1. Please take 30 seconds to register your free account to remove most ads, post topics, make friends, earn reward points at our store, and more!  
    TalkBass.com has been uniting the low end since 1998.  Join us! :)

How would I change the ohms on cabs (aside from rewiring or getting new speakers...)

Discussion in 'Amps and Cabs [BG]' started by addylewis, Aug 22, 2005.

  1. The Kustom cabs give out about 600 watts each, but they're also 8 ohms each, therefore if I needed the full 1200 watts I'd need 4 cabs right? (8 divided by 2 = 4 divided by 2 =2, right?)

    Is there a box or something that can change the impedence of the cabs? - 2 cabs should be enough, they'd give out 600 watts each...

    I'd rather not re-wire the things to do it - would soldering a resister to each side of a couple jacks from an old pedal do it if it were inserted between the amp and cabs?
  2. The type of idea you are suggesting would only make the amp run harder. It wouldn't provide more power to the speakers. Nothing short of new speakers will get you full power to your cabs. Rewiring won't work in your case either. :(
  3. Actually, they are rated to handle up to 600W each. So yes, if they're 8 ohm cabs, and the amp puts out 1200 W at 2 ohms, you'd need 4 8 ohm cabs to show 2 ohm load to the amp.

    Forget about using resistors to match the impedance. They will just take the extra power you get out of the amp and convert it to heat in the resistor, the power actually going to the speakers will not increase at all. So you get same power to the speakers with more strain on the amplifier.

    No sense making the amp work harder to put out more power if none of that extra power ever gets to the speakers.

    It's like the goal is to go faster, so you get a bigger engine, then you tow a car. You still don't go any faster, but you're burning way more gas, straining the car, etc. Worse than a waste of time, cause you get no more results, except more wear and tear on the equipment.

    the only way that make sense is rewiring the cabs, assuming its possible to end up with a 2 ohm load total when you're through. Depends on how the cabs are hooked up now, and what the impedance of the individual drivers is.

  4. Adding resistors to juggle the impedance to get more power out of the amp is like converting a $200 amp into a $400 amp by giving the salesman an extra $200 for it. You still end up with a $200 amp, but you manage to shell out $400 to get it.

    The extra power is wasted.

  5. cheers for the help guys

    yo Muzikman - why wouldn't re-wiring 2 cabs to halve the ohmage of them work? - surely it can be done with more wire, according to a diagram I've got it looks manageable anyway...

    I may just get one cab then upgrade the speakers if I need more volume... (that sounds a simpler solution dunnit? I'm crap at wiring anyway - thought my guitar was simple to customise till i plugged it in and it sounded like me touching the end of the jack lead with the amp on full distortion whenever I touched the strings!)
  6. Selta


    Feb 6, 2002
    Pacific Northwet
    Total fanboi of: Fractal Audio, AudiKinesis Cabs, Dingwall basses
    Last I checked, cabs don't "give out" any kind of wattage. They only handle so much thrown at them. If you want to take an easier road to 2 ohms, just get a single 4 ohm box. 8 ohm + 4 ohm = 2.66666 ohm load. Of course, then you'll have a volume difference to deal with :p. g'luck.

  7. Generally you can only rewire a cab to change the ohms by a factor of 4. Could be in either direction, depending on how they're wired now.

    So 8 ohm cab could go to 2 ohm, or to 32 ohms when rewired.

    2 ohm if its currently series and you go parallel, 32 if its parallel and you go series.

  8. Eric Moesle

    Eric Moesle

    Sep 21, 2001
    Columbus OH
    You can't change Ohms - its called "Ohm's Law" for a reason . . . . however, you CAN change the IMPEDANCE of a cab.

    I get dismayed every time I read the term "ohmage" on this board, which seems to have far surpassed the use of the proper term "impedance" by a longshot.

    Knowledge is power . . .
  9. (OK, its no secret that I messed up on my Physics 6 years ago at gcse...) :( :crying:
  10. Eric Moesle

    Eric Moesle

    Sep 21, 2001
    Columbus OH
    Not a blast at you, Addy. It seems to be just about the norm on the board. Just trying to educamate!!!!! ;)
  11. Yes, we seem to pay way too much homage to ohmage here....

    But since impedance is measured in ohms, you really can change the ohms of a multi-driver cab by rewiring the drivers... right? You're talking impedance ohm instead of resistive ohms, the symbol is Z and a vector quantity instead of R a scalar quantity, but the units are still ohms.

  12. Eric Moesle

    Eric Moesle

    Sep 21, 2001
    Columbus OH
    To quote an earlier clarification from Psycho Bass Guy:

    "The correct term is impedance which takes into account reactance and inductance in addition to resistance. A speaker is not a static resistance, hence it has impedance."
  13. Cool. You answered a question directed at me when I was away. :cool:
  14. Ok, I stand corrected.

    Hey, so what do they measure impedance in anyway? what are the units?

  15. Eric Moesle

    Eric Moesle

    Sep 21, 2001
    Columbus OH
    Apparently, here on Talkbass the units are called "ohmages" . . . though I would surmise that "ohmaginos" would be acceptable in the southern hemisphere . . .
  16. BillyB_from_LZ

    BillyB_from_LZ Supporting Member

    Sep 7, 2000
    I'm beginning to think that we worry far too much about running our amps at an impedance that will cause maximum power output.

    Since most amps that are capable of driving a 2 ohm load put out more than half their 2 ohm power at 4 ohms, the resulting volume difference won't be noticable to most of us anyway.

    Besides, if our half kilowatt + amps aren't loud enough, we should either plug into the PA (and blow up someone else's expensive equipment (oops, I own the PA too :eyebrow: )) or get the guitar players to turn down...

    Just my opinion...
  17. ESP-LTD


    Sep 9, 2001
    I thought folks spent most of their time worrying about what cabinet will 'put out the most watts'.

    Although ohmitude is important, I think wattishnicity has become the standard folks use.

    Curious, that folks don't want to discuss the transconductanceness of various preamp tubes; I reckon that's a guitar thing.
  18. I think this is a fair point.

    I would also add that when you go for max output, that usually means running the amp into its lowest rated impedance. Depending on the amp, it *may* not be at its best and most stable there (though some amps can run at their lowest rated impedance seemingly all day).
  19. just get another cheap 4 ohm cab 8+8=4+4=2 so now you have a two ohm load a full 1200 watts, And I bet it will all go to bedroom practice. look at the power your running now through two cabs. All running tat 1200 watts will give is mybe more headroom. but other than that it wont be a noticable change in volume. if you want to get louder you need more speaker space/cone area.
  20. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    These seemingly constant and incessant attempts at running as low an impedance load as posssible to get as loud as possible ignores a very important fact: most speakers are incapable of running undistorted at full input power. Or even half power, for that matter. Driver manufacturers learned long ago that the fastest road to bankruptcy is excessive warranty claims, so to circumvent that route they are in the habit of using voice coils that will withstand at least twice as much power as the suspension will. 90% of the time lowering the impedance load in and of itself is the audio equivalent of pissing into the wind. If you need it louder you either need a much larger amp or better/more sensitive speakers.