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

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

Each of you, back to your corners!

I would suggest mating dissimilar materials. Combine things with different resonant frequencies, thereby making it difficult for vibrations to penetrate the entire shelf.

The new Sota Cosmos armboard is made of layers of aluminum, carbon fiber, and plex. This is a good combination...

Anytime you employ one material, MDF or plywood, for shelving, you run the risk of exacerbating a resonant problem. MIX, MIX, MIX... The best racks use a mixture of materials...

:o

We layer our Signature Shelves... 19 times.

Nrchy is soooo right! Now if Sota only layered in useful things like Audiav does, it would sound good :)

In answer to your question: MDF for anti-resonance, Plywood for strength. Think low mass and viscous layers as alternates for layering. Or just buy a Signature Shelf :)

There are only a few materials that will gain a better inertness than MDF, but the cost goes through the roof.

I would tell you... but that would give away a few secrets.

A Granite decoupled layering sandwich works wonders... believe me :)