MDF or Plywood for best sound in Hi-Fi rack ?

In my view the jury is still out on Maple butcherblock vs plywood, for the simple reason that I have not yet seen the results of any in depth experimentation with high quality plywood. There are some very interesting plywoods out there. For example, Finnish company UPM-Kymmene makes an extremely high grade Finnish Birch (not generic Baltic) product. The mechanically most stable type is the one rated for exterior, which can be recognize by the presence of thin black lines of glue between the layers of veneer. The thickest sheets normally imported in the US are 1 and 1/8 inch thick, but 2 inch thick sheets can be potentially sourced from the manufacturer in Finland. Blocks of the material are so stable that they can be precision machined and carved for prototyping of mechanical parts by tool&Die designers. I have experimentally worked on some samples. Progressive power sanding down to approx 3200 grit yields a highly polished seemless surface both on face and edge.

If I recall correctly, a 4ft x 8ft sheet of the max thickness costs $120. Such a sheet is made from 20 layers of extremely hard Finnish Birch veneer. Conversely, the same thickness sheets classified as Baltic Birch is made from approx 12 layers.

Constructing shelves or platforms by gluing 2 or three layers of such UPM Finnish material is likely to yield an amazingly stable surface, likely devoid of resonance at audible frequencies. Whether such a shelf is inferior or superior to a similarly thick maple butcherblock unit has of course to be demonstrated. It is worth pointing out that one of the reasons that Maple is used in platforms and shelvings is the romantic notion of its inherent musicality, as it is almost universally the choice material from which the solid wood back of the best violins, violas and cellos are constructed. However, in a musical instrument, the back is part of a mechanical sound amplifier, in which the wood needs to vibrate to generate music. Not so in our isolation platforms, which we want largely to sound as dead as doornails.

UPM Finnish plywood can be sourced in the US from

Plywood & Doors
866. 738. 7265
Speak to Rod.

Please note that minimum order is $300, which means 3 sheets. From three sheets you can build a sizeable number of shelves and platforms.

its mdf.

Guidocorona - “Not so in our isolation platforms, which we want largely to sound as dead as doornails.”

I cannot possibly disagree with you more.

Over a number of years, I have built a number of composite platforms to be as acousticly “dead as doornails” only to find that when placed under my turntables, the sound also becomes dead and lifeless. I used materials such as MDF, ply, aluminum, plexiglass and cork and got a few to be totally quiet even when rapped with a knuckle. The more dead the platform, the more dead the sound.

The plywood platforms I have tried (composite or no) have all produced a very vague thin sound.

Placed and a solid maple platform the sound is much more natural, detailed and lively. To my ears, no contest. I cannot explain why that is, but I surmise it is due to the fact that trees (and consequently the wood) evolved over millennia to withstand whatever nature threw at it, and now very capable of dealing with vibration and resonances. Maple seems especially capable of dealing with resonances within the audio frequency range.

I think your postulation as the maple acting as a “mechanical amplifier” in violins and as such not suitable for audio somewhat misplaced. While maple is used for the instruments you mention, I have yet to hear a more natural presentation from my turntable on maple than any other platform regardless of material.

Regards
Paul

BTW, if you do have a 18”x 15” of the plywood available, I would love to try it. I am not holding breath it will be better, but if I am wrong that would hardly be a bad thing for me.

Pauly, you have made some interesting experiments. Where your listening test blind tests?

Unfortunately I have only a small hand-sized sample of 1 inch thick UPM Finnish plywood. Not enough for true experimentation.

Here are some further thoughts:

If indeed the benefit of maple were transmissive rather than isolative, you may want to try a single large solid board, which we would expect to be more transmissive than a butcherblock, which is instead meant to break up vibrations and stresses to an extent. The back of string instruments is constructed from a single solid board, or two at the most.
You may also try to experiment with thin boards--one inch or even less, and see what the more flexible body has on sound.
After all, a company represented by Virtual Dynamics manufactures platforms and racks made from brass castings, that ring like church bells.

It is also worth pointing out that the original choice of maple by the old masters was partially a matter of necessity rather than of true exhaustive search. Maple being a rather common hard wood readily sourceable in most European sub-alpine and trans Alpine regions where luthiers resided and worked. At most, the wood was imported from neighbouring regions.
in the last few centuries, Luthiers having remained a conservative lot, never truly experimented too much with more exotic timber for their resonators.
Now days there are so many more very hard and relatively inexpensive woods to experiment with, even for 'isolation' platforms: Ype and Lyptus, just for example.
Have you ever tried to play with them?

Hi Guidocorono

No blind tests – blindfolds really do no work well when trying to queue a record. :-)

I never set out on experimenting to find/build the best platform. Rather my comments are based on things I have tried over many years. Obviously as time passes (and equipment changes) it is difficult to gauge which sounded better or worse. However, the terrible disappointment of spending weeks and $$ making a nice platform only to have it sound dull is difficult to forget.

I tried a 4” solid maple board under my turntable and it was noticeably better than a maple butcher block. I haven’t considered that thinner would be better, but it’s definitely worth looking into.

I am sure there are wood species better than maple, and of course not all maple are equal. I just happen to read some comments on the virtues of maple and decided to try it. The choice of butcher blocks rather than solid wood was mainly economical – a 18”x15”x3” butcher block cost me less than $75.

I find the idea of brass platforms interesting. Before I heard the solid maple platform I was toying with the idea of getting a 18”x15”x1” 6061-T4 aluminum plate and see what that sounds like. A number of turntable manufacturers are making platter out of metal, so there may be something in it.

Regards
Paul