that whole "particle board vs. BB plywood for a 4x12" back" thing...

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by SeanF, Jan 1, 2015.

  1. SeanF

    SeanF Member

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    I just happen to have a Marshall slant cab loaded with G12-65's here, and it has a particle-board back, so I built a BB plywood back and ran small-signal tests on both of them. I'm not sure what the results really are, maybe you can figure it out. The green line is the BB plywood, the purple is the original back. The test was run with the Dayton Audio Test System, which measures impedance, not the actual sound level coming out of the cab, so that kind of complicates things, but I thought it was interesting anyway. To me, it sort of looks like the BB plywood enhanced the bass and cut the lower mids a bit, which correlates with what I and the owner are hearing; a bit more definition, and a little stronger bass. Still, it's not a huge difference, which makes sense, as both backs are under tension from the center brace. I inadvertently cut off the units on the X axis, but it's Hz, and the resonant peak is just above 100 Hz in both cases, so you can kind of go from there.

    [​IMG]
     
  2. TimmyP

    TimmyP Member

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    If it were a hi-fi or PA cabinet I'd worry about measurements. Being that it's a guitar cab, just use the one that you prefer when your guitar is blasting through it.
     
  3. pdf64

    pdf64 Member

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    Different cabs will generally give different (to some degree) results, even when built using the same materials / dimensions / drivers.
    Bear in mind that the TS characteristics of Celestion guitar drivers aren't specified
    For the test to be useful, it would be beneficial to provide results of the same cab with different back panel materials.
     
  4. SeanF

    SeanF Member

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    that's what I did; same cab, speakers, everything, just swapped the original back for a BB plywood back. Not sure why the picture doesn't show up, but I can repost it.
     

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