Rega MDF platter

Can anyone give me some details about the MDF platter as used by Rega on some Planars. I notice from photos that there is a recess underneath. Is this for the sub platter to fit in or is it clearance for the motor and drive belt as well? Also, is it a full 12" diameter platter? I am basing a new turntable build on Rega mechanicals and I am considering machining a new and heavier MDF platter. I just want to get an idea of how the Rega one is designed first.
 
Can anyone give me some details about the MDF platter as used by Rega on some Planars. I notice from photos that there is a recess underneath. Is this for the sub platter to fit in or is it clearance for the motor and drive belt as well? Also, is it a full 12" diameter platter? I am basing a new turntable build on Rega mechanicals and I am considering machining a new and heavier MDF platter. I just want to get an idea of how the Rega one is designed first.

Sorry this is a late reply Dave -the recess is to clear the motor and belt too.


John R.
 
MDF is a problematic material for things that need dimensional stability over time.

Moisture causes it to "grow" in one dimension (thickness) more than the other. I don't know of a way to prevent that completely.

Rega probably sealed the MDF (I would expect) in a coating or paint...

Just a heads up...

_-_-bear


MDF is available in various grades including moisture resistant, alternatively you can seal commercial (diy) grades yourself with a suitable sealer available from diy stores.

We've had great success with mdf which is used in our "Sole" sub-chassis for the Linn LP12. However, mdf in this application is used as a damping layer which is sandwiched between two sheets of aluminum. Results of damping factor tests on our sub-chassis casn be found on the audioqalia website here.. Home - Audio qualia

I dare say Rega sealed and painted their mass loaded Planar 2 mdf platter.

John R
 
Thanks for the replies. I am beginning to move away from the idea of MDF, due in part to the drawbacks you have all mentioned. However, the Corian option is an interesting one and I may look at this seriously. What I am proposing to build is a classic looking turntable with a deep platter and 60's Audio Technica arm but using more modern underpinnings that are easily available and replaceable. This is why the idea of the Rega machanicals was considered but unlike the Rega however, I am planning a suspended sub chassis.
 
That may not be the best move Dave. After hearing the Rock and the Roksan Xerxes in the '80s and preferring both- in different ways- to the Linn I had at the time, I experimented with a Thorens TD 160 I'd taken to bits and found it sounded better without the springs. It's at least partly a matter of taste, and the sound became less spacious, but the bass seemed tighter and it just sounded more 'together' musically. My suspicion that suspended decks had problems were triggered by watching a friend's Rega 3 in action, oddly enough. Not a suspended deck, but the motor seemed to be in constant motion on it's suspension/ decoupling belt. It struck me then that this must be doing strange things to the speed stability, which seemed to explain the odd bass quality of these decks. Suspended subchassis decks have a similar problem it seems to me, except in the rare cases where the motor is deemed quiet enough to put on the subchassis (Pink Triangle Anniversary) or those that have highly damped suspensions (recent Rock turntables and the SME 20 and 30 series). Just recently I modified the same Systemdek I mentioned on your AT cartridge thread from springs to using sorbothane 'blobs' in their place. Again, to my taste, much better. This was one of the original 'Transcription' decks, later versions of which were known as the 'III'. They are well known for powerful but rather soft bass, but removing the springs completely sorted this out. Slightly less spacious and less bass quantity, but better quality ad a better focused sound. I should point out that all the modified decks were either used on wall shelves or stands on solid concrete floors. All that said, if you prefer sprung turntables, go for it, but you might find it's bunch of effort for worse sound!