Marshall JCM800 series... HELP!!

Barefoot greg

Barefoot greg

Guest
Apr 24, 2016
109
28
4,551
33
#1
Hello, I'm new to the forum so I'd first like to say hello to every one! :):D:laugh::bassist:

And now to business haha.

I just picked up a Marshall JCM 800 bass series cab. It's the model 1510 with 4x10's.
The back plate states it's 200 watts @ 8 ohm's.
I got surfing the web lastnight looking for a head to run it and came across a lot of info on ohm's and watts.. I mean ALOTdrool which is good but it got to be a bit overwhelming. But very little info on these cabs:eyebrow:

One thing that I did find was that they originally came with Celestion GS10-50's.
I took the back the back off of the cab and found that it has four Carvin 10" speakers 200 watts @8ohms.

The wiring appears to just be Series(input jack wires to positive One of the top speakers, and negitive to the other top speaker, and wiring going speaker to speaker in a circle all the way around.) but I'm not ruling out the possibility it's hooked up wrong.

My electrical knowledge is intermediate so correct me if I'm wrong but the original speakers being 50 watts @ 8 ohm's each is why the original cab was labeled 200 watts @8 ohm's right???
50x4=200

So with the 4 Carvin speakers @ 200 watts @ 8 ohm's each had this cab been upgraded to 800 watts @ 8 ohm?!

Any and all info on these Marshall's, these Carvin speakers, this wiring would be greatly appreciated.

Thanks in Advance! -Greg-

P.S. Oh and I'll post pics once I know how :thumbsup:
 
#3
image.jpeg
 
#6
If that is the case with the wiring, with the speakers wired literally in a circular series circuit, yes your cab is now capable of handling a sine wave at 800 watts, but it is now 32 ohms! It won't take an 800 watt bass guitar signal though. Well, maybe an 800 watt amp full on at 32 ohms, haha.

Could we get a picture of the inside of the cab and wiring?

Secondly, the more ifo you can give about the speakers that are in there the better... Specific models would be good, and any TS specs... They may actually be a really bad choice for the cab. That's actually step 2... Let's confirm the wiring first.
 
#15
Well, I can't make it out 100%, but it actually looks as though someone who kinda knows their shizzle did some magic on that box. The wiring looks series-parallel, making the box 8 ohms. I can't necessarily imagine Marshall porting a cab with PVC, either. How does it sound?
 
#16
Haha you took the words right outta my mouth! I took a video showing everything inside it but had trouble uploading it, in which I showed the wiring drivers, and as I put it "super custom pvc porting so obviously somebody else had their hands in there besides the guys at Marshall" :D
 
#17
I've yet to get a give her a good test drive, i only played her a little bit and it was with a budget level Cort 4 string passive with j bass style pickups through a 50 watt 4 channel pa head, but even so I was very impressed with playing it how booming and thundering the sound was I played every simple bass line I could think of(12 bar Blues, walking bass, Yellow Ledbetter, Ironman, Money, pussy liquor, stand by me, how many more times, etc. etc. you get the point. I played scales and arpeggio's all up and down the neck and just played simple single note sustains all the way from low e to last fret on the g string, all of which sounded clear. I was looking for any reason to not drag the thing home but it did sound darn good.
 
#18
I don't have a bass amp head and my fender bxr 100combo amp's line out feature is meant to run straight into a pa board so it isn't powered and therefore can't run the cab. Not that I'd wanna use that long term but just until I got a amp head to run it. In researching lastnight I found info on ohm ratings trying to find the right amp head which got me started into individual speaker ratings and with the age of the cab I was antsy to get a peek inside. Only to find a whole 'nother can o worms as they say haha
 
#19
Here's a diagram that may help you see the wiring a little more clearly.
series-parallel1.png


As this cabinet has been modded with new drivers and ports the original documentation is pretty useless.

Hopefully whoever modded the cabinet modeled the speakers and tuned the ports for proper operation. I highly doubt the cabinet will take 800 watts of bass without bottoming out the drivers. Listen carefully as you turn the volume up, so you can find where the limits are.

Additionally if the rear panel does not have a screw in the middle it may rattle at higher volume levels. If you want to put a screw in, drill a pilot hole so you don't split the post.
 
Last edited:
#20
:smug:Okay my wiring looks just like this one in the diagram, other than its mirrored left to right and the tabs that the pos and negative terminals attach have the pos and neg on opposite sides due to the speakers being rotated 180 degrees. But that's not really important for this haha sorry I tend to give way too much info :woot: But both the wiring in the diagram and my cab are wired the same in the sense that the horizontal wiring for the top two speakers goes negative to positive, as does the wiring between the bottom two speakers. And the vertical wiring between the speakers goes Negative to Negative on one side and on the other side it's Positive to Positive.
The leads coming off the input jack run to Negative on one top speaker and to Positive on the other top speaker.
 
You must log in or register to reply here.
Top Bottom
Back