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coupling or decoupling of vinyl to/ from platter

Dear all,

I'm puzzled by a number of claims about record clamps and mats. 

I own an old Rega Planar 3, and I was reading about the importance of coupling the record to the platter, to add effective mass to the record to reduce vibrations, slippage etc, and improve the solidity that the groove "image" presents to the stylus. 

I also read about the importance of de-coupling the vinyl from the platter to prevent the transmission of unwanted vibrations from the motor. Rega has a very dense platter made of glass with a fluffy felt mat on top. So, felt to decouple lp from platter, is that right? 

Then, I purchased a cork Music Hall mat, which has a dozen raised cork discs on the mat to BOTH "decouple" the lp from the platter and "grip" the lp.  Music Hall claims that clamps are unnecessary with this mat because coupling discs, etc. I also, without knowing this, purchased a Rega Michell record clamp. The clamp seems to do good things regardless of the mat, and of course evens out warped records a little bit. 

There needs to be, it would seem, a clear objective answer to all of  this from an engineering perspective. Coupling does x, and decoupling does y.  If you look at all the high-end turntables, they have massive platters and clamps. So coupled mass is good for flywheel effect and also  for presenting a solid "image" to the stylus? 

Either Rega and Pro-Ject are dead wrong with felt mats, and have been runaway successes in spite of this, or the felt is adapted to their setup: weak motor, relatively light but super-dense platter, and decoupling felt to manage the motor and rotational noise transmitted up the spindle, and to hell with coupling?  

I did some quick and tentative experiments with the Music Hall mat and clamp vs. Rega felt mat with clamp. I need to do more comparison. The results are different but hard to characterize. I'll post again with more comprehensive subjective tests. 

From an engineering perspective, which should be best, Rega clamp w felt, Music Hall mat by itself, or "screw the mods, Rega it great just the way it is, heretic!!!" ?

Let the games begin!

Paul

paulburnett
atmasphere's avatar
atmasphere
11,810 posts
 
If the LP has to be decoupled from the platter to get rid of motor noise, the turntable has a really serious problem and should be repaired.

I think we can discount that explanation.

A proper platter pad does several things at once, that is if its intended for best reproduction as opposed to DJ service:

damp the vinyl
damp the platter

To do this properly the pad has to be very nearly the same hardness as the vinyl, to avoid reflected energy. Yet it has to have damping properties.

You can see right away that bare glass or metal is too hard and won’t damp the LP properly. If the mat is really doing its job, the stylus tracking the groove will be relatively mechanically silent. The purpose of felt platter pads is to act like a clutch so the platter can rotate while the LP is held still. This is for DJ work; such pads can improve the sound if they are interfacing between the vinyl and the bare platter but other materials can work much better.
effischer
560 posts
 
As always, atmasphere has the straight story.  I bought a Planar 2 new in 1981, and its glass platter was thinner than the 3.  Accordingly, the standard issue felt mat wasn't quite thick enough to get the VTA into a decent sounding range.  I went with an Audioquest Sorbothane mat and clamped my vinyl with an AQ clamping weight.  Took out some warpage, dishing and pretty much killed all resonance.  Used the rig with a Dynavector MR23 Karat LOMC to very good effect.  Others here have had very positive things to say about cork with Rega and others, so you might want to research the archives for more info.

I never got an opportunity to try a cork mat; didn't have any dealers vending them at the time and I wound up upgrading to a Sota Sapphire in early 1984.  Its mat was both resilient and non-resonant out of the box.  I fitted a Magnepan Unitrac I to it, so never had to worry about VTA again.  I did find that the AQ clamping weight wasn't quite right, so I went to the Sota I-Clamp (low mass screw type compression) and was happy for a number of years.  Even so, the I-Clamp was awkward to use.  Found the Sota Reflex clamp second hand at a very good price and love it.  I highly recommend it for use on any table.

Either way, have fun and enjoy your Planar 3 - it's a very nice unit!
williewonka
3,075 posts
 
I had the Planar II with the 10mm glass platter - it rung like a bell - sounded awful.

I also tried the sorbothane mat  and it quelled the ringing and I was happy :-)

Or so I thought, but when compared to other TT's it sounded lifeless

I've since ...
- ditched the glass platter for an acrylic platter - no mat and no more ringing
- added a Thorens Stabilizer weight - to keep the album spinning with the platter (not slipping) - improved dynamics
- replaced the plastic sub-platter with a metal one- improved clarity
- replaced the plinth for something that actually works - it stops ALL vibrations
- replaced the arm with one that actually works well - it got VTA :-)
- OK - the lid works well - so I kept that - and the on/off switch

The result: - clear, detailed, dynamic and precise reproduction.

It's no longer "a Rega"

 BUT, I'm really happy :-)

Regards - Steve



reubent
6,996 posts
 
I've also been curious about this. I have a Pro-Ject Debut Carbon DC Esprit SB with an acrylic platter. It shipped with a felt pad and I've used it with, and without, the pad, but never really paid attention to any sound quality or noise differences. However, I've seen a few very nice leather pads that look awesome, are thinner and should provide a bit better traction for the LP on the platter.

Anyone have any comments on using a leather pad? Also, I'm not currently using a clamp/weight. Is this something I should try? Is a simple weight OK? I don't want to put too much pressure on the spindle every time I install the device.
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