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Compressable Device In A Sealed Cab?

Discussion in 'Amps and Cabs [BG]' started by SurferJoe46, May 20, 2011.

  1. In automotives, we use accumulators in hydraulic circuits to take the shock out of a fluid pulse.

    Why not something like a bladder with air in it, inside the cab to take up the compression like a port would?

    Seems to me it would be an interesting experiment.
  2. ThrashMaster


    Jul 7, 2010
    Boston, MA
    passive radiator
  3. That would require an outside position - I'm thinking totally inside the cab.

    This bladder would be totally inside the cab and save a lot of cab-size that a passive would need.
  4. 1n3


    Sep 13, 2007
    Interesting idea, but I don't see how it would reduce cabinet size.

    Your bladder would have to be at a different air pressure than the rest of the cab to make a difference. I'm imagining a tire inner tube (with the valve stem sticking out the side of the cabinet :)). If you have the tube at above-atmospheric pressure, you have made part of the cabinet volume stiffer. That reduces effective cab volume - the opposite of what you want. If the tube has less than atmospheric pressure, it is collapsed, so does nothing.

    Perhaps others will see something I've missed.
  5. I'm thinking of a diaphragm about 1/2 of the whole cabinet volume that is neither positively or negatively pressurized to absorb the sonic wave and rebound it back to the cone of the driver - kinda like a very large 'sweet spot' in the resonance of the cabinet itself.

    This can make the cab much smaller and still be very LOW-freq able.

    A passive shock absorber that will re-propel the waves back out of itself - reinforcing the driver.
  6. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    Great. Instead of cone control, we'll be talking about bladder control.
  7. But you cab won't be affected by your prostate.

    Think about it.

    Win-win AFAISI
  8. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    What you're thinking of is basically to passively equalize the speaker.
  9. 1n3


    Sep 13, 2007
    If the air is at the same pressure on both sides of the diaphragm, I'd expect the diaphragm to be transparent to the speaker. But I guess that would depend on the mass and stiffness of the diaphragm. If those are significant, it starts to look like a passive radiator into a confined space. ? No idea...
  10. OK - well put -

    How about the diaphragm itself is resilient and sorta rubbery? That would be the 'spring-device' roughly equivalent to an accumulator.

    Except for losses to friction, an accumulator returns any energy that it absorbs, back to the source.

    Gotta be a way.
  11. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    The only way to passively equalize a speaker is to convert electrical power to heat.
  12. Go on........................ don't follow that in this case unless we want a combo that reproduces sound and cooks your food too.
  13. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    The air mass in a sealed cab already does just that. In a vented cab it would have the effect of removing internal volume, which would be counter-productive.
  14. Aha! Intelligence prevails again.

    Thanks BFM.

    But it was a good idea - no?

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