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Okay, I think I did something bad

Discussion in 'Amps and Cabs [BG]' started by bryan bailey, Oct 21, 2004.


  1. I was crankin' my new PLX 2402 with the rest of my amp, and the BSE I have.

    Okay, I was jammin out, volume on power amp alomst on full, and I notice a faint smell of smoke, and I figure it's nothing. After about 30 more seconds I saw smoke coming out of where the tweeter used to be(I removed it, but kept the plast plug thing in).

    So after that, I stop playing, unplug it quickly, and see smoke slowly billowing out the bottom ports, a very thick accrid white smoke, and I blow into the port, and I'm hit with a cloud of white smoke, and I knew at this point, something bad has occured.

    I have since put a fan up to it, opened up the back pannel, and let it air out.

    The question is, what exactly went bad, and what damage I did to it?

    Anyone has experience with blowing up cabs in the mannor that accured?

    Edit, the cabs a BSE 4x10 HLF (ampeg) 400 rms, 800 program, 4x10's, no tweeter, one side of the PLX so 700 @ 4 ohms.
     
  2. What did you do with the tweeter wires. Did you remove them from the crossover assembly or did they dangle.

    Theory 1: If they were loose inside the cab, my guess is that they moved around with the air pressure and managed to touch each other, creating a short, compounded by you cranking it.

    Theory 2: The bottom cab and the tweeterless tob cab created a 2ohm load and you fried your amp.

    Theory 3: Spontaneous Combustion

    Theory 4: Vibration-induced ground short in the power amp.

    Theory 5: You simply over drove your amp, did not notice the clipping without the tweeter and cooked your PC board.

    Likeliehood you voided your warranty: 74.5%
     
  3. {OE}

    {OE}

    Sep 23, 2004
    Connecticut, U.S.
    I would assume its the cab as the smoke was comming from the cab, not the amp. If possible try your "amp" through another cab.

    My first thought was that you fried your crossover ( which I did in my Eden 4x10, smoke and all.... :eek: )
     
  4. Well, there is only one cab involved.

    And the tweeter is totaly removed, wires and all, and the power amp wasn't clipping at all.


    But now that I think a bit further into this, I see it as

    A. A speaker combonent was getting very hot, and partially melting, or whatever.

    B. The sound proofing foam stuff in the cab drooped on the very hot speaker magnet causing some melting, and smalle smolderingness.

    I left the cab outside and aired out the house for a while now, so I'll play it later tonight and see if it still works.
     
  5. The speaker got hot enough to melt insulation stuff? I've fried some speakers in my day, but not like that...
     
  6. bigbeefdog

    bigbeefdog Who let the dogs in?

    Jul 7, 2003
    Mandeville, LA
    Hot speaker magnet? Sounds unusual...

    I suppose it is theoretically possible that there was some sort of short inside one of the 10's, but it sounds unlikely.

    Before you try to play it again, take a close look at the wiring. ALL the wiring. This sounds more like burning wire insulation, which is usually a symptom of a short circuit (overcurrent).
     
  7. Hmm, the wire melting sounds about right.
     
  8. depending upon the fill material, it will smoke when melted. it's completely fireproof, but when in contact with extremely hot crossover components can melt and smoke in a very unpleasant-smelling manner. or it could be the crossover components themselves. there is an off chance one of the voice coils melted and began to smoke, but i would have trouble believing that much smoke would be created without an accompanying fire. the sight and sound of such would be very obvious.

    robb.
     
  9. 700 Watts into a cab rated to handle 400 Watts would explain your problem pretty easy.

    It may say 800 Watts program, but thats short duration spikes in power..not constant.

    Too Much Power = Speaker Melt Down

    YMMV of course
     
  10. alexclaber

    alexclaber Commercial User

    Jun 19, 2001
    Brighton, UK
    Director - Barefaced Ltd
    I doubt that's it unless the amp was riding the limiters. Was it?

    Alex
     
  11. Well, all he would need is a constant above 400 Watts to do it.
    The Gains would not have to be cranked all the way for that.

    In theory it should be able to handle it, but sometimes they cannot.

    Could have been a component in the crossover not rated to handle that much power also.
     
  12. bigbeefdog

    bigbeefdog Who let the dogs in?

    Jul 7, 2003
    Mandeville, LA
    Not likely; bass playing wouldn't feed a "constant" to the cab (unless, maybe, you plucked the A string and just let it ring out, for example). The 800W program refers to just that - 800W power handling when fed program material (like a bass line).

    Really sounds like a short, and something burned up - either wire insulation or crossover, or possibly cab filler material.

    The good news is, if that is the case, you can fix it yourself. Heck, if you pulled the tweeter, you wouldn't even *need* to replace the crossover - just rewire the cab without it.
     
  13. Not likely the cause of your meltdown, but the question that would spring to mind is "I wonder what removing the tweeter does to the impedance of the cabinet"?
     
  14. bigbeefdog

    bigbeefdog Who let the dogs in?

    Jul 7, 2003
    Mandeville, LA
    Good question - I wondered that myself.

    I think the answer is "not much", especially if there's a tweeter attenuator on the cab (which places a resistance in parallel with the tweeter, so you can adjust the voltage divider/resistance on that "leg")... but it would be good to hear from those in the know.
     
  15. Jerrold Tiers

    Jerrold Tiers

    Nov 14, 2003
    St Louis
    Did you remove/disconnect/turn off the crossover?

    Or was it still in place and you just pulled out the tweeter?

    If you remove the tweeter you need to disconnect or disable the crossover. That isn't really easy for units where the crossover is on the jackplate.....UNLESS YOU SIMPLY SET THE TWEETER SWITCH TO "OFF". THEN YOU DON"T NEED TO REMOVE THE TWEETER OR PERFORM ANY MODIFICATIONS.

    The problem is that at the crossover frequency, if there is no tweeter in place, the tuned crossover components have a "series resonance" and they present a very low impedance in that frequency range. If you get on a close note (or a close harmonic, more likely) enough, you may "cook" them due to heavy current flow.

    I just recently posted elsewhere that we don't authorize modifications. And we don't. I need to be careful here.

    So, for the legal disclaimers: this response is not "Authorization" to perform this or any other modification, it is an explanation of why that particular "unauthorized" modification (removing a tweeter) might cause a problem.

    If the tweeter is replaced (or never removed at all), and is turned "OFF", you will get the same result as if you removed it. But the chances of a resonance-induced overstress/overheating situation with an internal part are reduced.

    The recommendation is to have the unit restored to original condition, and turn the tweeter "off".
     

  16. Yeah dude that's right. More power is LESS harmful.

    LESS power is more likely to blow speakers and fry voice coils.

    All Amps clip.
    Many players overdrive their amps into clipping.
    Cliiping results in exponentially increased, distorted squarewaves.
    Said distortion fries voice coils.

    Ergo, some players with underpowered amps blow speakers.

    Players with more power, like this dude, are less likely to blow a voice coil from cranking his amp over its limits.
     
  17. I had a friend of mine rewire the cab so the 10's get full rang, the cross over is bypassed. Funny, cause I had the tweeter removed and bypassed because I blew the protection light, and didn't feel like replacing it.

    I'm fairly sure I melted some sound proofing material in the cab, because it was horrendously bad smelling white smoke, and when I looked in the back of the cab, I could see no visible cone damage.

    But I'm gonna plug her back in, and see if it'll still make noise.

    Update in a few.
     
  18. What you said about clipping an amp is true, but thats a different subject than this.

    It is very possible to fry a voice coil from too much power, I have seen it done probably over 50 times.

    Not gonna get in a posting fight over this but I have been repairing pro audio equipment for over 10 years
    I don't claim to be an expert, but I do know what i'm talking about
     
  19. Okay, I just plug it in, and all the speakers are moving, making sound, and aren't distorting.

    So I think we are looking at a non speaker component melting in the cab. I've yet to actually check the voice coils or the wiring, but something or other did melt.
     
  20.