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Big twin 2 distorting.

Discussion in 'Amps and Cabs [BG]' started by Phillip Forney, Nov 26, 2017.


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  1. My big twin 2 has developed a crackle in the tweeter at medium volumes. Protection circuit bad? I tried to upload a video of the problem. Too large of file. Can the sensitivity of the protection circuit change over time? It seems to happen at lower and lower volumes. Thanks for any help. Btw, I’ve sent an email to Barefaced’s, but I’m impatient.
     
  2. As he designed the cabinet Alex is the guy to ask. :)

    Edit: Like as not there is a protection lamp on the crossover board. You could take the lamp out and clean it’s contacts and reseat it. Could also be that the filament is making intermittent contact and the lamp should be replaced.
     
    Last edited: Nov 27, 2017
  3. That sounds like the problem. I’m going to try to get the input panel off and see. Thank you.
     
  4. just email Alex - they will get back to you!
     
    rodl2005 likes this.
  5. Disconnect the tweeter. Problem solved. :p
     
  6. DukeLeJeune

    DukeLeJeune rational romantic mystic cynical idealist Supporting Member Commercial User

    Nov 24, 2008
    Princeton, Texas
    Owner & designer, AudioKinesis; Auth. mfg, Big E (Home Audio only)
    Just my opinion, but I think it would have been considerate towards Alex to give him a chance to respond to your email before starting this kind of thread.

    Well, in this case it may not be so simple.

    Chances are the highpass filter on that kind of tweeter is at least second order, and if that's the case, without the tweeter's resistance in the circuit, there may be a frequency at which the impedance will dip quite low, perhaps down to a small fraction of an ohm. This is highly counter-intuitive (it arises because of a now-underdamped resonance between the series capacitance and the shunt inductance), so you'd have to be a fairly hard-core crossover geek to be aware of it. Sometimes a second-order or higher crossover has some resistance deliberately included in a shunt leg, which would tend to damp the resonance and protect against a really deep impedance dip if the tweeter fails or is otherwise removed from the circuit.

    Don't worry if none of the preceding paragraph made any sense. It's not on the final exam.
     
  7. As an aside, can a woofers impedance change from damage?
     
  8. Alex and I got the problem sorted. Seems that one woofer had a partial shorted voice coil. When full tilt boogie was attempted, the thing would short. I assume the tweeter protection circuit was also responding to this. I got to say, I’m impressed with the customer service in this case. Awesome!
     
  9. DukeLeJeune

    DukeLeJeune rational romantic mystic cynical idealist Supporting Member Commercial User

    Nov 24, 2008
    Princeton, Texas
    Owner & designer, AudioKinesis; Auth. mfg, Big E (Home Audio only)
    The woofer's impedance could go to approximately zero (shorted) or infinite (open). Depending on the voice coil's construction and where the short occurred, impedances between zero and the normal impedance are possible.
     
    Last edited: Nov 27, 2017
    mobdirt, BadExample and Arjank like this.
  10. Thanks Duke.
     
  11. Maybe off topic but what do you think of that particular cab? That’s the 2x15 right? Thinking about selling my ampeg cabs and getting that one or maybe even the 212. Want something as loud as an 810 that’s a little lighter (we rehearse on the second floor and I have to carry everything up a flight of stairs. Also a more full range sound for the smaller gigs I play where there’s no bass in the PA would be nice. I run an Avalon u5 into a crown xls 1500.
     
  12. It’s the big twin 2, which is a 212. It’s pretty nice. Very light. I have not played it loud yet. Considering only one driver had been working, it’s pretty awesome.
     
  13. I got my big twin 2 working again. This thing is a monster! Alex sent me a new 12” driver. I’m very impressed. First class customer service. Thanks Alex.
     
    wave rider and svtb15 like this.

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