Compare JCM800 & JCM 900 Cabs?

JWR

Member
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444
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.
 

JamesHealey

Member
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746
im pretty sure nothing much changed in the cabs from 800 to 900.. but the 70s basketweave cabs are noticably better.
 

John Phillips

Member
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13,038
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.
 

ToneGrail

Member
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1,715
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).
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.
 

John Phillips

Member
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13,038
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.

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.
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.
 

JamesHealey

Member
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746
just took out the PCB and re-wired to Parallel-Series..

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

zzmoore

Member
Messages
7,183
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.
"All else being equal", can you hear the difference and be able to say which one was wired which way?
 

John Phillips

Member
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13,038
"All else being equal", can you hear the difference and be able to say which one was wired which way?
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.
 

zzmoore

Member
Messages
7,183
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.
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.
 

ChickenLover

Silver Supporting Member
Messages
1,965
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.
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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