Idler Drive Plinth Question

[kelvinMunson]

Having looked at the graphs I am curious as to the connection between resonant frequency and sutability for construction of oceangoing ships ?

Also, I always understood that the violin body was actually designed to resonate and amplify the vibrations of the strings; somewhat different to the purpose of a turntable plinth ?

Or maybe not, since you are suggesting that there can be issue with overdamped turntables ( I think you are actually referring to overdamped plinths ?)? Do you have experience of a heavilly damped plinth actually impacting negatively on the performance of the arm/cartridge ?

[Magdadavis]

I agree entirely with cats squirrel but let me throw in another curved ball. Some material, like stone, granite, marble and concrete store energy and let it out micro-seconds later muddying the incoming sound.
I tried a slate plinth on a Linn Sondek. The bass was awesome, the mid-range dark and the treble muted, almost non-existant. Of course a Linn LP12 is a strange animal and that experience probably does not apply to most other turntables but it makes one think doesn't it?

[kelvinMunson]

So, this energy that is being absorbed by the slate and re-emitted microseconds later..... is this somehow passing through the cartridge/arm/turntable/plinth and back; or are we talking feedback from the speakers via the plinth. I have a problem imagining that much energy is going to make it from the cartridge into the slate and back ?

[aardvarkash10]

^ there are so many potential feedback loops and influences.

Mechanical noise and vibration from the drive system including the motor, idler(if any), and platter bearing.

Micro-feedback from the action of the cartridge and stylus in the record groove

Ambient noise and vibration including building movement, traffic, people moving around the building, air conditioning yada yada...

Acoustic feedback from speakers back to the turntable

And that list from the top of my head. Each has its own typical (and individual atypical) frequency and amplitude that has to be dealt with appropriately. You could end up very paranoid delusional if you took all influences into account...

[cats squirrel]

I would agree with you, JD, on the 'voicing' of early turntables, for most (if not all) were housed in wooden cabinets, resplendent with fancy veneers, and also containing the amplifier/radio and speaker/s. I have such a system, and it does produce a lovely sound, but nothing like a real orchestra! More modern decks also seem to fall short, even Rega has a range of decks of ever increasing price, with every step up the ladder comes a (hopefully) better plinth material.
I fail to understand the concept of an 'overdamped' plinth, though. Even on a panzerholz plinth, one can still detect the rise time of a scratch on the vinyl akin to a bandwidth of at least 10kHz, so there does not seem to be a cause and effect scenario between a well damped plinth and the reproduction of fast transients.
Panzerholz plinths have worked well for SP10's, not a deck associated with agricultural vehicles.
'Panzerholz' and 'resonant body' do not go together, and as Kelvin has observed, violin bodies (and other stringed instruments) are meant to vibrate, else we would not hear them.
People who have plinths made from materials fit for purpose say they are more than happy with the results, observing they are providing uncoloured rhythmic sound. What I suspect happens when people say the sound is lifeless is that all the vibrations that contributed to the lively sound have been banished, and what remains is the stark truth, which many cannot abide by. They need 'enhancement' to give them the excitment that the music is lacking.
If you need an olive to give you excitment in a glass, maybe it's time to change your drink.

[cats squirrel]

So, this energy that is being absorbed by the slate and re-emitted microseconds later..... is this somehow passing through the cartridge/arm/turntable/plinth and back; or are we talking feedback from the speakers via the plinth. I have a problem imagining that much energy is going to make it from the cartridge into the slate and back ?

The role of the plinth is essentially three-fold, to deal with the mechanical noises of the deck components, seismic and aerial intrusions. All can find their way into the plinth, so it makes sense to use a material which can damp those vibrations as quickly as possible. If inappropriate materials are used, vibrations build, eventually finding their way to the stylus (through the plinth/bearing,/platter/mat/disc route, and from the plinth/arm/cartridge route, I have measured this in one instance to be roughly 50/50 from each route, from a wooden box type plinth.

[alternativeroute]

Theoretically wouldn't a sorbothane plinth work well?

[kelvinMunson]

I wouldn't have thought that cartridge,tonearm/manufacturers design their equipment in anticipation of vibration being fed back via a resonant plinth ? That would be rather difficult to predict; don't most cartridges have a reasonably flat frequency response? So from where does this idea that you can "overdamp" emanate ?

[cats squirrel]

Theoretically wouldn't a sorbothane plinth work well?

intuitively, one might think so, but choosing a suitable material is not intuitive. One has to have some stiffness, little mass and lots of damping, be not too big, or too thick. Sorbothane doesn't satisfy any of the above.

[cats squirrel]

I wouldn't have thought that cartridge,tonearm/manufacturers design their equipment in anticipation of vibration being fed back via a resonant plinth ? That would be rather difficult to predict; don't most cartridges have a reasonably flat frequency response? So from where does this idea that you can "overdamp" emanate ?

why did SME introduce those little rubber grommets?
'Overdamping' is a mystic's word, meant to convey 'little excitement'.