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Joris...or any body else !!!

Discussion in 'Amps and Cabs [BG]' started by mikemulcahy, Feb 5, 2001.


  1. mikemulcahy

    mikemulcahy

    Jun 13, 2000
    The Abyss
    I was jammin with the boys when suddenlymy whole rig went DEAD!!! I shut everything down, and checked what i could. Found one of my amps was dead in the water, and one of the 18's it was driving was farting. I took the amp out of line, pulled the afflicted speaker and could see no obvious problems ( the voice coil and cone were intact). Replaced the speaker and tested is with another amp and now it works fine.

    The question is, could the speaker have an intermitant SNAFU and take the amp out and function normally after, and could this happen again. And should i replace the speaker?

    thanks

    Mike
     
  2. john turner

    john turner You don't want to do that. Trust me. Staff Member Administrator

    Mar 14, 2000
    atlanta ga
    hey mike

    i doubt the 18 was the problem at all.

    what's the amp you were driving the 18 with? and what are the specs on the 18 (impedance and watts)?

    sounds to me that your amp might have gone into thermal shut off, possibly due to impedance mismatch between what the amp was expecting to see and the impedance of the driver. that would cause the shut off, and impedance mismatch could also cause the farting.

    or your amp might've just had too many burritos. it happens.

     
  3. mikemulcahy

    mikemulcahy

    Jun 13, 2000
    The Abyss
    The Amp is a Crown Power base3, the speakers were 2 118 cabs @ 8 ohms each, 800 watts each.

    But the burritos could have been th culprit too.

    Mike
     
  4. That's a serious rig man! Sounds like a job for a tech to me. The farting noise sounds like capacitor release. I was thinking more like a good curry, followed by a prune dessert.
     
  5. john turner

    john turner You don't want to do that. Trust me. Staff Member Administrator

    Mar 14, 2000
    atlanta ga
    check your speaker cables. make sure you don't have any intermittent shorts. (as opposed to bermuda shorts). a shorting cable could cause that kind of behaviour.

    also, with the speaker disconnected, gently push on the cone of the offending 18" and listen carefully to see if you hear the coil rubbing anything - if that's the case, the speaker's blown. otherwise, i doubt the speaker is the problem.

    otherwise, take the amp to a tech - could be something with the output stage
     
  6. john turner

    john turner You don't want to do that. Trust me. Staff Member Administrator

    Mar 14, 2000
    atlanta ga
    check your speaker cables. make sure you don't have any intermittent shorts. (as opposed to bermuda shorts). a shorting cable could cause that kind of behaviour.

    also, with the speaker disconnected, gently push on the cone of the offending 18" and listen carefully to see if you hear the coil rubbing anything - if that's the case, the speaker's blown. otherwise, i doubt the speaker is the problem.

    otherwise, take the amp to a tech - could be something with the output stage. a tech should be able to do a complete coloscopy without getting his hands too dirty.
     
  7. mikemulcahy

    mikemulcahy

    Jun 13, 2000
    The Abyss
    Thanks Marty i have a very serious rig, I use 2 Eden 410's on top of 2 peavey 118 with 800w JBL's and a Crown Power Base 2 for the Edens and a Power base 3 for the Peaveys.

    John,

    I tried the speakers and it seems ok, no rubs like you mentioned, I have a spare Power Base3 to use. What are the chances of this happening again?
     
  8. You should check the DC resistance of the voice coil of the suspicious driver. If the rated impedance is 8 ohms, DC resistance should be 5.5-6.5 ohms. Use a digital ohmmeter, maybe a friend or a stage tech can lend it to you.

    Furthermore, use a 1.5 volts battery to test if maybe the coil was ripped off the cone. Try the battery both ways on the speaker terminals, and check if the cone moves both ways, especially backwards.

    I guess the following is a stupid remark, but be shure to use really fat cables for those cabs, at least 8 AWG or 2.5 mm^2

     
  9. mikemulcahy

    mikemulcahy

    Jun 13, 2000
    The Abyss
    Thanks Joris i will try that. And I do use 8 guage wires. Right now i am off to save the world from disease and disaster. I am ROBO DOC!!!! Master of the "treat 'em and street 'em" martial arts.
     
  10. john turner

    john turner You don't want to do that. Trust me. Staff Member Administrator

    Mar 14, 2000
    atlanta ga
    YOU WILL CEASE YOUR INTERNAL BLEEDING OR BE NEUTRALIZED. YOU HAVE 5 SECONDS TO COMPLY.