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Jypres raises some good questions about wood stability. Questions that we have given a lot of thought. We have done a lot to minimize the risks but wood stability is a tricky thing. The bottom line is there will always be at least some risk no matter what we do.

We rely on a number of techniques for stabilization of the platters. Each technique by itself would probably be inadequate but combined we believe the risk to be very low.

Our primary vapor barrier is formed when the core of the platter is assembled. Many small pieces of wood are saturated in epoxy and then joined under light pressure, leaving an effective vapor barrier between each piece. This is a much more effective barrier than can be obtained with a relatively thin finish. Once the core of the platter has been formed it is completely encased with a layer of cocbolo. The veneer is attached with epoxy to form an additional vapor barrier. We top this off with an epoxy coating. The exterior epoxy coating is fairly effective, but by itself would be inadequate.

Even with the above techniques, some limited moisture exchange is inevitable. Using many small pieces of wood with strong epoxy bonds minimizes movement. The dimensional changes in small piece of wood are small enough that the force can usually be contained by a strong bond. It's what we see with plywood. The bond between thin layers is sufficient to stabilize wood even with significant moisture exchange.

In addition to using a lot of small pieces of wood we construct the platter to expand and contract gracefully. The grain of the core of the platter is oriented such that the inevitable microscopic dimensional changes will be uniform around the platters circumference. This way even if there is some change the platter will retain it's concentricity.

Last of all well selected Jatoba for construction of the platter core because it has a very low moisture/dimension coefficient.

Chris

TWL, Do you work for Teres or have some other vested interest here? Sorry but, your defensiveness to reasonable questioning of this issue leads me to question your motives.
I simply point out to others that they should carefully research the subject of wood stability on the internet and form their own opinion.
Notwithstanding your comments, average homes without humidity control are subject to very extreme variations in humidity, particularly here in the Northeast. Perhaps you live elsewhere. As a part time woodworker (I build 18th century reproductions), I am well acquainted with this problem, but as I said, don't take my word for it, just do your homework before investing. I'm sure Teres has done what they can to minimize this issue although I would still suggest they might think about treatment with PEG to replace all water content rather than just trying to seal wet wood.

Nope. Never had anything to do with Teres. Only own their turntable. And love it.

I use the Teres Cocobolo base. It is not sealed, other than a surface finish. Last time I looked, it was still on my shelf. Hadn't crawled off anywhere. I live in an area with over 90% humidity for much of the year. Smoky Mountain area. I have no air conditioning. I use a wood stove for heat. My TT is right near the glass door and is subjected to near freezing temps in the winter(when the stove goes out during the night), and over 90 degree temps in summer. Finish is still on, and stability is fine. It is not made nearly as stiff as the platter on the 340. I don't know what extremes you feel any TT is going to be subjected to, but I'm certainly right up near the max in that department.

I also work with wood. I make musical instruments, specifically acoustic guitars. I am keenly aware of wood stability characteristics too. I believe that a nearly 4" thick platter of puzzle-fitted hardwoods with a density so high that it will nearly sink in water, and then soaked in an epoxy treatment that is made to withstand permanent immersion in water, will do just fine in the home environment.

Now that you've questioned my motives, maybe I should question yours?

And let's look at the stability issue and its real implications. Let's say that it might even go out a few thou periodically under extreme conditions. What are the potential problems?
1) Let's say it goes out of round by a couple thou. Well the TT has a continuously monitored platter speed that is constantly being read by an optical sensor and feeding a microcontroller that maintains speed to less than a tenth of a percent continuously. Controller takes care of that. And yes, it reads the platter, not the motor.
2) Let's say it goes out of shape like a potato chip by a couple thou. Well, most records are at least a couple thou out anyway. The system handles those quite easily. No problem.
3) Let's say that it squeezes tighter on the bearing shaft. No problem, the bearing shaft is part of the spindle, and is not immersed in the bearing well at the section where the
platter is attached to the spindle. Can't affect anything there.

This is worst case. Please don't tell me that you think it is going to go out by inches.

And how about the many turntables which have MDF platters and bases? They don't change with temp and humidity conditions? How about aluminum? Doesn't it change with temp? How about steel? How about brass? They don't change? Of course they do. Do they change evenly? Maybe. Maybe not. Depends on if there were any stress risers in the material when it was made. That's why they cryo treat rifle barrels.

Yes, I think it is good that you make people aware of the characteristics of wood. As you say, buyer beware.

Jyprez

Wet wood? Are you familiar with the moisture content of the wood before it goes through the process that Teres uses? I know I'm not. I understand from reading the Teres web pages that there is some extensive cabinet making experience at their disposal. I doubt they are going into this blind, and I really doubt they would go to the expense and trouble of this process as just a marketing tool. Some exotic, space-age man-made material would fit that bill and without the headaches of possible future problems. As a part-time woodworker you should appreciate that the exotic woods that are being used here are not your average cherry, or oak, or maple, or mahogany, etc., that are used in furniture making. Teres has stipulated that movement is concern, but I agree with Teres that the movement in question here is much less than what we see with furniture.

Anyway, I would still love to hear the 365 or even the 235. But I fear that if I do I will never feel the same about my current TT.

Actually MDF will not change with temp and humidity. I once soaked a piece of MDF in water for days and could not measure the change with a micrometer. I can't speak for acrylic as I am not sufficiently familiar with the characteristics but perhaps a materials engineer out there can answer this.
You ask how many turntables have MDF bases. I would say a great many starting with the rega. How about speakers as well. Most all are made with MDF and a wood veneer. How many solid hardwood speakers do you know of?

As far as subtle changes in the wood. I am sure that teres has accounted for the most significant changes in their design. I certainly would not expect movement observable to the unaided eye or I would quickly ship my table back. But as you yourself have pointed out to all of us many times in this forum, turntables are exquisitly sensitive devices where tremendous differences in sound quality can be achieved with very subtle changes.
So let's see, should I play my records on a base with random and uneven density that is subject to even subtle expansion and contraction? For my part, I think not. But the ear is king so if it sounds better to you, then I say go for it!