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Marshall JCM 800 cab wiring, paired with Montgomery-Ward

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  • Marshall JCM 800 cab wiring, paired with Montgomery-Ward

    Hi there,

    I've just rewired my 4x12 cab to become two 2x12s to accommodate for a new (old) Montgomery Ward head. One pair of speakers is playing loud and clear, the other side sounds extremely underpowered. One speaker at maybe 60%, the other at maybe 25% of the expected volume (and compared to the other pair).

    I've tried this amp through another cab with two 8 ohm inputs and she works fine.

    The amp has two 8 ohm outputs, so I'm going from each into my "new" 2x12s (all the same speakers, celestion 16ohm wired in parallel for 8ohms). The "good" pair of speakers is wired to a regular mono phone jack. The "bad" pair is wired to a two-lead Cliff jack that was original to the cab.

    The contacts on the "bad" jack all seem to be tight, nothing visibly wrong. I've re-done the wiring once, cleaned up all the connections and triple-checked which wires go where... my only thinking is that maybe I have the poles wrong on my "bad" jack, since I can't find a schematic telling me which lead is which, I'm just going off of the pictures I took before I re-did the wiring (and maybe I've had the poles wrong for years and didn't know it).

    Could having my pos/negative incorrectly connected on my Cliff jack cause this problem? Or would I not be getting any sound at all?


    PS attached is a picture of the jack, if anyone can tell me with certainty which lead is which and whether or not this could be my issue

  • #2
    No picture is showing. On the cliff jack, closest to the nut is minus or ground.
    Make sure the speakers are in phase (plus to plus, minus to minus for parallel arrangement).
    "Everything is better with a tube. I have a customer with an all-tube pacemaker. His heartbeat is steady, reassuring and dependable, not like a modern heartbeat. And if it goes wrong he can fix it himself. You can't do that with SMD." - Mick Bailey


    • #3
      What g1 said. I'll add this: Plug a speaker cable into the jack and check the DCR at the other end of the cable. Compare the two sides. They should read slightly less than 8 ohms. If one reads something else, you know it's a wiring problem.
      "Yeah, well, you know, that's just, like, your opinion, man."


      • #4
        Another thought: Maybe one of your new speakers was damaged in shipping and the magnet let loose causing the gap to shift and bind up the voice coil. Check to see that the cones move freely on all speakers by carefully pushing on them with your fingers applying even pressure around the perimeter.
        "Yeah, well, you know, that's just, like, your opinion, man."


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