Adding cement / concrete to the interior of a subwoofer?

Discussion in 'Home Theater Projects' started by Javier_Huerta, Aug 22, 2003.

  1. Javier_Huerta

    Javier_Huerta Supporting Actor

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    Hi all,

    As I was looking through the designs of some friend who builds speakers, I noticed something weird on the inside.

    I asked him if that was cement. He said it was. It looked like plaster to me.

    I wonder. Does cement help dampen vibrations? Add mass so that the sub doesn't jump? Has anyone ever experimented with it? It looks like a cheap tweak.

    Thanks for any opnions!
     
  2. Greg_R

    Greg_R Screenwriter

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    Increasing mass is one method of dampening vibrations.

    The problem with adding cement to an existing design is that you will be changing the internal volume of the enclosure. It is important to keep this volume the same (your friend has already removed the space the cement consumes during his/her design phase).

    Working with cement is likely to cause problems (how do you attach it to the wood part of the enclosure, how do you prevent chips from bouncing around, etc.). However, I have seen some DIY designs that use cement-only enclosures (IIRC they used a cement pipe and cut the appropriate holes).

    A better tweak would be to add polyfil stuffing to an empty sub enclosure (lots of people do this to the Sony subs).
     
  3. ThomasW

    ThomasW Cinematographer

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    Ok here's the deal with speaker cabinets and mass/weight/density.

    As long as the Fs (resonant frquency) of the cabinet itself is out of the passband (operating frequencies) of the driver, it doesn't matter what the cab is made of as long as the walls don't flex. In other words; the Fs of the cab can be either higher or lower than the frequencies the driver is playing and everything will be fine.

    So thin and rigid (plywood) = high Fs, or thick and heavy (MDF, concrete, lead, whatever,) = low Fs. Either cab is fine. Neither is 'best'.
     
  4. ross ish

    ross ish Stunt Coordinator

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    My neighbor lines his cabinets with tile. The drawback is you need a fork lift to move it.
     

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