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Can I Convert my Cab from 8 to 4 ohms?

Discussion in 'Amps and Cabs [BG]' started by TheEmptyCell, Mar 17, 2009.


  1. TheEmptyCell

    TheEmptyCell Bearded Dingwall Enthusiast Banned

    I have a LDS 1x12" with a tweeter and small midrange driver. I ordered it as an 8 ohm cab, assuming I'd be getting another cab to stack it on. It's been a couple years, and I think I'm more likely to use it by itself or run my head at 2 ohms.

    I'm not sure what speakers are in it, but would I not be able to buy the same type of speaker or combination of speakers that would make it a 4 ohm load?

    Thanks for the help!
     
  2. Yes, changing the speakers is the only way to convert the cab from 8 to 4 ohms.
     
  3. Mikio

    Mikio

    Feb 21, 2009
    Santiago de Chile
    what's the difference between 8 and 4 ohms in sound?
     
  4. Bassamatic

    Bassamatic keepin' the beat since the 60's Supporting Member

    The sound wil be the same - 4 Ohms will allow the amp to deliver more power, but the audible difference will be very small.
     
  5. alexclaber

    alexclaber Commercial User

    Jun 19, 2001
    Brighton, UK
    Director - Barefaced Ltd
    And changing the woofer to 4 ohms will make the midrange and tweeter sound 3dB quieter. And even with a relatively low powered head most 8 ohm 12"s can handle full power without over-excursion so going to 4 ohms to get more power will be futile.

    Alex
     
  6. As has been pretty much said, the gains you make will be far outweighed by the cost. Put your money towards a second cabinet.

    Paul
     
  7. Adam Bomb

    Adam Bomb

    Mar 26, 2008
    Bezerkely, CA
    Let's talk about that for a sec. A 4-ohm cab will be louder, right? Not twice as loud, of course. But, if, say, you were *almost* loud enough in a situation with an 8-ohm cab, and the next time, everything was the same, except that now your cab was 4 ohms (and could handle the additional power), would you be like, "Cool, that put me over the top" or "Well that was a waste"?

    --Bomb :bassist:

    p.s. The geek answer - 3db or whatever - means nothing to me. I'm asking about the subjective experience of hearing, if that makes sense.
     
  8. hbarcat

    hbarcat Supporting Member

    Aug 24, 2006
    Rochelle, Illinois

    The 3db difference is the greatest theoretical difference but for practical reasons you won't see all that by switching speakers to go from 8 ohms to 4 ohms. To stay away from the geek terms and put this into real world languange, the difference in volume to your ears is likely to be right around the limits of audibility. Subjectively, it's tough to see how this is worth putting time and money into.

    Edit: Just curious why you need more volume. Are you playing shows and finding that you aren't able to keep up even with your amp running at full?
     
  9. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    If that. A lot of 4-ohm versions actually have reduced capabilities relative to their 8-ohm version. Even if they don't and have the same T-S specs, XMAX - useful excursion - will in reality allow them both to produce the same amount of volume before farting out or being damaged. Often that's like 1/4 or 1/3 of their so-called RMS rating.
     
  10. uaudio

    uaudio

    Apr 11, 2008
    Arizona
    I've never seen a clear answer to this question, because the topic always goes theoretical.

    If you have an amp capable of 350W at 8ohm and 550W at 4ohm, wouldn't swapping the drivers (in the same cabinet) increase perceived loudness because you can drive more wattage?
     
  11. herndonbassist

    herndonbassist Low Down Thumper Supporting Member

    Apr 7, 2005
    Herndon, VA - NoVa
    A good friend of mine swapped 4 10" speakers in his Ampeg cabinet in order to go from 8 to 4 ohms for just this purpose. In the end, he spent a TON of cash on the speakers, still had the old speakers, and felt that on stage, there was almost no discernable volume difference. Practically speaking, he went from having to turn up to 6 on stage with his power amp, to then turning up to 5 1/2 on stage with the swapped speakers. I hope that helps.
     
  12. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    Don't forget that you will need to buy or build a new crossover section for the woofer if you do this, assuming the cab has a full crossover to begin with.
     
  13. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Inconsequential.
    No, because most drivers won't accept more than half their rated power before farting out anyway. In most cases all you'll accomplish with going to 4 ohms is getting the driver to fart out with the amp's volume control a smidge lower than it takes with an 8 ohm load.
     
  14. olistorck

    olistorck

    Sep 16, 2007
    oviedo,spain
    I am amazed at the amount of crap being published here. Of course you can change from 8 to 4. For example with this: http://www.glockenklang.de/de/produkte/produkte_bass.htm
    A 4 Ohm cab is no way louder than an 8 ohm one. It is what the watts the amp delivers at 4 or 8 ohms that matters. Reconing speakers... cĀ“mon. You could rewire first to daisychain the total impedance, before spending tons of money. Simple electronics taught in 5th grade physics.
     
  15. uaudio

    uaudio

    Apr 11, 2008
    Arizona
    Is this the single most argued point on TalkBass? I am being totally serious - I can't understand how its possible that 500 watts at 4ohm isn't louder than 8ohm at 300.
     
  16. Passinwind

    Passinwind I know nothing. Commercial User

    Dec 3, 2003
    Columbia River Gorge, WA.
    Owner/Designer &Toaster Tech Passinwind Electronics
    Please enlighten us on how to do this with the single 12 cabinet the OP referenced.
     
  17. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    TRANSLATION: You didn't understand the good explanations from people who actually understand the thang.
     
  18. Tim1

    Tim1

    Sep 9, 2005
    New Zealand
    I played my Markbass into an SWR Goliath 3 410 8 ohms side by side with a Goliath 3 4ohms. The difference was virtually inaudible, certainly maximum attainable volume before the speakers started farting seemed the same, although the volume control could come down a tad on the 4 ohm version. I posted on this once and someone (I think it was JimmyM) made the point that while you may not notice the difference in volume it was more apparent in the extra available headroom at 4ohms, if for example you were slapping which requires more extreme dynamics. I seldom slap so could not comment on this.
     
  19. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    Said physics make it perfectly clear that even a multi-driver 8 ohm cab cannot be rewired to 4 ohms, let along a single driver cab. Unless you can figure out a way to strip wire from the voice-coil. :rollno:
     
  20. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    Did you actually read explanations and think about them? That's probably why you think you've never seen a clear answer to the question, as you said a couple posts back. If you are not capable of seeing, it doesn't matter how many decent pictures are drawn..

    But it boils down to this. If the speakers themselves can only make so much noise because of THEIR limitations, it doesn't help to try to force more wattage down their spindly little throats. They'll just gag on it, and could be damaged. So. Unless you have a pretty weak head/amp, going from its 8-ohm wattage rating to its 4-ohm wattage rating won't allow more sound. In most cases the speakers are the bottleneck.
     

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