Technics platter mat design and azimuth setup

[Teleton]

If I put a straight edge e.g. ruler across my Technics SLD150, then I see that the mat gradually thins out going towards the middle. So when mounted the LP creates a hollow area underneath. Why did they design it this way?

If I set azimuth at vertical then I am happy. If I then put a clamp or weight on the centre I am playing the majority of the record with azimuth out.

No mention in any Technics manual about this hollow, surely this is is detrimental to the sound? Maybe not?

Any thoughts on this mat design? Do after market mats resolve this?

Steve

[graham67]

A quick solution would be an oyaide BR-12 which works well on the techie. Cheaper options probably available too.

[Teleton]

Cheers for the reply Graham. Oyaide products look high quality to me, wasn’t there a metal Br12 once, looked like a sports car shiny brake disk.

Hope they are all perfectly flat. ;)

[krugdoktor]

Hope they are all perfectly flat. ;)

They are NOT. The design of the Oyaide mats is intentionally „dished“ and they must be used with a weight to allow even „dished“ records to lay in full contact with the mat.
After all the BR 12 rubber mat works as advertised and „sounds“ fantastic on my Technics 1200G (far better than the original mat)!

[Teleton]

Thanks Michael,
So that is indeed interesting. I don’t believe sellers of these Mats always explain that the weight is a default requirement. So can we identify the design reason for the dishing?

It is very important and it means that perhaps I should put my Sl150 dished original from 1976, mat back on, and not use my totally flat cork/ leather combo?

[Teleton]

...also Oyaide must have researched the best azimuth angle for their mats other than 90 degrees. I guess we are truly into the ‘art’ of vinyl replay here. I can alter azimuth with one of my head shells to experiment.

[krugdoktor]

I think most of us have a lot of experience with warped records (insufficient cooling time after pressing, foil packing of the new record too tight…). These warps are most of the times not correctable with a weight (except for the mighty expensive outer rings or vacuum holddown) and have to be accepted :steam:
But more often you find dished records which laid on a flat mat with the convex side up do make contact with the mat only with a very small portion of the surface of the record. Even worse when laid with the concave side up which means only the center of the record is supported and the rest is in free air.
Both shortfallings are adressed by the concave platter mat and a record weight.
My suggestion is: use your original mat with a not too expensive record weight https://www.analogueseduction.net/record-clamps/analogue-studio-stainless-steel-record-stabilizer-clamp.html which is heavy enough to flatten a 180g record and see if you like it.
Azimuth can usually be adjusted at the headshell-arm connection as there is most always a little play in the SME-type connector. Alternatively a headshell with adjustable azimuth can be used.

[Teleton]

Nice explanation, thanks. I see the weight/clamp is my friend here. Thanks for the purchase suggestion, however given that my sl150 platter rings better than most actual bells, I need some damping and so the mr12 (butyl / tungsten) and Oyaide weight may offer the right answer. There again we are talking the difference in £250 v £40, and that £40 is Xmas present range!

[krugdoktor]

I have the Kuzma ebony clamp (horrendously expensive), the Stillpoints LP1 (bought used, but still expensive) and the mentioned £40 weight and the difference (if any) is very small. Maybe the Oyaide BR 12 is so good at damping the record that the clamp does not matter :scratch:

[Teleton]

Well that is high praise indeed for the £40 weight. Yup it’s going on the secret Santa list. Thanks for the recommendation, it looks good and has good reviews too.

How do you set azimuth with a weight. Trial and error perhaps?

[krugdoktor]

As Peter Walker once said: wire is wire! (just kidding!), a weight is a weight!
I set azimuth with a perspex block with a pattern edged in it https://www.amazon.de/Qiman-Record-Messung-Cartridge-Azimuth/dp/B07G82NVVS/ref=pd_lpo_504_t_0/258-7983308-3664534?_encoding=UTF8&pd_rd_i=B07G82NVVS&pd_rd_r=1a104723-6826-4c43-be82-9a8e9eb60c90&pd_rd_w=NONXK&pd_rd_wg=9OASQ&pf_rd_p=d5c9797d-0238-4119-b220-af4cc3420918&pf_rd_r=K94CJ16C495V99P80JWF&psc=1&refRID=K94CJ16C495V99P80JWF and a lightweight extension f.e. a pencil lead on top of the headshell.

[Teleton]

Peter Walker? Sorry I don’t know of this fellow. I did google the name and I got https://walkeraudio.com/product/record-clamp/

My favourite high end turntable website that I will never be able to afford any of their products...but I read their knowledge and respect it.

$2200 for a record clamp, with diamond crystals. wow. These guys are incredible, and I have actually followed their crystal recommendation with my own quartz crystal experiments (found in my back garden whilst digging the foundations for my pizza oven project) with crystals blu tacked to my head shell to see if sound is improved, by a reduction in RF/EMI.

With a Osawa mag head shell, silver litz wire on the sl150 Sme3009, it did make a difference. The sound became just beautiful, allowing the Nag MP50 to shine.

I use a head shell spirit level from Johnny at Audio origami. Thanks for the link though.

[walpurgis]

Peter Walker? Sorry I don’t know of this fellow.

Mr. Quad.

[Teleton]

Gotcha, Geoff. Thanks. A genius in the hi fi world then.

[Fergus]

I read over on another forum that there is supposed to be space between the record and the mat. It's designed this way.... (?)

[Teleton]

Hi
Fergus, now that’s interesting. I see that the Sony designers also focused strongly on mat design. The ps4750 had a moon mat, did those circles have some suction effect? This would be a design consideration to prevent record movement, very different solution to a clamp/weight solution. Then I see the top Sony mat was the oil filled one, and Sony actually say to reduce vibration! No dishing effect on Sony mats!?

So I’m seeing 2 requirements- 1. Prevent vinyl slippage and 2. Reduce vibration.

Anymore requirements a mat should meet?

Maybe a space undeneath as you have observed Fergus, but why?

[Pharos]

This is good stuff, analysing and questioning the mechanisms involved.

[Teleton]

Haha, ta Dennis, the mat issue burns up sooo much thread space everywhere. I’m not helping either! Sorry server. Just an itch I need to scratch, just haven’t seen the requirements and design logic listed fully to meet said requirements.

Michael has convinced me of the dishing and clamp solution for possible warping effect, so I guess clever Technics designers did the mat dishing for good reason...I haven’t seen Technics print, oh and we’ve designed it this way so you can buy a clamp weight and get a solid surface interface...? ...but they would have to say also your gonna have to compromise the 90 degree azimuth...which I thought all cartridge manufacturers designed for?

[Pharos]

It's all a compromise, but optimisation is the aim.

Strictly a dished record will have altered playing radii, and so pitch will be affected as well as azimuth, and it goes on and on with the variables.

It does seem sensible to me to have an inset to allow the larger record centre to be accommodated and the grooved surface to rest fully on the platter mat. Many top decks do not do this.

[Teleton]

Optimisation = wide grin when you get that ‘YES, moment, you sit back and enjoy the vinyl experience. I like how Marco describes his experience with the S c35C, Goldring G800 (years ago!) etc. That gives a newbie like me a level of confidence to post my questions.

[Stratmangler]

A dished recess in the mat shouldn't cause any playback issues, as most vinyl will self support.
It will minimise the record to platter contact, which may or may not be a good or bad thing, depending on your point of view.

Many records are not flat by design ;)

[Fergus]

Hi there and thanks for your interesting reply.

I think the last message from Stratmangler (haha nice moniker! Maybe I should be Telemangler) probably explains it.
I think the less contact there is, the more isolation form the platter there is.
So this would explain why some mats are dished or have those raised 'bits' that get slimmer towards the middle.

But I'm not very sure if that's the reason. Does anyone know for sure? I kinda doubt that they're designed so that warped records can be played with weights.

Fergus




Hi
Fergus, now that’s interesting. I see that the Sony designers also focused strongly on mat design. The ps4750 had a moon mat, did those circles have some suction effect? This would be a design consideration to prevent record movement, very different solution to a clamp/weight solution. Then I see the top Sony mat was the oil filled one, and Sony actually say to reduce vibration! No dishing effect on Sony mats!?

So I’m seeing 2 requirements- 1. Prevent vinyl slippage and 2. Reduce vibration.

Anymore requirements a mat should meet?

Maybe a space undeneath as you have observed Fergus, but why?

[karma67]

...also Oyaide must have researched the best azimuth angle for their mats other than 90 degrees. I guess we are truly into the ‘art’ of vinyl replay here. I can alter azimuth with one of my head shells to experiment.

There is no better azimuth than 90 degrees

[Teleton]

Thank you Jamie, this is my thought too.

I see that Jvc, and Yamaha designed an electronic mat air suction device on their top decks. Wow such elaborate design, Sony too?