Anything wrong with using LDF (Low Density Fiber) boards for speakers

Discussion in 'Home Theater Projects' started by cacu, Jan 6, 2004.

  1. cacu

    cacu Stunt Coordinator

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    Went to local cabinet shop and he only carries LDF for his cabinets. It's really light. He says that it is as strong as MDF. So is there downside to using this stuff?
     
  2. Mattak

    Mattak Stunt Coordinator

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    As strong maybe, but as...dense...no [​IMG] Plywood is stronger than either, but strength isn't the factor you should be looking for. You can get MDF at any major home improvement store and many mom and pop places too. If you're having someone build a cabinet for you it shouldn't be any problem to have him work with MDF, other than that it might be a bit heavier.

    Fiberboard for cabinets...yuck [​IMG]
     
  3. ThomasW

    ThomasW Cinematographer

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    No form of fiberboard (LDF, MDF or HDF) is inherently 'strong'. Actually strength isn't the issue, it's high mass (weight) that's important when using fiberboard.

    For speaker cabinets use either 13 layer Baltic Birch ply or MDF/HDF....
     
  4. RichardHOS

    RichardHOS Second Unit

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    That doesn't make much sense, at least for low frequency enclosures where the natural frequencies of the enclosure are above the useable range of the subwoofer. In that case, you want high stiffness to keep the fundamental frequency high. For the same material stiffness and thickness, a more dense material will result in a lower fundamental frequency (panel mode) than the less dense material; therefore, all other things being equal, for sub enclosures the lighter material would be preferrable.

    However, my assumption is that LDF is quite a bit less stiff than MDF, despite what the cabinet maker may have stated about strength (which isn't directly related to stiffness anyway).

    In full-range and high frequency enclosures, things are quite a bit different. Keeping any resonant modes out of the speakers' operating ranges might be impossible, and in that case you want to minimize the amplitude response when a mode is excited. High mass materials work well for that purpose.
     
  5. cacu

    cacu Stunt Coordinator

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    Well, I regret asking a little too late since I already had it cut out and every ready to go. Now, the Eros design called for 1/2 inch plywood linning on the inside. I had it lined with 3/8 inch plywood. Would that be enough to make a difference or am I SOL? How about putting some damping spray from PE like Stinger Roadkill Damping spray? Would that help too? I'm trying to salvage the situation and not having to have it redone cuz it cost a lot of money to have the cabinet shop to do it.
     
  6. ThomasW

    ThomasW Cinematographer

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    You're building Wayne J's Eros MTM mini-tower?

    If so and the back is still open, laminate the inside with a layer of 1/4" Masonite. Then add double the number of internal braces. If the back isn't open add 4 times the recommend number of internal braces and hope for the best.

    No do not use the spray-on damping. That stuff isn't going to help when you've created a cabinet that's got less strength, less mass, and less rigidity than the design you're trying to copy.
     
  7. cacu

    cacu Stunt Coordinator

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    I can quadruple the number of internal braces. But Masonite, where can I get it? How to apply/laminate it to the internal?
     
  8. cacu

    cacu Stunt Coordinator

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    NM
     
  9. ThomasW

    ThomasW Cinematographer

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    4'X8' or 4'X4' or 2'X4' sheets of 1/4" Masonite are sold at any of the home center stores.

    You glue it on the same way you attached the ply. Use a adequate amount of TiteBond or similar wood glue.

    You'll need to use weights or brads to tack it in place until the glue dries. Make sure there are no air pockets/voids between it and the inner layer of LDF.
     
  10. cacu

    cacu Stunt Coordinator

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    Yes, I'm TRYING to build Wayne J's Eros. So actually the Masonite will be glued to the 3/8 inch Plywood which was glued to the LDF with titebond.

    Thanks for all your help.
     

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