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Burnt smell from cab (LMII/Warwick 4x10)

Discussion in 'Amps and Cabs [BG]' started by Misanthropic, Oct 7, 2013.


  1. Hello,

    I've been reading up on threads concerning burning smells out of cabs after experiencing this myself last weekend.

    My band played with a very noisy crust punk act, who used my gear. Markbass Little Mark II and Warwick WCA 411 PRO (4x10, 4 ohm, 600 W). The bass player was doing the following:

    - bass straight into amp
    - gain a bit too high so the clip light would go on about constantly
    - tuner out -> distortion pedal -> guitar amp

    Burnt smell coming during their gig, no one found out from where until after their set. However, I tested the setup with my own bass and pedal (Music Man and SansAmp BDDI) and it sounded normal to my ears, also performing at normal volume. The environment at that point (alcohol and noise) wasn't suitable for more precise testing.

    When I get the time, I will, according to the other threads,

    a) test the speakers with a 9V battery
    b) see if the tweeter is working (I've always had it turned only a couple of millimeters up, for maybe two years now).

    What I wanna know is what caused this? The clipped signal? The tuner out thing? I thought the Markbass gain stage would handle clipping safely, not producing dangerous peaks? The master volume wasn't set high at all, didn't see the eq settings but to my ears most of the noise was coming out of the mentioned guitar amp. The speaker cable was a DIY one, with speakons, thick gauge and same one that I've used for longer than I've owned the cab.
     
  2. Bassmec

    Bassmec

    May 9, 2008
    Ipswich UK
    Proprietor Springvale Studios
    So what was the position of the bass control on the bass guitar he was using?. he was probably dime'd and using, his active pre amp EQ to overdrive your rig by as much as 14 dB at circa 50Hz thus forcing your cab to make heat instead of sound.
    It can take many years of intensive training to teach crust punks anything at all about amplification or for that matter detergent, soap, oh and incedentally music.:D
     
  3. Don't know about the bass settings. Didn't think it would be possible to do a thing like this with an amp like the LMII.

    I agree, except I can enjoy the music and overall chaos.

    A question that I didn't find an answer to in the other threads would be, can a cab smell burnt and still be intact? Or will something most definitely be broken (speaker, tweeter, crossover...)?
     
  4. Anyone? Do you all agree on that this was caused by just boosting a particular frequency (i.e. bass) too much?
     
  5. anderbass

    anderbass

    Dec 20, 2005
    Phoenix. Az.
    If all of your 10" speakers are still working/sounding good, I'd suggest you unscrew the input jack plate, pop it out and look/smell inside for any burnt crossover components.

    If you find all your speakers still work/sound fine, but one of your crossover components are indeed burnt, then the problem was most likely caused by having the horn attenuator knob turned way down for a long time.

    And then if you discover a crossover component is burnt, (and you prefer the horn turned off anyway) you could save money by simply bypassing/wiring-around the entire horn circuit :cool:




    [​IMG].
     
  6. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    The crossover splits the signal into lows that go to the Woofer(s). The highs are sent to the Tweeter via the L-pad. With the L-pad almost off the highs have to dissipate across the L-pad. So 300W worth of highs across what is likely a 50W. at best, L-pad. I'm not surprised you smelled smoke.
     
  7. Thanks for your replies. Before reading these threads I didn't know that NOT using the tweeter would damage it.

    Which makes me wanna broaden the focus of this thread:

    What I don't get is, why are bass cabs designed that way? Why isn't there a fuse or something that would pop if a component can't take the stress? Why is it even possible to turn the tweeter all the way down if it only does damage? Why not include a button that instead removes it from the circuit?
     
  8. Implosion

    Implosion

    Oct 19, 2007
    Finland
    Moro,

    Mulla kävi aikanaan samalla tavalla samalla kaapilla ja pillin/tweetterin "auki" pitäminen poistaa ongelman. Karkeasti ottaen kyse on siitä kun vahvistimesta tuleva sähkö ei pääse muuttumaan ääneksi, niin se muuttuu jakosuotimessa lämmöksi.

    Ampeg on muun muassa ratkaissut tämän ongelman jakosuotimessa olevalla hehkulamppusulakkeella, jossa ylimääräinen sähköenergia ohjataan sulakkeena toimivaan hehkulamppuun, eikä se siis kuumenna vastuksia kuten Warre. Tämän vuoksi jossain A:n kaapeissa voi nähdä sisäisen valoshowvälkkeen. Warren kaappeihin ainakin sai ennen valmiita crossover vaihtopaketteja, jos sattui kokonaan kärähtämään.
     
  9. Kiitos infosta. Pitää ruuvata takalevy irti ja tsekata. Jos vaikka ohittais kokonaan sen pillin, kun tällä hetkellä ei kuitenkaan ole tarvetta, ja sitten jos kaappi lähtee esim. myyntiin niin hommaa sen vaihtopaketin.

    ---

    Sorry for not discussing in English. The above concerns Ampeg fuse systems and Warwick crossover replacement kits.
     
  10. Goteky45

    Goteky45

    Oct 30, 2009
    Portugal
    warwick once said in their forums that they use an high pass filter for the tweeter instead of a crossover.
    also, since the bass player used the tuner out to drive a guitar amp without cutting the lows going to said amp, couldnt it be the guitar amp burning instead of yours?
     
  11. The bass cab smelled, the guitar amp didn't.

    I found the forum thread you mentioned through a google cache:

    I don't know how high pass filters work on a physical level, but would it be possible to fry them in a similar way as a crossover? In that thread, the Warwick staff didn't warn OP about having his horn turned down all the way.
     
  12. Stumbo

    Stumbo Wherever you go, there you are. Supporting Member Commercial User

    Feb 11, 2008
    Intergalactic Mind Space
    Song Surgeon sofware
  13. alexclaber

    alexclaber Commercial User

    Jun 19, 2001
    Brighton, UK
    Director - Barefaced Ltd
    Most bass cab crossovers are just a highpass filter on the tweeter - it's still a crossover though, but only the tweeter half has electrical components whilst the woofer half is just effected by the acoustic function of the woofers.
     
  14. Allright, so the l-pad definitely got hot. This is what it looks like, and does not work. The foam padding sitting on the l-pad melted (2nd pic), so no wonder it smelled quite a lot.

    [​IMG]

    [​IMG]

    So, I was thinking about just bypassing it for now. How would I go on about doing that? Just disconnect the cables leading from the normal jacks to the high pass filter circuit (which I assume is both the l-pad and the orange thing next to it)?
     
  15. AlexanderB

    AlexanderB

    Feb 25, 2007
    Sweden
    Lpads are generic in function as long as the impedance is the same. See if you can fit a physically bigger Lpad (with higher power rating). Cut away some of the lining also so it can radiate some of the heat away. Stupid Warwick people to INSULATE such a heat sensitive component...
     
  16. Matthijs

    Matthijs

    Jul 3, 2006
    Amsterdam
    If you had the L/pad down all the time anyway, it would make the most sense imho to just disconnect the tweeter. Other alternatives for buying a higher rated l/pad are putting in a on-of switch for the tweeter or constantly padding the tweeter with a network of high power resistors, one parallel to the tweeter and one in series.
     
  17. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    Which is what the L-pad essentially does. I would agree that if you never use the tweeter then a simple on/off switch is a simple mod to make. From the photo your L-pad is indeed a 50W at best unit. The 100W would be better electrically but I doubt you have the room to install one. Possibly by moving some stuff around you might be able to get it in there.
     
  18. BassmanPaul

    BassmanPaul Gold Supporting Member

    Aug 25, 2007
    Toronto Ontario Canada
    It is kinda rude to exclude from the conversation folk who are trying to help you! This is, after all, an English language forum though we do allow some American. :bag:

    :D
     
  19. I don't think I'm gonna mod it now, since that would involve buying and installing at least a new l-pad. The cab was bought for quite cheap, for my punk band doing lots of DIY gigs where everyone's using the same backline. Point was not having to worry every time someone is borrowing my rig. All in all, I don't even like it that much (bulky, dry sounding), and have my lightweight EBS's for all my high end needs :).

    So, I will disconnect the tweeter. The question I'm still asking, though, is how to do this. I'm thinking just disconnecting the cables leading to the components right of the burnt l-pad would be it, but I wanted to be sure.
     
  20. The two glued orange caps are the crossover caps, clip the wire from the input jacks to those caps and you're done.
     

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