Springs for homemade isolation stand

"If I knock lightly" - the best way to eliminate this feedback is don't knock at all! :-)

You are creating a condition that does not exist under normal user circumstances. Most of the acoustic problems from vibrations come from airborne vibrations which are not simulated by knocking, or airborne vibrations transmitted thru the floor which again are not simulated by knocking.

I'm not sure what type of TT you are using, but I have found the best isolation for both spring and unsuspended TT's to be a solid platform of materiel with little likelyhood of resonating in the higher frequencies, placed over soft materiel, like sorbothane. You can make a sandwich if you like. Supports with air bladders instead of sorbothane materiel can work quite well also.

Springs will resonate/vibrate a lot easier than a set of vibrapods-which I can't call expensive.

Dgad,

Calculating the resonance frequency of a spring with unknown physical properties is impossible. There is no way to predict whether the outcome will be better or worse, save by trial and error.

Springs also introduce the possibility (certainty) of lateral motion. This could have positive effects but for a TT I'd expect the net effect to be negative.

For beneath your Hyperspace I'd suggest three Stillpoints with risers and inverted risers. You can see them on the Teres website with the model 320. They worked wonders for the noise floor of my 265 and 320, with no real sonic cost in dynamics. Highly recommended for isolating a high mass table from floor/stand vibrations and dampening plinth vibrations at the same time, without allowing unwanted movement.

Placing a 2" thick piece of maple on top of HVAV cork sandwiches (the cork is sandwiched between rubber) works well.

As I've learned-garnered information from others who are certainly more wise, and experienced than I am, the consensus seems to be that any type of tweak platform-material placed between the Turntable, and Rack-Stand will make a difference audibly.

Now whether that difference will be beneficial, or detrimental may vary in every single instance-application.

Hypothetical instances would be that perhaps one person notes a great improvement using a Sand Filled Base, or a Base with Air Bladders, with no detriment to clear mids, and highs. Another-others may find that the Sand Base-Air Base has perhaps ruined-or I should for a better term "Diminished" these above mentioned qualities of their Table.

There's so many things one can try without necessarily breaking the bank. If the Table isn't quite so heavy, maybe just two sheets of MDF with a cheap piece of fine bubble Bubble Wrap in between may make a notable improvement for isolation. Tennis Balls, Ball Bearings, Maple Butcher Block Bases, etc etc.

From an engineering standpoint, it seems to me that many table, and stand manufacturers seem to get a synergistic benefit-improvement with the use of sandwiching dissimilar materials. Things like Cork, Sorbothane Sheets, MDF-Stone, the material list is almost endless.

And then the final aspect can be appearance, and beauty.

Most high end systems are usually displayed-used in one's best room of the house. One crazy example might be taking a brand new VPI TNT-HRX Table, and have it sitting on four $2 Cinder Blocks from the Home Supply Yard. While the the Cinder Block may make an audible improvement, it certainly won't do much to compliment the beauty-aesthetics of a $10,000.00+ Turntable System. Mark