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Goliath SR reads THREE ohms?!

Discussion in 'Amps and Cabs [BG]' started by jasonbraatz, Jul 29, 2002.


  1. jasonbraatz

    jasonbraatz

    Oct 18, 2000
    Oakland, CA
    after playing my normal rack thru my sr for a while at very low volumes for about 20 minutes, my poweramp shuts off - goes into protect mode. i look in my manual to see what would cause such a thing, and one of the causes is too low an ohm rating for the amp. i'm bridging mono so 4 ohms is as low as i go on the amp.


    puzzled, i check the ohm rating using my multimeter and it reads 3.0. i do the battery check and all the speakers are still functioning properly/wired up.


    WHAT THE HELL?!?!?!?!?! could someone with a goliath sr and a multimeter please check to see if theirs is the same way? (it damn well SHOULDN'T be otherwise i'm in trouble :( )
     
  2. Matthias

    Matthias

    May 30, 2000
    Vienna, Austria
    This is normal.
    The impedance of a cab changes with frequency, the given value (4Ohms in your case) is only 'nominal' impedance. The multimeter will always show a lower number than this.
    For further details see the 'amp-FAQ' by Joris.

    Matthias
     
  3. fast slapper

    fast slapper

    Dec 11, 2001
    Fresno, CA
    That's sort of strange. I didn't think that would be enough to put into protect mode. Never had any problems when my brother had a Goliath SR. I have heard that Carvin's don't do good bridged at 4 ohms. Is yours a older model?
     
  4. Hmm with your multimeter what you are measuring is DC resistance. The DC resistance is close to what the speaker is by about 1 ohm. So 3 ohms is fine. A speaker is inductance, impedance changes with frequency.

    :D:D

    Merls
     
  5. jasonbraatz

    jasonbraatz

    Oct 18, 2000
    Oakland, CA
    hrm...then why does my goliath jr read 4 ohms?



    is there any way around my amp deciding to shut off besides only running the cab off one side? the poweramp isn't even a year old.
     
  6. jobu3

    jobu3 Artist formerly known as Big Joe

    Feb 17, 2002
    Mountain Top, PA
    thats fine whenever you do an impedance reading on a speaker cabinet with a dmm it comes out as 3/4 of the actual reading hence the 3 for 4... perfectly safe!
     
  7. Gabu

    Gabu

    Jan 2, 2001
    Lake Elsinore, CA
    The power amp is still under warranty, so you might bring this up with Carvin.

    Also, you could try rocking back the volume on the power amp a bit. I assume you are diming it? Try 90%, then 80%... Perhaps you could find a level at which it won't overheat and shut down, then rock it back a little more for insurance.

    Like if it seems to work fine at 80%, use it at 75%. It's still 750 watts potential, which aint bad.
     
  8. boogiebass

    boogiebass

    Aug 16, 2000
    I drove my Sr. (Gawd, I wish I still had that thing) HARD with an SWR Bass 750. Never a whiff of a problem. Carvin amp, huh? Hmmm.
     
  9. jasonbraatz

    jasonbraatz

    Oct 18, 2000
    Oakland, CA
    the weird thing is that the amp wasn't even close to being warm!!! i was running the power amp at 1/3 and the preamp at about 1/4.

    so this is why it shut down (From the manual)
    i know that cable is good, but just to see i'll switch and play it some more today.


    and the bass750 goes down to 2.67 ohms, so of course you'd be fine there ;)


    so you guys think i should take this up with carvin, not swr? the cab is doing everything it should be doing?
     
  10. Gabu

    Gabu

    Jan 2, 2001
    Lake Elsinore, CA

    That is strange. I was thinking you had the power amp dimed and controlling your volume with the preamp. I would not expect your amp to overheat at your levels.


    That's a good idea too.

    How long does the setup work before the power amp shuts down?

    How long had it been working normally before then?

    Is the time it takes to fail fairly consistent, or does that fluctuate widely?

    My initial guess is that you should take it up with Carvin. But I guess if your cable was a bit flaky, maybe it does intermittently short. But then it should be at seemingly random intervals. (Because it would probably be shorting when just the right vibration hit it.)
     
  11. LiquidMidnight

    LiquidMidnight

    Dec 25, 2000
    Yeah, you might want to drop Dr.Sound, over at Carvin, and e-mail. He might be able to figure out what's going on.
     
  12. fast slapper

    fast slapper

    Dec 11, 2001
    Fresno, CA


    That's the same setup my brother had. Too bad he sold it. :(
     
  13. boogiebass

    boogiebass

    Aug 16, 2000
    Shouldn't matter. Any amp capable of driving a 4 ohm load should be fine with the Sr. Sounds like that Carvin power amp is the problem to me.
     
  14. jasonbraatz

    jasonbraatz

    Oct 18, 2000
    Oakland, CA
    right. well it must have been a shorted speaker cable, because i changed it and it's been on for a while and hasn't done anything out of the ordinary yet. (besides sound great and be super loud)


    we'll see how it does at my upcoming gigs and rehearsals and i'll post a thorough review in a week or so.
     
  15. farboozle

    farboozle

    Apr 18, 2000
    Fairfax VA
    Good . . . cause its a shame everyone immediately brought up the doubt that Carvin runs bridged into 4 ohms. I run mine bridged into 2 8 ohm cabs all the time, hours and hours, with no problems.
     
  16. 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
    Gain controls don't limit the amp's maximum output power capability. If you turn down the gain, the amp just requires a hotter input signal to reach full power.