Compare JCM800 & JCM 900 Cabs?

Discussion in 'Amps and Cabs' started by JWR, Jan 9, 2008.

  1. JWR

    JWR Member

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    Curious if anyone has compared the two straight cabs, side by side, (with the same 4 speakers) and if there was anytonal difference between the JCM800 cabinets and the JCM900 cabinets. Construction appears to be about the same, I'm assuming older is mo' betta.
     
  2. JamesHealey

    JamesHealey Member

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    im pretty sure nothing much changed in the cabs from 800 to 900.. but the 70s basketweave cabs are noticably better.
     
  3. John Phillips

    John Phillips Member

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    I think the JCM800s sound better, but it may be because the 900s have that crappy, unreliable and probably tone-blocking PCB switching panel. 800s just have a single jack.

    There's also a difference in wiring even when the 900 is run at 16 ohms - it's wired series-parallel, whereas the 800 is wired (like all older 16-ohm Marshall cabs) parallel-series. This alone could explain most of the difference.

    But the 900s also seem a bit lighter, so I'm not convinced there isn't a woodwork difference too (and I haven't weighed them, to be fair).

    The 900s sound thinner and more 'hollow' to me.
     
  4. JamesHealey

    JamesHealey Member

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    whats the difference between series-parallel and parallel-series?
     
  5. ToneGrail

    ToneGrail Member

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    Actually, I think that the 900's are a little heavier due (to more particle board components?). I have 2 800 cabs and my friend has a 900 cab.
     
  6. John Phillips

    John Phillips Member

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    Series-parallel - two parallel pairs wired in series. This gives higher damping because each speaker is paired with another in parallel, and has a more 'parallel' sound overall, which is typically clearer and less midrangy.

    Parallel-series - two series pairs wired in parallel. Lower damping and more speaker-characteristic reinforcement because each speaker is in series with another and more indirectly in parallel with the other two - more of a 'series' sound, which is typically richer and more complex.

    The amount of particle-board components should be the same - just the back.

    It is actually possible that they're the same weight (or vary randomly a bit) and I'm just imagining that the 800s are heavier :). Really old ones are definitely heavier though, and have no particle-board at all.
     
  7. JamesHealey

    JamesHealey Member

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    just took out the PCB and re-wired to Parallel-Series..

    Tone improvement, didn't cost a penny either. recommend.
     
  8. zzmoore

    zzmoore Member

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    "All else being equal", can you hear the difference and be able to say which one was wired which way?
     
  9. John Phillips

    John Phillips Member

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    Yes, I think you can, if you're familiar with the particular cabinet and speaker type. It's a smaller difference than either of those though, and also smaller than the difference between running at 4 ohms (parallel) vs 16 ohms (series) with the same speakers.
     
  10. zzmoore

    zzmoore Member

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    Thanks for the info Mr. Phillips. We have three 4x12 cabs. Just took a peek under the hoods. Without even thinking about it (or knowing the difference) I have wired all three parallel from the jack and then series speaker to speaker if I am saying it correctly.

    JWR - Apologize for "butting in" on your post. It kind of happens a lot when John Phillips, KCA tubes, and other guys like that get involved.
     
  11. ChickenLover

    ChickenLover Member

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    I actually measured my 900 cab (with that switching PCB in there) and often I would get an open...but the cab always worked. One day I pulled out the PCB and the contacts on that switch were so grungy/dirty that it was no wonder why I got intermittent opens when measuring it. Removed it and just installed jacks..but I also replaced speakers at that time so can't comment on the tone-sucking...but crappy/unreliable I believe and agree 100%.
     

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