TT on Symposium Super Segue - slate or maple underneath?

I've gotten a Super Segue for my VPI Avenger. I have various things on hand I can place under the Symposium. I wasn't sure if a 3" thick maple block would work better than a 1/2" thick piece of slate. The whole thing will be sitting on top of my wooden equipment rack. I know ideally I should try both to see what sounds better, but hauling a 70+ pound TT on and off shelves for listening tests (not to mention moving a 3" thick maple block around) can be a bit of a pain. I'm hoping someone here has had some experience with what they've felt works best under a Segue, so I could try that first.
I use a standard Segue platform under my turntable which sits on my Symposium Foundation rack.  I'm not sure that using wood under the Segue would be optimal in conjunction with the Symposium products as you may not realize the full potential of the coupling and dampening obtained with Symposium products used together.  I understand that Symposium recommends the Segue ISO platform specifically for turntables and I've pondered whether that would be provide any notable performance different over the standard Segue I use.  

Sorry that I don't have direct experience using maple under the Segue.
Thanks t_e_p. Unfortunately I don't have a Foundation rack, and the Segue will not fit comfortably on top of my old CWD rack (yes, I'll be moving to a better rack someday). I called Peter at Symposium and he suggested going Segue / slate / maple, but then I've been advised by others to skip the slate and go right to the wood. But I'm not sure what to do.
Seeing as you already have a wooden rack in the equation, try the Segue on the slate only.
Peter's advice is infinitely better than mine.  I've relied on his suggestions in the past which have worked out well, such as using an Ultra Platform under my tube amp.

@tonyptony: What you want is stiffness and non-resonance. An easy way to reduce resonance is to install constrained-layer damping (Green Glue, ASC Wall Damp, EAR IsoDamp) between two stiff (and possibly dissimilar; your 3" maple block and 1/2" piece of slate qualify) materials. You want stiffness for a couple of reasons; a particularly important one for a turntable is that the greater the stiffness of a platform (all else being equal), the higher it's resonant frequency. You want the support structure's resonance to be as far from (in this case above) the turntable suspension's resonant frequency (and that of the arm/cartridge) as possible. 

Geoff Kait recently here on Agon (in the thread entitled "Component vibration isolation question") provided a link to the tutorial on isolation by Shannon Dickson in a 1995 issue of Stereophile. Do yourself a huge favour and read it. In it you may find the answers to many if not all of your questions.

 In my opinion, never use slate the reflecting factor is extremely high and it performs poorly. Maple is a much better option.

@lak , do you think even if slate is used as part of a constrained layer solution? I've
It’s a longish story how to optimally place a turntable on an isolation stand. To make a long story short, the component on the iso stand should be placed on very hard cones AND the stand or anything under the stand should also be placed on very hard cones. This set-up strategy allows for minimum upward 🔝 transmission of “seismic type” vibration AND maximum downward transmission of any vibration on the stand itself, which can arise from the turntable motor, acoustic waves, etc. what you want to minimize is stored energy in the iso system.
Good question, I've not tried that. I'm sorry to say you will have to try it and judge for yourself. If I were to guess I'd say there is no benefit to using the slate as a layer and possibly a hindrance.

the component on the iso stand should be placed on very hard cones AND the stand or anything under the stand should also be placed on very hard cones.

@geoffkait, yes I can see that as being a logical approach. But the Symposium concept, if I understand it correctly, is to dissipate the energy transmitted from the TT / motor into the Symposium material solution,  mitigating the need to use hard cone materials to act as a direct drain for the vibrational energy into the contacted surface. It seems like a one vs the other approach - dissipation vs. directed coupling. If (IF) the couplers and pods act successfully to dissipate the energy from the TT before it hits a lower platform, I'm wondering now if that would be enough? I reread Shannon Dickson's Stereophile article (I had forgotten about it - thanks bdp24). His case seems to recommend pure isolation between the device and the lower supporting platform, through the use of a Vibraplane or similar. I know the bottom line is experimentation will be in order - I guess I was hoping to trim some options off the list to maybe make it easier.

But after years of being here, I'll admit Shannon and guys like you here with your background probably know a lot more about this stuff than me. :-)

The seismic energy is not totally eliminated by devices since they are mechanical filters. So, cones are desired to prevent energy from being stored in the system, whatever that system is. Does the Symposium deal with seismic vibration? Maybe it does, but they don’t seem to address seismic vibration, so who knows? It should, since seismic vibrations are worse for the sound than induced energy.  Seismic vibration in the range 8-12 Hz excite the Fn of the tonearm, cartridge and platter.  In any case, what is required for best results is a comprehensive program of mass-on-spring vibration isolation AND energy dissipation/damping.
Is thermal dissipation the same as storage?
It’s the opposite. 

Geoff, the Symposium system is a trio of their Rollerblocks under the turntable (which provides isolation in all planes but the vertical), sitting on top of their Segue shelf (which is an outer skin of stainless steel with a center layer of foam. My concern with the Segue is that I'm not sure the stainless steel is thick/stiff enough), the Segue having five springs on it's underside (there's your vertical isolation).

I'm going into Crosscut Hardwoods in Portland today, to look at their birch and maple plywood. They have it in 1/4, 3/6, 1/2, 3/4, and 1" sheets, in both 4' x 8' and 5' x 5', with plies numbering from 3 to 18 (depending on thickness). Cut into shelves, with two of them having constrained-layer damping between them, should make (with roller bearings) for a killer isolation platform. Stiffer, a higher resonant frequency, and more non-resonant than a simple maple block.

@bdp24 the Symposium Foundation, unlike the Symposium Osiris does not incorporate rollerblocks. I should know as I have an Osiris Ultimate for my main component rack (ARC Ref 6 preamp and Manley Steelhead) and two Foundations on either side for my two vintage tables, a modded/hotrodded TD124 and modded Garrard 301. The advice I received from some of the best minds in vintage tables is that direct vertical energy dissipation via the Foundation is superior to multiplanar energy dissipation. 

Right @fsonicsmith, the Symposium Segue (and Super Segue) don’t include a set of the Rollerblocks; the consumer must buy them separately and put them in place between table and Segue, or under a no-spring (presumably) Symposium platform.

My situation and needs are different, as my VPI Aries 1 has a separate motor pod, my HW-19 has a separate SAMA, and my Townshend Rock has it’s motor bolted onto that table’s Plaster-Of-Paris-filled "upside-down baking pan" plinth, which is very vibration resistant and non-resonant. My interest is in a support platform that is as stiff and non-resonant as possible, something I would think every turntable will benefit from.

At the hardwood shop I visited today, I checked out all the various thicknesses and number-of-plies plywood they stock. Remember the base Art Dudley made for his TD-124, which he wrote about and pictured in his Stereophile column a few years back? He chose Baltic Birch ply as his material, and the stuff is incredible! An 18mm thick sheet (just shy of 3/4") is 13-ply (the 1" version is 18-ply), each alternating ply grain-orientated 180 degrees to it’s two neighbors, with layers of glue joining all plies. The plies are void-free, and the resulting structure is extremely stiff and fairly non-resonant, the resonant frequency being relatively high, which is of course desirable, especially for a turntable (as well as CD players and tube electronics). With constrained-layer damping employed, it will be VERY non-resonant. I’ve done it with ASC WallDamp, which works great in this application (not to mention it’s intended use---between two layers of sheet rock in wall construction. Audiogon member folkfreak’s room was as so constructed, and his room is amazingly "quiet" (the walls are silent. You don’t realize how noisy walls are until you hear a room built using WallDamp.).

Baltic (Russian) Birch is available in both 5’ x 5’ and 4’ x 8’ sheets, and the 18mm thickness is priced at under $100 for either. A 4’ x 8’ sheet can be cut into twelve 24" by 16" pieces; twelve Baltic Birch shelves for less than the price of one 3" thick 22" x 16" maple block! Put two together with constrained-layer damping between them, and you have six shelves far superior in stiffness and non-resonance to a 3" thick maple block. I myself don’t want my shelves to have the sound or tonality of maple, I want them to have no sound at all. And that’s achievable!

By the way, the shop also had what is called maple (or walnut, and many other woods) ply, but all that is maple about that plywood are the two outer/surface layers, for looks. I actually like the look of birch; it’s modern in a Scandinavian/German kinda way.

Where's a good place to buy ASC WallDamp?

It's funny to see the resurgence of Baltic Birch. Dick Shahinian, bless his memory, knew how good such material can be for building speakers. Although IIRC he used Finland Birch, back in the days when I think the stuff actually came from Finland. I agree it's great stuff.

Tony, you can get WallDamp directly from ASC in Eugene Oregon, I believe. They (Acoustic Sciences Corp.) offers in in 4" squares, but also scrap pieces by the pound, trimmed pieces from end of rolls or installation jobs they do. I ordered some pieces years ago cut in the exact size (22" x 16") of the top (MDF) shelves of my Solid Steel racks, then bought extra top shelves to make doubled/constrained-layer damped shelves for the racks. I’m going to do it again, this time with Baltic Birch.

Speaking of Baltic Birch, I misspoke above when I said the plywood has each layer 180 degrees apposed in grain direction to it's two neighbors. That makes no sense! They are actually 90 degrees opposed, which of course greatly strengthens and stiffens the plywood, just what you want in a shelf or platform.