Blown speaker...or what? Help!

Discussion in 'Amps [BG]' started by LeeInAustin, Apr 22, 2012.


  1. LeeInAustin

    LeeInAustin

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    Newbie here! I'd love yer help. Rig is in signature. Avatar 8 ohm 2x10 cab w/ Neo speakers + tweeter (w/ attenuator dial on back) has been crackling at higher volumes.

    So I tried using just one speaker at a time to see whether one was blown. I took out one of the 10's, and it played fine. Took out the other, and it would play, but only very briefly and at extremely low volume, then make a quiet popping noise and go silent. If I waited a bit, turned amp off and on, unplugged speaker cord and replugged it (guessing all this amount to Wait A Minute), it would play again...but still only 'til I gave a little volume, then shut off again.

    I don't see visible evidence of a blown speaker, but I might not know a blown speaker if it were staring me in the face! Does it sound like I need to replace the speaker that shuts down when it's given any real volume? Or do you have a different diagnosis?

    Thanks a million. I've enjoyed lurking as a non-member; glad to be on board now. Lee
     
  2. billfitzmaurice

    billfitzmaurice

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    Drivers don't shut down, amps do, usually from overheating. Overheating can be caused by a short circuit in the voice coil. It needs to be tested by someone qualified.
     
  3. Andyman001

    Andyman001 Supporting Member Supporting Member

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    If you have access to a multimeter, check ohm reading across the terminals. An 8 - ohm speaker should read about 6 - ohms.

    GENTLY move the speaker cone in and out and listen/feel for scraping of the voice coil windings inside. Feel / hear anything = bad.

    Use a 9-volt battery on the terminals, should move forward or back while battery is attached.

    Andy
     
  4. Andyman001

    Andyman001 Supporting Member Supporting Member

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    and listen to the smart guys like Bill
     
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  6. LeeInAustin

    LeeInAustin

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    Whoops. Rest of rig didn't show up in original post:

    Epiphone Allen Woody (short scale, mini-hum pups) / George L cable / MarkBass Little Mark II head / Avatar 2x10 cab w/ Neo's
     
  7. billfitzmaurice

    billfitzmaurice

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    I've encountered situations where a DCR reading didn't reveal a bad coil. An impedance sweep will. Of course if you get a DCR of zero then it's blown for sure.
     
  8. LeeInAustin

    LeeInAustin

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    I'll try Andy's suggestions now. I do have a multi-meter, though I'm not experienced with it. I really appreciate the help. Bill, what's a DCR? Thanks, Lee
     
  9. johnk_10

    johnk_10 vintage bass nut

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    DCR= DC resistance. a DC reistance reading of 0 ohms means that it's shorted. if it doesn't get a reading, it means that it's open. in both cases, the speaker need to get reconed.
     
  10. LeeInAustin

    LeeInAustin

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    Thanks, Bill. First useful multi-meter reading of my life = 12ohms DCR between terminals with speaking completely detached from amp. Given what Andy said about 8 ohms reads as 6 and that this is one of 2 speakers in an 8 ohm cab, I'm guessing that 12 reflects that the speaker is at 16 ohms, where it's supposed to be (?).

    Moving cone in and out didn't seem to create any strange (or even noticeable) noises.

    Touching terminals of 9V battery to speaker's terminals pushes cone out (and back in), then if I reverse the battery's terminals, IN, then out.

    So is all that normal? And if so, what does this tell us? Thanks
     
  11. LeeInAustin

    LeeInAustin

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    Hmm, wonder whether the shutting down (of the amp, apparently) had to do with heating up from running these little tests. The MarkBass manual doesn't say what resistance is / isn't ok, but it only lists power ratings for 8 ohms (300) and 4 ohms (500)...wonder whether doing the tests w/ only one speaker at a time showed the amp 16 ohms and therefore created a problem.
     
  12. RickenBoogie

    RickenBoogie

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    No, a 16 ohm load would not hurt the amp. Only going UNDER the rated impedance will hurt.
     
  13. Andyman001

    Andyman001 Supporting Member Supporting Member

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    Do tests on good speaker too. and compare.

    also amp would 'cut out' with both/either speaker
     
  14. B-string

    B-string Gold Supporting Member

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    If both speakers work when connected but one makes noise, hook up one at a time and one stops, it is NOT amp shutdown. The speaker that stops working could have a nicked wire in the voice coil winding or poor connection in the flex leads.

    Connection from the flex leads to the terminal board are the most likely.
     
  15. LeeInAustin

    LeeInAustin

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    Thanks, guys. Same results from all tests on good speaker (12 ohms, no noise from pushing cone in/out, 9v battery makes cone go in/out).
     
  16. Bass_Pounder

    Bass_Pounder

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    Are you testing the speakers independant of the cab ?

    Or, are you just "disconnecting" the leads from one speaker and testing the cab with only speaker connected ?

    Reason I ask is that it *could* be in the cabs wiring itself (bad solder joint from the crossover, bad connection at the speaker, etc.).
     
  17. LeeInAustin

    LeeInAustin

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    Yes, testing speakers independent of cab: removing 'em from cab, detaching leads.

    I've wondered about cab's wiring. Solder joints LOOK okay to a non-expert eye. The only thing I can see that raises an eyebrow is that the middle (of three) lug on the tweeter's attenuator has a lot of side-to-side give in it. It and one other lug on the attenuator pot has a wire attached to it.

    Thanks.
     
  18. B-string

    B-string Gold Supporting Member

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    You need to look closely at the flexible leads coming from the speaker's cone to the terminal board on the basket.
     
  19. Big Band Hand

    Big Band Hand Supporting Member

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    It also may be a cold solder joint on the speaker terminal. Your problem has the same symptoms as a cold solder joint. Although the connection looks good even to a trained eye, it may not be. Try just holding a solderiing iron on the terminal on the speaker where the wire connects to the speaker - A BIG CAUTION - put something underneath the speaker terminals so solder does NOT drop on the cone or it may get damaged. You may want to hold the phone (don't do anything else) and just call Avatar to ask for advice... I hear they are pretty good about. There are other options but from all of the good advice you got here, most everything else is covered.
     
  20. will33

    will33

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    Agreed on checking the tinsel leads, solder joints, etc. It could be that coil got a "hotspot" that doesn't manifest itself until it warms up from playing it. Checking DCR cold doesn't always reveal the problem. You say a terminal is loose on the l-pad. Possible problem there too. If you get the woofer thing sorted out, try running them direct, bypassing the filter/pad/tweeter.
     
  21. will33

    will33

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    Avatars also have an LPF in the crossover. Possible bad solder, cap, or inductor got hot there too. Both woofers test the same. Rig them up to a jack and try playing them without the crossover, that could help narrow it down.
     

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