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Speaker testing in an old SVT 8x10

Discussion in 'Amps and Cabs [BG]' started by rojo412, Mar 4, 2003.

  1. rojo412

    rojo412 Walnut is fun! Supporting Member

    Feb 26, 2000
    Cleveland, OH.
    Okay, I have the duty of "offing" this refrigerator sized cab from my guitarist's basement. He used to be a bass guy, but long since abandoned his big rig for a smaller, manageable one. He wants the cab gone and he wants money.

    Well, I don't want the thing. It's bigger than my car and proabably sounds just as good plugged in. ANYWAY, he said it has busted speakers. He doesn't know how many. So I came up with a plan:
    Remove the speakers and test them to see which work, sell the workers, sell the busted ones super cheap, sell the badge, cloth, etc, then try to get the cab dragged out so someone can rebuild it (or live in it, whatever).

    How should I test the speakers? There's the battery trick, but I don't quite know the specifics of what needs to be heard. I also have a workingman's 1x10 and could plug them each in and see what's up, but ohmwise they are odd. Would a 32ohm speaker be damaged/damage an 8 ohm output? Logic says no, but what do pros say?

  2. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    The 8 ohm output of your WM10 is the minimum load impedance. You won't do any harm in connecting a 32 ohm speaker...you just won't get much power out of the amp.

    You might want to measure each voice coil's dc resistance with an ohmmeter. That will give you a rough idea of the individual driver's impedance.

    FWIW, the dc resistance will be close to and slightly below the speaker's impedance.

    The battery test will only tell you if the voice coil is open or not...it won't show a rubbing voice coil, etc. Only an actual playing test will do that.

    I'd recommend that you test each speaker in the WM10's enclosure. It should give you a lot better idea about each speaker's health.

    Have fun!!!
  3. rojo412

    rojo412 Walnut is fun! Supporting Member

    Feb 26, 2000
    Cleveland, OH.
    I just bought a multimeter from Radio Shack, 18 mode. You wouldn't know what function it should be on, do you? It has various resistance settings. I should probably read the instructions.

    I was basically double checking on the ohm thing, but if you know what the speakers are rated at, that's my major concern (don't want to blow them by testing them). I've opened up stuff before to find no markings to let me know of what the power handling OR ohms would be.

    And what are vintage Ampeg speakers raw worth on the open market?

    Other idea I had was to use what does work to make a 3x10 cabinet. Are there sorces on the net that describe how to wire 3 32ohm speakers to produce 8ohm resistance? How about a 3x10 with a horn/tweeter?
  4. Set your meter for Resistance (R) range slightly over 32. It will probably have to be 200. You should read about 24 ohms resistance for a 32 ohm impedance speaker.

    To make an 8 ohm cab, you'll need (4) of them hooked in parallel.

    To repay me for my help, you can send me the Ampeg Logo off the cab. I need one for my B25B cab. :D

  5. rojo412

    rojo412 Walnut is fun! Supporting Member

    Feb 26, 2000
    Cleveland, OH.
    I'm putting it on ebay when I get it. Like I said, this is not my gear. If it doesn't sell, it's all yours!

    I think I'm gonna scrap the 3x10 idea... building the cab is not something I could do without the tools, but I would love to wire it.

    Thanks for the help!