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Cab wiring idea--can this be done?

Discussion in 'Amps and Cabs [BG]' started by barebones, Jul 22, 2007.

  1. barebones

    barebones Supporting Member

    Jan 3, 2005
    Denver, CO
    My idea is to take a 4x10 cab and load it with 4 4ohm speakers. I would then like to be able to switch the cab on the back from 4 ohm mono operation (speakers wired series/parallel) to stereo operation, with each pair of 4 ohm speakers wired in parallel for 2 ohms per side. I know the speakers can be wired in either configuration, so my question is really about whether or not I can set it up to be switched back and forth as needed.

    Has anyone tried this? Any advice?


  2. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
    The simplest way I can think of is to wire the stereo configuration to a 4-conductor Speakon jack, then make two clearly labeled cables for the two configurations.

    Note: When I see 2 Ohms mentioned, it leads me to guess that you are thinking of going beyond 400 W. The speaker experts have pointed out that a single 10" driver can typically take no more than about 100 W before farting out.
  3. LesS


    Mar 3, 2006
    no longer a member
    Here is how I would do it:
    Wire each pair of speakers in parallel to a ¼ plug.
    This would give you one ¼ plug for each side, which would each be 2 ohms.
    For one ¼ inch plug lets call the wiring Left-plus and Left-minus.
    For the other ¼ inch plug lets call the wiring Right-plus and Right-minus.

    You would also need another ¼ inch plug for the mono hookup - lets call the wiring Mono-plus and Mono-minus

    Then you would need a DPDT switch, which has six terminals.
    (Radio Shack has at least four: #275-710, 275-1533, 275-653, and 275-636.)
    Numbered as you look at the switch from the bottom:
    1 - 4
    2 - 5
    3 – 6
    (1, 2, and 3 are left side; 4, 5,and 6, are the right side)

    Connect terminal 2 to Left-plus
    Connect terminal 3 to Mono-plus

    Connect terminal 5 to Left-minus
    Connect terminal 6 to Right-plus

    (Terminals 1 and 4 are not used)

    Connect Mono-minus directly to Right minus (no switch needed).

    Make a label to put close to the mono jack:

    “Each stereo jack is 2 ohms.
    Mono jack is 4 ohms.

    Before plugging amp into Mono jack:
    1) Unplug amp from both stereo jacks (Left and Right)
    2) Put switch on “ON” position.
    3) Then plug amp into Mono jack.

    Before plugging amp into Stereo jacks:
    1) Unplug amp from the Mono jack
    2) Put switch on “OFF” position.
    3) Then plug amp into the Stereo jacks.”

    When completed, as you look at the DPDT switch from the bottom (upside down) where the terminals are, the switch handle up will ON (the Mono 4 ohm mode) and the switch handle down or in the middle will be OFF (the Stereo 2 ohms per side mode).
  4. barebones

    barebones Supporting Member

    Jan 3, 2005
    Denver, CO

    Exactly the kind of info I needed, you guys--and fast, too! Thanks so much!

    I am wondering about the above quote. My thought was to use some neodymium speakers that supposedly have a higher wattage and Xmax than typical speakers. In the stereo configuration I would, I believe, have 600 watts per side with these speakers. My power amp puts out 900 watts per side into 2 ohms. Not sure if this sufficiently addresses the "farting out" issue or not. The goal here is not necessarily to go hog wild with volume, but to have the most headroom and be able to operate my power amp at maximum efficiency whether running mono or stereo. In other words, being able to have two 2 ohm loads for stereo operation, and one 4 ohm load for bridged operation, and all contained in one cab. Am I thinking this concept through correctly, or am I missing something?

    Another simpler idea I had, if this one proves to be flawed or impractical, is to just use two 2x10 cabs and wire each with a series/parallel switch, thereby giving myself two separate cabs that can be run at 2 or 8 ohms.

    Thanks again.

  5. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Long answer: Download WinISD Alpha Pro at linearteam.net, learn how to use it (they have a forum too) and you'll be able to answer your own question, at least as far as displacement limited power is concerned. Beyond that, all drivers suffer from thermal power compression in the voice coil, and the higher the driver rating the lower the percentage of that rating will it handle before power compression takes any additional input power and converts it to driver killing heat only, with no additional output resulting.

    Short answer: 900 watts into two tens won't get you any louder than 450 watts will.
  6. The stereo/mono thing in a 4 speaker cabinet is something marshall have been doing for quite a while, most guitar 4x12s are wired this way.

    Its just as bassist we see the pointless-ness of it, so we dont fall for it :p
  7. barebones

    barebones Supporting Member

    Jan 3, 2005
    Denver, CO

    Thanks, Bill. Although I don't understand all the technical ins and outs, this is exactly what I needed to know.

  8. barebones

    barebones Supporting Member

    Jan 3, 2005
    Denver, CO

    Well, one man's pointlessness is another man's... um, point... I guess...

    Er, something.

    Thanks everyone!


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