A lot of information and opinions on the subject available here and at Audioasylum.
****I have often wondered if the performance could be improved with a non-spring suspension.****
The answer is YES; but, with a big caveat. The sound of the turntable will most definitely be changed by removing the springs. Wether that change will be perceived as an improvement will depend on how much vibration your rack or shelf transmits to the table's feet. I am generalizing, but a general rule of thumb is that the "springier" the suspension is, the more it will isolate the platter/ tonearm/cartridge from vibrations. The stiffer the suspension, the more that vibrations will be transmitted. Stiff suspension also usually means a tighter overall presentation with better defined images and tighter bass. A springier suspension usually means slightly more diffuse images, somewhat bloated bass with slightly less extension, and (interestingly) a band of brightness in the upper midrange with a welcomed sense of rhythmic liveliness. A very important factor at those point is how loud you play your music. The louder you play it, the more pronounced these effects will be up to the point that you experience acoustic breakthrough (feedback). Just because you don't actually hear feedback does not mean that the playback is not being affected negatively; it may be on the verge of feedback and causing problems.
I had my various HW19's on a wall shelf which, while it fixed my springy floor problem, also transmitted a fair amount of vibration to the shelf because of a lively wall. I tried just about everything in place of the stock springs: stiffer springs (VPI), Navcom, Sorbothane, upturned metal cones, foam, wood. What gave me the best results (and what I settled on) was original Sorbothane pucks with a short "Tiptoe" cone pointing up and inside the puck's recess. Bottom line: as usual, there is no one answer. Experiment! And don't be seduced by a change in the sound that may end up not being an improvement at all. Good luck.
