I need help figuring out what is up with my bass cab

Discussion in 'Amps and Cabs [BG]' started by Chris Toy, Jun 13, 2019.

  1. Chris Toy

    Chris Toy

    Jun 13, 2019
    So I recently bought a used SWR Big Bertha 2x15. Long story short I plugged in a 300 watt 4ohm head to test it, and only got noise from the horn.

    Opened it up, 9 volt tested both 15" speakers, both are functioning.

    The wiring all seems intact and tight, what else can go wrong?

    Attached Files:

  2. two fingers

    two fingers Opinionated blowhard. But not mad about it. Inactive

    Feb 7, 2005
    Eastern NC USA
    Welcome to TalkBass!!!!

    Sorry you are dealing with this.

    The simplest thing to do when trouble shooting is to quickly determine what the problem is NOT.

    Try another bass, cable, head, speaker cable, etc. Even if you have to drag the cab to a friend's house or a local music store, remove everything else from your signal chain as a possibility.

    Hope we can help get this figured out.
  3. Chris Toy

    Chris Toy

    Jun 13, 2019
    I have tried with two basses, a different head,a speakon cable, as well as a 1/4" speaker cable, and have plugged the same heads into other cabs with no issue.
    two fingers likes this.
  4. two fingers

    two fingers Opinionated blowhard. But not mad about it. Inactive

    Feb 7, 2005
    Eastern NC USA
    We have some experts floating around here. I'm gonna tag one.

    @agedhorse you think you can help a new member out?
  5. bumperbass


    Jun 19, 2012
    What I found:
    Big Bertha's internal (passive) crossover divides the incoming signal into two frequency bands. The
    crossover point is 5 kHz (frequencies above 5 kHz are sent to the tweeter, frequencies below 5 kHz are
    sent to the 15" speakers).

    This is a 2-way crossover. There must be a problem with a solder joint. Most likely, my experience has been either a solder joint or a break in the wire of the coil feeding the two 15's.
    Look closer.
    Omega Monkey and Chris Toy like this.
  6. Stumbo

    Stumbo Guest

    Feb 11, 2008
    Try run the amp directly to the speakers bypassing the jack and internal wiring.
  7. One has to be suspicious of your 9v testing and how you determined good vs audio testing no good.
    Omega Monkey and Rabidhamster like this.
  8. bumperbass


    Jun 19, 2012
    To clarify, I mean a break in the coil's wire as it enters the circuit board.
    Chris Toy likes this.
  9. bumperbass


    Jun 19, 2012
    Yeah, but if he got ANYTHING from the battery, he'd get SOMETHING from the head if the speakers were good. Must be crossover.
    Omega Monkey and Chris Toy like this.
  10. Chris Toy

    Chris Toy

    Jun 13, 2019
    Thanks I'll be taking a closer look, it may be beyond my ability to attempt a repair. Probably just gonna take her into a shop.
  11. bumperbass


    Jun 19, 2012
    If you can solder, I think the board is held on by the jacks. You'll have to actually take it out to look at the other side. It's gotta be a connection. He||, send it to me.
  12. Pulverizor


    Jun 14, 2018
    New Zealand
    Try reflowing the solder on all the joints, no skill required lol, assuming you have an iron!
    LowActionHero likes this.
  13. Matthijs

    Matthijs Supporting Member

    Jul 3, 2006
    Maybe a stupid suggestion, but: did you check that fuse?

    Before taking a soldering iron to the crossover I’d bypass the crossover first and connect the amp directly to the speakers. That way you’d be sure the problem is in the xover. Although that probably is the most likely cause.
    Omega Monkey and Aqualung60 like this.
  14. john m

    john m Supporting Member

    Jan 15, 2006
    This is called the shotgun method.
    Not a good way to trouble shoot something.
    Omega Monkey likes this.
  15. bass40hz

    bass40hz Cigar smoker, scotch drinker, American Patriot Supporting Member

    Aug 13, 2014
    Richlands, NC
    I second the fuse check. I ran into a similar issue with a different brand cab, was going to replace the whole crossover for like $170 then I decided to check the fuse (aka "lamp") and...bingo...it was a $2 fix.
    Rock on.
    Last edited: Jun 14, 2019
    Omega Monkey and lizardking837 like this.
  16. Maybe someone monkeyed with the wiring and has the tweeter line going to the drivers and vice verse
    Omega Monkey likes this.
  17. moogieotter

    moogieotter Custom Title

    Jun 16, 2009
    Duluth, GA
    Big Bertha is a big ole girl....bouta buck - o - five.

    Love that cab. Hope it's an easy fix.
    Chris Toy likes this.
  18. BogeyBass

    BogeyBass Inactive

    Sep 14, 2010
    If speakers are fine.

    There is a connection issue with the board itself. Or connections at the speakers.

    Easy fix is remove dam thing wire jack directly to the speakers. Forget about the tweet
    thetragichero, scuzzy and Redbrangus like this.
  19. I second this
    scuzzy likes this.
  20. bumperbass


    Jun 19, 2012
    The fuse only protects the horn, and the horn works.