2. tech-talk
  3. 1048228416

Why MDF so Bad???

Hi everyone,
I've been reading left and right about how bad MDF seems to be for equipement racks. Everyone seems to agree that MDF shelves will color the music badly. The only thing I wonder is why do many speaker companies use MDF in their speakers?

Also, does MDF sound bad in every thickness? Did someone try to use 1 inch thick MDF shelves?

I'm very curious about MDF so I'm getting a woodsmith to build a 5 shelf equipement rack made of 1 inch thick MDF (only 1 inch thick MDF will be used for the whole unit). The shelves will be fixed to the frame. The whole rack will be assembled using high strength glue only. No nails nor screws will be used. The rack will be veneered with 1/28" thick mahogany wood (no paper backing)... Also, the back of the rack will be reinforced by MDF braces... The overall rack will be as rigid as possible.

One more thing, the rack will sit on the same kind of spike Verity Audio uses on their Parsifal encores (I guess I want the rack construction to be as close to a speaker cabinet as possible)...

I'm getting this rack made as an experiment, not as my definitive rack.

Any opinions as to what I should expect from this rack (sonic qualities)?

I was also thinking to use some sound absorbing material under each shelves and on the inside of the sidewalls to try lowering sound reflection (am I off the track here?)...

One last question, any thoughts as to how I could improve this rack (please don't recommend to throw the rack out the window and get a brand name rack)?

If anyone is interested, I will be able to post some pics when the rack is ready...

Your input is greatly appreciated.

Thanks ahead
lgregoir
bob_bundus
1,834 posts
 
do you think I'm better putting the rack directly in the middle of the 2 speakers or leaving the rack a bit behind the speakers...
I would think that the rack placed somewhat behind the speakers is the more typical approach, but with the rear firing woofers you might find it works better otherwise. However when placed directly between speakers, staging may be degraded.
sean
6,231 posts
 
Karls: The tests that i've seen on speaker cabinets shows that going from .75" to 1.5" does reduce resonance and ringing, but not by what one would think. When one gets up to 2.25" to 3", the differences really come into play. As such, your idea about "super thick" shelves may have some validity but i'm not about to try it out myself : ) Personally, i've had much better luck with relatively low mass yet rigid wood that offers good internal damping. The shelves on the other "double thick" rack weighed something like 23 lbs apiece whereas my current shelves clock in at about 4 - 5 lbs each. The other rack also had the shelves acting as part of the support structure whereas these shelves are free-floating. I think that these are the two major differences in what i'm hearing / experiencing.

Lgregior: I basically agree with what Bob had to say. If you can get the rack behind the speakers, that would work much better than having it on the same plane. If you can get the rack far enough back so that the rear of both speakers is visible when looking from the side with no interference from the rack, you should be pretty good in terms of soundstage, imaging, etc... As far as the woofers pushing air / vibrating all of the gear situated behind them, that may be another story. Moving the rack to another part of the country might reduce this, but the cables would have to be awfully long : ) Sean
>
kidbilly
5 posts
 
Hello, I do not have a answer to your question, I have my own similar delimia. I too am in the process of buidling a rack using 1 1/8 MDF for shelves. It will be open on all sides (supported only at the corners) I also have 1" granite slabs that are to be placed on each shelf. Is this a good idea, are cones needed between the equipment and the granite for any benifets?
Thanks for any feedback.
crp's avatar
crp
38 posts
 
Lgregoir, I agree with Bob and Sean. I would not want my rack, or anything else, located within the soundstage (between and behind the speakers). So I would place the rack against the back wall at a minimum (acoustic difusion may help here?).

I built a rack with which I am quite pleased: The open framework is veneered plywood and oak. The shelves, which sit on points (cone set screws at four corners) are IKEA Lak shelves. This is a recipe posted by Caterham1700 a few months ago. These shelves are attractive black finish, light, stiff, damped, and cost $10 each. Search the archives for that thread.

As to the floor coupling, do you have a wood frame floor or a concrete slab?

Cheers
lgregoir OP
106 posts
 
I have a maple floor...
More to discover