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Switchable speaker load.

Discussion in 'Amps and Cabs [BG]' started by rasrick, Mar 2, 2008.

  1. Has anyone ever had a bass cabinet that has a switch to change the load from ....let's say 4 ohms to 8 ohms when you want to?
  2. murphy


    May 5, 2004
    Toronto, Canada
    Don't open that can of worms.

  3. You cant switch a load from 4 to 8 ohms as far as im aware.

    If its a single speaker cab, cant switch anything

    If it has two speakers (say two 4 ohm speakers), you could switch between 2 ohms and 8 ohms

    Im not going into the higher numbers, but, basically, you cant do it while keeping all speakers active.

    What you could do is have a switch that removed some speakers from the circuit, but i dont think thats what your wanting to do.
  4. A 112 cab with a horn. I want to use it with a small practice amp that has an 8 ohm ext. output jack. and also use this same cab with a LM 250 or a Bassman 250/210. If it can't be done than OK I guess that's why my day job is in facility management. Didn't mean to open a can of worms. Just trying to be efficient with my dollars.
  5. anderbass


    Dec 20, 2005
    Phoenix. Az.
    You have no wiring options to change a single speakers ohm rating. You can only do this with multiple speaker cabs.
    (tweeters use a crossover and dont effect ohm ratings much)
  6. I have a 2x15" cabinet that I installed a switch on to go from 4 to 16 ohm. It's a series/parallel switch with two 8 ohm speakers.
  7. If you have an even number of speakers you can make the cabinet dual impedance just as Sean has done.

    I am embarrassed to admit that, back in the day, I did this to my Marshall 4x12 cabinet, 16&#937; when I was using my tube amp and 4&#937; for use with the new SS amps that were just starting to come in. Seemed like a good idea at the time until it dawned on me that my tube amp could be set to 4&#937; just as easily as it could to 16&#937;. After kicking myself around the room a few times I took the switch out and left the cabinet wired for 4&#937;. <Sigh> the follies of youth!

  8. murphy


    May 5, 2004
    Toronto, Canada
    The can of worms was the whole Accugroove fiasco.
    The accuswitch...4 to 8 ohm thing
    Turned out to be not real.
    So if you see old ads for that, just ignore it
  9. Mark Reccord

    Mark Reccord Supporting Member


    Great story! We've all done stuff like that, I know I have. :p

    You can make a cabinet switchable between 4 and 8 Ohms even with a single speaker, but it requires a big, heavy transformer in the cab. Not worth doing.
  10. crazyfish


    Sep 13, 2006
    Chicago, IL
    I'm no electrical engineer or anything, but isn't there a way to maybe wire a switch to be able to toggle an additional 4 ohm dummy load (a very high wattage resistor, for example) in series with a 4 ohm speaker? This seems pretty obvious to me but there's probably a lot of implications I'm not thinking of (maybe this is why cab companies haven't been doing it all along).
  11. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Burning off half the amp's output in the resistor is an implication.
  12. seamonkey


    Aug 6, 2004
    You can see the effect of adding series resistance here:
    It lowers the overall output, but also changes the frequency response.
  13. fdeck

    fdeck Supporting Member Commercial User

    Mar 20, 2004
    Madison WI
    HPF Technology LLC
  14. Kelly Lee

    Kelly Lee Yeah, I'm a guy! Supporting Member

    Feb 17, 2004
    Marana, AZ, USA
  15. The reason I wired up my 2x15 for series/parallel operation was so I could use my dad's 8-ohm tube amp with both my and his 16-ohm cabinets together in parallel, or use mine with a 4-ohm head.

    (As an aside, he thought before that his amp was wired for 16-ohm operation, so he wired his cabinet as a 16-ohm...2x8ohm series)
  16. Isn't that called "Dummy Emulation" :help:

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