > 3 roller blocks (open face) > .5 marble (polished side down) > component. I have been wanted to try a symposium svelt shelf or equiv in place of the marble, but haven’t got around to that.

Its key that the total weight compresses the spring close to its max load.

@frogman When you say a Target shelf, do you mean the brand?

I have found that for the springs to correctly isolate the loaded mass, that substrate needs to be unyielding, well as much as possible.
In a situation where the structure under the springs is prone to vibrate due to materials, geometry, etc. I have no doubt at all that it could be accentuated by the springs the effect like cars and trucks creating corrugations in a road, where the specific frequency is made worse.

I have absolutely no doubt that what you claim happened.

Using springs for isolation requires planning and some knowledge.
mahgister, yeah tuning with mass, great idea - just like derekw_hawaii suggests. If you can't get the perfect springs, get the perfect load.

And I suggest, try to shore up the substrate under the springs?

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