I've tried out some various things on my turntable to improve sound quality that I want to pass along.
There are some considerations that led me to my "special sandwich":
1. The Meitner turntable, which clamped the LP at the label (top and bottom) and suspended the grooved part of the LP unsupported. Meitner's idea was to let LP resonances radiate harmlessly into the air. I wondered how I might achieve something simlar.
2a. The Extreme Audio None-Felt mat.The online pictures look like it's made from a synthetic rubber mesh. I thought it might function similarly to the Meitner platter by creating a mostly air layer between the LP and the platter.
2b. In an earlier thread I posted asking about mats, one respondent mentioned using some of that polypropylene shelf and drawer liner. It seemed that the material was similar to what's used in the None-Felt, but of course doesn't cost $40 per square foot.
3. In Funk Firm's AchroMat, Funk Firm claims that the Achro's effectiveness is because the material "provides a perfect acoustical/mechanical impedance match to the vinyl of the LP." Funk Firm also mentions that putting a lot of air bubbles into the mat is part of the reason it works so well. It made me wonder if the "air mat" aspect of the shelf liner couldn't accomplish the same thing?
Concerning my needs in a turntable mat, my requirements are:
1. Something that REALLY dampens my rings-like-a-bell aluminum Technics platter.The bottom of the mat must quell as much ringing as possible. If your TT has an MDF, plexiglass, or glass platter, this is less of a problem.
2. Something that drains the resonances of the LP without overdamping it.
3. Something that provides traction almost to the point of stickiness so that leading transients are preserved, thereby avoiding weakened rhythm and pacing.
Well, here's what I came up with. It's cheap almost to the point of being free. It bears further experimentation but it's worth passing on.
1. I use the supplied DJ felt mat on the bottom because it's not too thick, yet it quiets the platter ringing significantly--possibly better than the stock rubber mat.
2. For a "perfect mechanical impedance match to the LP," why not use...another LP? I pulled out a thick LP from a Reader's Digest boxed set that I will NEVER miss, and placed it on top of the felt mat.
3. To provide air and traction, I bought a 12" x 5' roll of polypropylene shelf/drawer liner from Walgreen's for $1. Something like this
. I traced the Reader's Digest LP onto the poly mesh with a Sharpie. Don't forget to mark the center hole.
To summarize, I place the felt mat on the bare platter to damp it, a thick LP on top of this to provide a "perfect mechanical impedance match" to the LP, and lastly the polypropylene mesh mat to support the record.
This poly mesh layer performs THREE tasks very well: its mostly air layer isolates the LP from mechanical vibration from the turntable, it allows the vibrations from the playing LP to radiate into free air, and it provides a boxload of traction. Any LP vibrations that get past the poly layer would (presumably) get absorbed by the Reader's Digest LP which is then damped by the felt mat underneath it. A Sorbothane mat might even work better at that layer.
In fact, EVERYBODY should keep a 12" mat of poly mesh handy. Any time you apply this as the top layer to any mat combo I've tried, it imparts a most compelling rhythm and pace to the music. If you want people to dance to spinning vinyl, put'em on a poly mat. The jump factor it imparts is shocking (unless your mat already is as good at traction, I suppose).
How does this all sound? Clean, quiet, lively, and rhythmic. It gets rid of that ubiquitous upper bass resonance hump, improving inner detail. Rhythm and pace are livelier than I thought possible from LP.
Depending on the music and the mastering of a given LP, you *may* (or may not) want to add a clamp (lightly) or a 1-lb. center weight to clamp the LP. When I was playing an LP of Holst's "The Planets" it sounded a bit *too* light 'n' lively and the center weight brought it all into a nice perspective.
Right now, however, I'm using a variation on this. Recently I picked up a used Oracle Groove Isolator Sorbothane mat for $10 from the local Rega/Naim dealer.
On its own, the mat was very quiet; it's not annoyingly sticky like the Audioquest gel version. It's heavy and damps the platter amazingly well and adds a little more flywheel to the platter. But things sounded a little too polite and closed in. It was great for background music, not so good if you wanted some toe-tappin'. So I put the poly mesh on top of this and I REALLY like this combo. That Oracle Sorbothane mat damps the platter and quells resonances as no other, while the mesh top mat preserves initial transients and pace. And it works really well on every kind of music from solo voice or acoustical instrument to large scale bombastic orchestra.
If any of you have a Sorbothane mat collecting dust because it overdamps, go make yourself a poly mesh top layer for it and try it again. You may like what you hear. And you may want to try sticking an LP in between.