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Changing ohmage by rewiring cabs...

Discussion in 'Amps and Cabs [BG]' started by Audiosolace, Mar 26, 2003.


  1. Audiosolace

    Audiosolace Guest

    Oct 8, 2002
    Knoxville, TN
    I know this is possible for guitar cabs, but is it possible for bass cabs? Here's the situation:

    My rig consists of a 1x15" cab and a 4x10" cab, each rated at 8 ohms. My amp is rated at 350 watts/side into 8 ohms and 625 watts/side into 4 ohms. Does anyone know if there is a way to wire the cabs so that my new amp can perform to its full potential? Any help anyone can offer would be very much appreciated!
     
  2. The 4x10 cab is probably wired in series/parallel. The 2 pairs wired in series (16 ohms each) then in parallel dropping it to 8. You could wire it in all series making it 32ohms:meh: or in all parallel making it 2 ohms which really isn't much help. As for you single 15 that is an 8 ohm? Your pretty much stuck with it. Can you Bridge you amp? If it will bridge into 4 ohms then you could hook both cabs in parallel have something like 1200 watts.
     
  3. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    Can the amp be bridged? Will it drive a 4-ohm load in bridged mono?

    If so, put the amp in bridged mono, and connect the two speaker cabinets in parallel to make a 4-ohm load.
     
  4. Audiosolace

    Audiosolace Guest

    Oct 8, 2002
    Knoxville, TN
    If I had two full-range cabs, I would definitely run mono-bridged. I think running my amp mono-bridged disables the amp's onboard crossover, though. If anyone has any suggestions that might help me get more power to each speaker, I would love to know!

    :bassist: For now, I guess I'll just have to live with underpowering my monstrous rig until I can afford to upgrade from Avatar to Aguilar!
     
  5. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    You're biamping a 1×15 and a 4×10?
     
  6. What amp head are you using?
     
  7. Audiosolace

    Audiosolace Guest

    Oct 8, 2002
    Knoxville, TN
    I'm running an Ampeg SVT4 Pro.
     
  8. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    FYI, the term ohmage doesn't exist.
    It's <b>impedance</b>.
     
  9. Audiosolace

    Audiosolace Guest

    Oct 8, 2002
    Knoxville, TN
    I know that, man, but impedence just sounds so... passe! :D
     
  10. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    Well it is - it's imped<B>a</b>nce. ;)
     
  11. Audiosolace

    Audiosolace Guest

    Oct 8, 2002
    Knoxville, TN
    :meh: :confused: :rolleyes: :eek:

    Let's not change the subject!
     
  12. If you're bi-amping and want to change the impedance of your cabs by re-wiring them, your probably wasting you time. You can run them both full range and bridge your SVT Pro4. I just read it in the manual. This would give you full power.
     
  13. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    OK, like Greybeard said, you're pretty much stuck to running one cab per side.

    The bridge option he mentioned won't work, since the amp is rated @ 4 Ohm minimum load (and not 2 Ohm), bridge mode is @ 8 Ohm only.

    But 700W (350W per cab) should be sufficient, unless the cabs are superquiet.
     
  14. Audiosolace

    Audiosolace Guest

    Oct 8, 2002
    Knoxville, TN
    I'll play with it some more tonight and see what kind of sounds I can get out of it. Thanks for your help everyone (except JMX who did nothing more than give me a headache)! :cool:
     
  15. :confused:
    Technical Specifications
    OUTPUT POWER RATING 1600 Watts Mono-Bridged @ 4 Ohms (1200 Watts Continuous)
    1200 Watts Mono-Bridged @ 8 Ohms (900 Watts Continuous)
    2 x 900 Watts @ 2 Ohms (600 Watts Continuous)
    2 x 625 Watts @ 4 Ohms (490 Watts Continuous)
    2 x 350 Watts @ 8 Ohms (300 Watts Continuous)
    SVT-4 PRO Bass Amplifier (copied directly from the manual at the website.)
    www.ampeg.com
     
  16. redneck2wild

    redneck2wild

    Nov 27, 2002
    Memphis, TN
    Do you need more volume than you are currently getting?
    Is it overall Volume you need or just louder in certain frequencies (such as more Punch or more Lows)?

    Many people that biamp do so to get louder Lows without sacrificing the clarity of the Mids and Highs.
    If it is more Lows you are after, you may try lowering the crossover frequency and boosting the Lows and Low Mids. Lets say that you crossover at 50hz. If the 4x10 is a full range cabinet it should be able to handle 50hz and up without being muddy. The 15 would then handle 50hz and down and the Lows could be boosted.

    Some 15s don't work very well as full range cabinets. They tend to be very "Honky" in the Mid range area. If you run both cabinets Full range, you may have to cut the Mids to get the same sound you have when Biamping.

    Boosting Midrange frequencies may give you an overall volume increase (as Mid frequecies don't eat as much power as Low frequencies). Sometimes Mid frequencies get lost though as they are in the same range that Guitarists lows are in. Some guitarists will even turn up the volume if they think the bass is cutting into their frequency range. This happens particularly in Metal groups with 2 guitars.
     
  17. Audiosolace

    Audiosolace Guest

    Oct 8, 2002
    Knoxville, TN
    Thanks for the specs GreyBeard, but I actually have the manual (managed to score the amp brand new for $430 on a trade-in at GC). The main reason I'm looking to run the amp at 4 ohms is so that I'll be able to turn up without pushing the amp's limiter circuit into kicking on.

    You make some good points too, redneck2wild! I don't necessarily need more volume, its just that as it stands I'm running the amp wide open and getting just enough signal to cut through my guitarists 4x12" Legacy cab. I really just need to play more with the tone shaping options - of which this amp has a myriad!

    And JMX - I retract my previous statement. After a handful of Ibuprofen and a redeeming post, my headache officially be gone now. Want another reason why TalkBass is the best bass related site ever? I haven't even left work yet and I've already gotten all the answers and ideas I needed... and then some! Thanks again, guys!
     
  18. JMX

    JMX Vorsprung durch Technik

    Sep 4, 2000
    Cologne, Germany
    Thanks from the info Greybeard.
    From your first post I'd gathered that the amp runs @ 4 Ohm minimum load.
    Ok course with birdge mode @ 4 Ohm it's possible.
    Whether it's reliable at that load is another matter though.
     
  19. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    If the minimum load per channel is 4 ohms, then the minimum load in bridged mono is 8 ohms.
     
  20. redneck2wild is probably right when he says that it's your tone that is getting barried by the guitars. From the way you describe things, you have a 1x15 and 4x10 cab biamped with your SVT Pro. You're bi-amping it and still don't have enough power. Without knowing how the rest of the band is setup it is hard to speculate about settings. Howmany guitars are you competing with? Are you going through the PA as well? Is it that YOU can't hear yourself or is it that you're not being heard out front? I would think that with a rig like you have and the power it commands that you must have your tone set way too bottom heavy which is soaking up all your power without really producing a lot of audible sound. Good luck:bassist: