Psst... Ready to join TalkBass and start posting, make new friends, sell your gear, and more?  Register your free account in 30 seconds.

one speaker moving more than others

Discussion in 'Amps and Cabs [BG]' started by tolas, Aug 29, 2005.


  1. tolas

    tolas

    Mar 16, 2005
    For a short history. I purchased a Bergantino NV610 from a place in detroit michigan. When I got it, it had one of the speakers replaced with a different looking speaker, and it sounded blown at that.

    Apparantly the original speaker had blown, and they put an ampeg 10" speaker in there while the other one was getting re-coned. After speaking with the shop and Jim Bergantino, I finally got a new speaker sent to me direct from Jim himself.

    I have since installed it, and it sounds damn fine, but I can see this speaker moving NOTICEABLY more than the other speakers. I would say the excursion is at least twice the other speakers. Now it's possibly true that this cab blew both the original speaker and the replacement ampeg speaker in this one location. And frankly i'm scared it's going to happen again.

    what could be causing this, and what can I do to fix it?
     
  2. If I didn't know better, I'd say the replacement speaker was the wrong impedance...but surely Jim Bergantino knows what speakers go in his own cabs so I'm clueless.
     
  3. Maybe it just has to be ,broken in': breaking in changes some things in the speaker. Even the resonance freq can change; this could cause the speaker to make big excursions now but 'cure itself' later.
    It could also be something else...
     
  4. Eric Moesle

    Eric Moesle Supporting Member

    Sep 21, 2001
    Columbus OH
    Possibly a wiring error as well. Retrace EVERY connection within that cab between all of the speakers. Check the overall impedance with a meter. Also put a 9volt battery across the speaker cable to see if every speaker goes in or out at the same time, if they don't you have a phase issue.
     
  5. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    I suspect the driver is wired out of phase and is literally displacing as much as the other five drivers combined. In addition there's got to be a lot of phase cancellation happening, and it's only the 5:1 in phase/out of phase ratio that's allowing the box to work at all. The wrong impedance could be a problem but would only be so obvious if the original drivers were at least 16 ohm and the replacement 4 ohm. Could happen,though.
     
  6. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    A polarity issue, actually.
     
  7. tolas

    tolas

    Mar 16, 2005
    well i've only had the one speaker out and i hooked it up the way the other speaker was hooked up, but perhaps the shop hooked it up wrong. It had the "red striped" cable going to the negative terminal. Is this standard?

    Perhaps i'll take each speaker out to check the wiring, but i'm a little nervous of stripping the screws or worse... putting a screwdriver through one of the speakers.

    Any other ideas. Could it really just be the "break-in" factor? I always though that if it was wired up wrong, the speaker would move opposite of others, not more than the others. Plus when I put my ear right up to that speaker it sounds fine, just a little brighter than the others for some reason.

    As for the 9v battery.. please explain what I should do. Just touch it to the metal end of the speaker wire with the other end plugged in to the cab, and make sure all the speakers move the same way?

    thanks for everyones help
     
  8. Eric Moesle

    Eric Moesle Supporting Member

    Sep 21, 2001
    Columbus OH
    Speaker "break-in" would work the opposite of what you describe: the new speaker being stiff, and loosening after broken in. If your new speaker is jumping more than the others, it is not a break-in issue. It will not move LESS once broken in.

    As for the battery trick, place the sleeve of the plug on negative, the tip of the plug on positive, with the other end of the plug inside the speaker jack on the back of the cabinet. Just do this for a second or two. All of the speakers should go in or out together. If one goes opposite of the other speaker, its polarity is reversed, and you should reverse the plugs on that speaker only, to match the others. My bet is that this is your problem.

    Good luck!
     
  9. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    Nope that's back to front. Red = Positive and Black = Negative. And all speakers must be wired up the same way.
     
  10. Passinwind

    Passinwind I Know Nothing Supporting Member

    How about just reversing the leads on the one speaker and seeing what happens? If the problem goes away, you're done.
     
  11. The battery trick will tell you instantly if the one speaker is miswired, without having to take the speaker out and reverse the wiring to try it and risking screwdriver through the cone/stripping screws.

    Randy
     
  12. Passinwind

    Passinwind I Know Nothing Supporting Member

    Agreed, but he asked for other ideas. ;) If the speaker is miswired, he's still gonna have to deal with the scary process of unscrewing it again too. I've taken to using allen head bolts for mounting drivers in my own cabs, or hex head ones for the bigger sizes. It'd take extra effort to make one of those slip off. Might be easier to strip 'em though...
     
  13. Soemtimes speaker leads can be mislabelled, I've heard of magnets going into the magnetizer upside-down.... :D
    So the battery trick would be good for identifying an odd speaker.
     
  14. tolas

    tolas

    Mar 16, 2005
    it was definitely the polarity issue on the one speaker in question. The battery trick showed me this. I can't believe how much louder it is now. Finally it sounds like what i've heard the bergs are supposed to sound like. I'm so happy now. :hyper:

    thanks for everyones help.

    - john