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? on blowing a multi speaker cab

Discussion in 'Amps and Cabs [BG]' started by Tualatin, Jan 3, 2006.


  1. Tualatin

    Tualatin

    Feb 7, 2005
    Atlanta
    Let's say you had a ported 6x10, and you noticed a huge tear around the cone on the bottom left speaker( like almost a full circle) and the speaker on the bottom right was scratching when you gently pushed on it.
    Why would the bottom two speakers get damaged first? And what did I do to deserve this?
    I play loud I guess. You could even say I "dig in," but am I wrong for assuming this top shelf gear should hang? Seriously.

    I've had nothing but problems with all of my stuff since I bought it, (blown tweeter, full retube on a new head 2 months later, blown 18 twice, massive fuzz and tone problems)
    I don't want to mention any brand names, at least untill after I talk to them, just doesn't seem right to sound whiny when it maybe my fault.

    I guess more so a question and a rant.
     
  2. Eric Cioe

    Eric Cioe

    Jun 4, 2001
    Missoula, MT
    Did you use unsaid company's "tested and approved" tubes? I hear their amps grow legs and walk away if you don't replace the tubes every three years with those special tubes. ;)

    Seriously though, wow. You must be playing really loudly, but with that company's gear, you'd think it'd be able to stand up to it.
     
  3. Tualatin

    Tualatin

    Feb 7, 2005
    Atlanta
    Yes sir, replaced under their 5 month tube warranty.
    I think the 18's are an issue of underpowering though.
     
  4. You don't have to tell us what the brand's name is, it's in your profile.
     
  5. eots

    eots

    Dec 18, 2004
    Morris, IL.
    Overdriving an amp can ruin speakers. The distortion(the bad kind) passes thru to the speakers in a bad way. A 300 watt amp can blow a 400 watt speaker.
     
  6. Eric Cioe

    Eric Cioe

    Jun 4, 2001
    Missoula, MT
    Yeah, but a tube amp would have to be pushed really, really far beyond the limit for this.
     
  7. eots

    eots

    Dec 18, 2004
    Morris, IL.
    Not if a tube was bad. Tube amps use much higher internal voltages than SS amps. Short something out and the potential for damge increases exponentially. I'm not saying that happened in this case though.
     
  8. The output transformer would prevent any DC short from reaching the speaker. A transformer won't pass DC.

    It's actually not that hard to get 400W from a 300W tube amp if you're overdriving it. Clipped waveforms have more power than non clipped ones of the same amplitude. You can get almost 2x clean rated power out of an amp if you overdrive it enough.

    Tears in cones aren't indicative of thermal damage, those are caused by mechanical overexcursion which can happen at power levels way below clipping. Boosting an EQ frequency that's below the cabinet tuning frequency can cause mechanical damage at quite low power..
     
  9. eots

    eots

    Dec 18, 2004
    Morris, IL.
    Maybe not the torn speaker but the other
    quote

    " I play loud I guess. You could even say I "dig in," but am I wrong for assuming this top shelf gear should hang? Seriously.
    I've had nothing but problems with all of my stuff since I bought it, (blown tweeter, full retube on a new head 2 months later, blown 18 twice, massive fuzz and tone problems)"
    sounds indicative of a distorted imput signal.
    Ideally, tubes need biased to give them each equal duty and maximum life. If the amp has been driven into clipping regularly possibly by 'digging in' and 'playing loud' even 'top shelf' amps will have problems.
    As far as the transformer . Doesn't matter. A rise and drop in DC can cause big problems if not checked . Put DC across a transformer then switch it off and the initial voltage rises absurdely before it drops. That's how one gets 30,000 volts across a spark plug in a car for a 12volt battery.
     
  10. Tualatin

    Tualatin

    Feb 7, 2005
    Atlanta
    It actually isn't Avatar, that is the name of the rehearsal space that we practice at. But yeah, I was worried that someone might put that together the wrong way.
     
  11. Tualatin

    Tualatin

    Feb 7, 2005
    Atlanta
    All the power tubes have been replaced, but I'm not sure about the pre-amp tubes. If one of those was bad, could that be the culprit and how would I know?
    Also, I've read about capacitor leaks, I know it shouldn't be a problem so soon, but is there a chance that could be an issue?
     
  12. It sounds to me like someone who does not understand what's wrong his amp attempting to diagnose the problems he's having with it more than any damage incurred by his playing style. An underbiased or defective-tube equipped amp can have exactly those same symptoms irrespective of input.

    Yes.

    That's ridiculous. A 'hard-clipped' tube amp puts out a signal with increasingly distorted harmonic content, but unless the power output is greater than the speaker's rating or the low frequency content is excessive below the speaker cab's tuning(probably what happened to the 18's), no damage will result. If you have an amp running its tubes above their limit and barely biased, then MAYBE you'll hurt the amp, but it will be from the tubes going into overcurrent-not the playing. The unnamed amp uses 12 conservatively run 6L6 type tubes well within their tolerance.

    I beg to strongly differ. If the transformer didn't matter, it wouldn't be there. It's very purpose is to isolate the speaker from the high voltage DC of the B+ supply that is ALWAYS present when the amp is operating. The AC current of the speaker output is induced by the DC changes, but unless the transformer is dead-shorted (which will cause mucho-fireworks), it will always be AC.

    The leads of a meter are as close to an infinite impedance as possible in order to take accurate voltage readings. Connect the secondary leads of that same transformer to a LOW impedance source that can safely disappate the induced current, and you've just made an output transformer.
     
  13. eots

    eots

    Dec 18, 2004
    Morris, IL.
    I am limited when it comes to my knowledge of tubes and their required circuitry. However, They use voltages of like, 300-400 volts DC. The tubes have to be 'biased' which ,While I have never done it myself, requires adjusting resistors by rotating a pot or changing values of fixed resistors so that matching pairs of tubes are generating the same level of amplitude.
    Ideally, this would by done at the factory but subsequent retubing should be checked ,even though they are generally bought as 'matched sets', by matching plate voltages and biasing current for each pair of tubes.
    I suspect that this probably is not the situation with your amp as it seems your amp is not the problem. However you might consider having it biased and recapped if it's more than 10 years old. Caps do go bad with time and leaky caps do occasionally pass thru quality control.

    Does the amp have an input clip light? or input gain pot?
    It could be a coincidence that bad speakers could be a problem and replacements will last a long time.
     
  14. Tualatin

    Tualatin

    Feb 7, 2005
    Atlanta
    Here is the whole timeline of events.

    The twelve 6l6 tube power section head was bought "new" at guitar center in march of 05. It seemed to be a floor item and was at a discounted price, but still classified as a new head. At the same time I bought a new ampeg 2x15 cab which came a week later. When I finally played both, the rig sounded terrible. Lots of farting at low volume. The guy at GC told me to bring in the head and we'll try it out on some different cabs with my bass and some other ones. We hooked it up to an ampeg 8x10, and the problem seemed to have gone away in the store. I traded the 2x15 for a unmentioned 6x10, and later that week bought a used unmentioned 1x18. The farting hadn't completely gone away, but just came through at higher volumes. Well at this point I'm broke, don't know what to do, but this tone will work for now. A month later, the 18 and the tweeter on the 6x10 started to crackle. I figured the 18 was old with no warranty left, so I bought a Peavey Black widow to drop in the cab. 2 weeks later, that blew. The tweeter was fixed under warranty, but the same week it was in the shop the entire back row of power tubes would intermitenly flash and loud crackles would come through the 18 (before it blew).
    This is June now, and my 6x10 and head are in the shop and the 18 is blown. I get the head and cab back with a full retube and a new tweeter, and it sounds a hell of alot better, but still has no head room. I tried every possible configuration of safe ideas(e.g. active bass, passive bass, mxr pre-amp to control input level, pickup height, eq settings, etc) but still no head room. Now it was like an over driven tube amp should sound, but at way low volumes.
    Now, 2 months ago, I noticed that the bottom left speaker sounds like ass, and I determined I've blown that one now along with the tweeter again. Im poor so I fiqured I'd just wait and save up and start to fiqure this stuff out again after x-mas.
    Over the weekend, I bought some 1/4 pounders and a conklin .150 snakskin string. Yesterday I was messing with the set up and tone (this we'll definetly be my fault) and like I said at the begining of the thread the bottom left speaker now has a massive cirrcular tear in the cone and the bottom right is scraping when i gently push on it.

    I just talked with the unmentioned company, and they were really cool. It's going to go back to the shop this week and we're going to go from there. But any speaker warranty is up in the air until they determine their diagnosis.

    Please don't hold back any observations of stupidity on my part, I need to learn from these mistakes. I need to know ecaqctly what I'm doing wrong and what I should expect from my gear.
     
  15. Two questions:

    1. What are your EQ settings?

    2. How do you hook your 6x10 and 18" cabinet to the amp?
     
  16. I meant in your profile where it says what gear you own........lol. I won't mention the brand name though.
     
  17. eots

    eots

    Dec 18, 2004
    Morris, IL.
    Maybe the tear in the one speaker came from the guy in the shop fixing it. I doubt the GC crew are highly qualified techs making top dollar.
    "OOP's dropped a screw driver. OH $%#@!. :eek: Maybe he won't notice."

    Sounds like your amp has issues for sure. Get a replacement.
    It's a tough go when you're at the mercy of a dealer.
     
  18. Tualatin

    Tualatin

    Feb 7, 2005
    Atlanta
    For most of the past year I ran the parametric flat, and the graphic with a frown mid boost. That's when the 18 blew. Recently I cut out some of the upper mids, and most of the treble, and boosted the lows a bit more, that's when the 10 blew.
    There were a few times when I was messin with it and had only the lows boosted all the way up, but the input gain never got to high and it wasn't for that long either.

    The 6x10=4ohms, 18=8ohms. I initially ran the 6x10 out of the 2ohm, and the 18 out of the 4ohm, when they were together. Solo, they were ran out their respective outputs. I tried different combinations of that to(daisy chain@2,4,8ohms etc.) but that didn't change anything either.;
     
  19. Tualatin

    Tualatin

    Feb 7, 2005
    Atlanta
    oops
     
  20. Nothing too strange there; certainly nothing that should be eating speakers with the 300 watts that the Mesa 400+ (oops!) :eek: ;) puts out.

    The gain setting might not matter, but the thing about overexcursion is that you can usually hear it quite clearly. The speaker crackles and and sounds like rubbing paper. You'd have known if that was doing damage.

    I suspected this. Contrary to what most people think, those outputs are NOT a mix'n'match proposition. You only get to use ONE at a time. For your combination you should have used ONLY the 4 or 2 ohm output with the two cabs paralleled into each other (I'd use the 4 for safety), not separate output taps. Your output was probably anemic due to your trying to use two taps off the output transformer at the same time, and you were giving your output tubes a fit, too, hence the needed retube. Mesa should make that more clear that you can only use one output tap at a time, because it's a common misconception.

    Since it was a floor model, chances are that you weren't the first to do this, and once damage is done, the amp will not "heal" itself. I'll venture you've NEVER heard your amp healthy.