Suspended vs. non suspended turntable

OH, BOY! Now we get to spend $17K of someone else's money! While I ponder my version of a shopping list I'll throw out some more things that can be pondered while visiting the porcelain throne.

I'm not intending to pick on Dgarretson here. I'm just trying to think out loud and see if I can resolve somethings to my benefit. The more I learn the more I know how much I don't know.

If I'm taking too much of a turn from the topic of Amfibius's thread I'll be happy to take this discussion to a new one.

regarding the merit of a non-suspended TT, but sited on a platform that provides a decoupling suspension.

Adding a suspension to a non-suspended table? If this does improve the performance of any table, what does that say about that table's implementation? Flip that around to those who find that removing the suspension from a table in favor of fixed feet. Again, what does that say for the table's build or design?

But then again, maybe it is the combination of the table and what it sits on. I have found that the material directly in contact with my table has a lot to do with the performance that I get from my analog system. Either way it seems to me that we still have to make our determinations about a table's setup and performance on a case by case basis since there are so many factors that affect what we get. Analog can definitely be a tweaker's dream or nightmare.

[quote] If you can rap the rack with your knuckles and hear the sound through the speakers while the stylus rests in the record groove, then it's likely that the rack is acting as an antennae for LF vibration from earth or from AC transformers on the lower shelves or from acoustic waves from the speakers. [/qoute]

I believe the natural frequency of the earth is around 6-8Hz. Well below the resonance of most arm/cart combinations. Don't think that's going to affect much in the audible range. However, I can see that if one lived on a busy city street or had a freeway right next door there perhaps may be some transfer of noise into the table.

I can't see how rapping my knuckles, a force of several ounces or more per square inch, can indicate that sound waves can be influencing anything through my table above the noise floor of my analog system as a whole. I agree that it tells me the wood I built my rack from is relatively easily excited.

Noise from other components on the same stand. That should be real easy to measure the difference. All one needs to do is measure the response through the speakers with the components in the stand and with the components not in the stand. Very easy to find out if the difference is above the noise floor or not. This iss assuming that the sensitivity of the measuring equipment is sufficient enough to record the difference. Even if the equipment is not, and more importantly, can your ears hear the difference?

Gives me something to ponder.

Have you got any clues as to what you would like? You mention a substantial budget. What do you already have, if anything? What would you like to improve and what do you listen to regarding genre and quality of your pressings?

Dave

Dan_ed, Admittedly, it is speculative to theorize concerning the impact of extreme LF seismic activity. However, though the effect of acoustic resonance & its harmonic content at frequencies above the fundamental LF tone is unpredictable, it is easy to observe anecdotally. A subwoofer or a stereo with good dynamics propagates strong vibrations at varying frequencies throughout the room: in the surface of racks, in the floors & window sashes, in the soft pillows of the couch, through one's foot, in the gut, etc. The TT platform, plinth and arm will all respond differently to this excitement. Tube microphonics is another common example. Whatever the merit of the knuckle-rap test, failure of this test evidences that the TT has not been isolated & suggests a probability that vibration at lesser amplitude is passing through the system. I'm panglossian enough to believe that it's better to pass than to fail this test. It’s not too much trouble to devise a decoupling platform that passes the test, and in so doing one may observe an audible improvement in focus and smoothness of HF. I doubt the improvement would be meaningfully confirmed in a frequency response test. An accelerometer on the TT would probably better indicate what’s happening.

I would posit that a sprung suspension is the best way to reliably dissipate vibration into benign LF mechanical energy. The mechanics of other more complex approaches involving constrained-layer damping are more complicated to execute reliably and with repeatable results in combination with the wide variety of rooms, platforms, racks & floor compositions in general use.

As one moves up the food chain to very expensive TTs (e.g. Rockport, Caliburn, Grand Prix), an integral platform and/or rack design becomes a holistic design element. My sense is that most standalone TTs are compromised partly by cost & partly in order to optimize performance independent of siting issues. With belt-drive TTs, there might also be trade-offs between the sometimes competing design goals of transient speed stability & resonance control. As remarked by one TT pro in these forums, even small amounts of compliance in a TT suspension (such as rubber footers under a motor) sacrifice speed stability by creating an unstable geometry between motor & platter.

A suspensionless TT on top of a decoupling platform is at least one way to separate variables that affect speed stability and resonance control, and to reconcile these two design goals. I was myself skeptical of the approach, but positive feedback from owners of unsprung tables like Raven and Scout TTs (who counter-intuitively found benefits even in combination with wall racks and concrete floors) confirmed my own results with a modded unsuspended VPI TNT. If one accepts that TT and platform/rack are a system, it’s not much of a stretch to justify tweaking individual design elements in each as to logically complement each other. The question of whether this transgresses the immaculate conception of an original designer is a matter for religion.

"The question of whether this transgresses the immaculate conception of an original designer is a matter for religion."

well put!

Posts like these are the very reason I read this forum. Excellent job, Dgarretson!