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thumping speakers

Discussion in 'Amps and Cabs [BG]' started by basswhiz1, Nov 3, 2002.

  1. basswhiz1

    basswhiz1 Guest

    Nov 3, 2002
    I have a peavey nitrobass connected to a peavey 4x10 4 ohm cabinet. Occassionally the lower speakers will "thump" or "pop" 6-10 times or so then stop.
    I've tried turning the volume and gain all the way down when this happens to see if this was the culprit,but no difference.I've also turned down the HF control on the cabinet,but again,no difference. My gear is about 6 months old and hasn't been abused. I've also tried all three ground settings. I'm wondering if this might be a power issue?
  2. Are only the bottom 2 speakers in the cab doing this? Not all 4 of them?
  3. It sounds like your amp is sending them DC. You will only see it in part of the speakers because they're connected in series/parallel. Get your amp looked at.
  4. What Psycho said.

    Bad cap maybe?
  5. Agreed. Must be it.
    Why's this? Some speakers doing it, and some not because of series/parallel connection? Come on, you know better than that ;) If the speakers are connected in series/parallel they will still all do exactly the same thing. Unless they are crossed over, and the top speakers have a high-pass on them. That would protect them from DC. If they're not crossed over, they must be blown, because they're not moving.
  6. I'm not disputing your word, Lord knows I have a lot to learn about the inside of an amp, but, why would only the bottom speakers move if it were wired in series/parallel?:confused:
  7. originally posted by Joris
    No they won't. If there was no difference, then both connections would provide identical current transfer. Provided of course that the others aren't blown, a DC impluse will see a higher equivalent resistance between speakers connected in series than the others in parallel. This is not a sustained current source but rather a DC transient. It takes the path of least resistance and by the time it has moved the speakers connected in parallel, it is disappated, hence the speakers connected in series don't move, but the ones in parallel did.

  8. Yeah right, whatever.

    No matter how you twist it, the same current will run through all four voice coils. Period. Don't talk to me about the speed of current, because last time I checked, it runs at roughtly 200,000,000 meters per second.
  9. So the current pulse runs out before it ever makes it to the other 2 speakers?
  10. Haha, this reminds me of the following school pop quiz:

    Q: "Why is there only one wire connected to a bicycle headlight?"

    A: "The current the generator supplies, is equal to amount of current consumed by the bulb, so a return wire is unnecessary"

  11. Jeff Moote

    Jeff Moote Supporting Member

    Oct 11, 2001
    Beamsville, ON, Canada
    Joris, your screen res is crazy! I'm using an LG 19" flatscreen and I can't stand any larger than 1280x960 though that's where I like to stay.
  12. No, the ESR of the series wired speakers simply channels more power to the other speakers. All four speakers see different amounts of power from the same current due to their connection types. Joris may think he's cute, but he needs to check with Ohm's Law. If there is no difference between series or parallel connection then why is there an impedance difference between them?
  13. My girlfriend thinks I'm quite cute, yeah.

    ESR is applicable to capacitors. See http://emcesd.com/tt020100.htm

    I checked Ohm's law. And Mr. Ohm is right, the speakers get the exact same power, because they have the exact same impedance.

    You're gonna have to severely back up your story. Even if you came up with all the phoney evidence that you're right, you would still not convince me, because of the simple fact that you're wrong. Man, you are hard headed (again, might I add)!
  14. Equilavent series resistance, as in the equivalent impedance resulting from capacitance, inductance, reactance, electromotive feedback, and a whole host of other influential factors is different for each wiring configuration because of the current flow properties imposed differently by each type of connection. Ohm's law supports that, no matter what your personal feelings towards me are. I have made my case and, yet again, the best you can say is that you're sure that I'm wrong because, well, you say so. Whatever..:rolleyes:
  15. So you truly believe that the designer of a 4x10 would allow for an uneven power distribution of the 4 speakers in his cab? Assuming this is possible by connecting the speaker in series/parallel

  16. i agree with joris here, as all the speakers are 4 ohm...2 pairs of series that are paralell with each other...4+4 = 8, 8 and 8 in paralell = 4. now if all speakers are the same resistance they will have the same voltage drop across them, and current is common to ALL components of a series circuit, and if both sides of a parallel circuit are of equal resistance then current is equal through both sides. as (i think it is) kirchoffs current law the sum of current flowing through a parallel circuit is equal to the current supply.
    if u think of current as a fluid running through pipes...u can't have a sudden burst of fluid in one section of pipe can you...the surge of fluid will run all the way through the pipe, like a shokwave.
    so all speakers will see/receive the DC spike.
  17. If the speakers are hooked up like in Joris's drawing, and they are all equal impedance, and none of them are blown, then they will all move equally.

    My guess is that there is something else involved here, like the guy is plugged into one of the "stereo" jacks that splits the speakers in seperate pairs instead of being plugged into the "mono" jack, or else one of the speakers is blown, or a wire is loose in one string, or something.

  18. Please don't confuse your pissing match with Joris with my question. I understand that you are talking about DC and not AC which is what a speaker is suppose to see. I'm just trying to understand why 2 of the speakers would get the DC pulse and not the other 2. I've seen stuff like this before and it defies my 8th training in electrical engineering. I just want to understand it.:p
  19. geshel


    Oct 2, 2001
    Exactly. PBG, give it up. A series/parallel wiring scheme is doubly symmetric, and if one speaker does anything, so will the rest.

    In the above diagram, which is the "path of least resistance", the left branch or the right? Neither. OK, so the current goes through both. Which direction does it go, top-down or bottom-up? I won't answer this because I'm curious to hear what you think. However I'll say it doesn't matter.
  20. I'm going to have to agree with Joris on this one...
    I've never seen anything like you're describing, Psycho.

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