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How to test for blown speakers?

Discussion in 'Amps and Cabs [BG]' started by seansbrew, Jul 4, 2004.


  1. seansbrew

    seansbrew Supporting Member

    Oct 23, 2000
    Mesa AZ.
    What is the easiest way to rule out a blown speaker? I noticed a buzz when I was practicing today and want to rule out a blown speaker. I know the buzzing can be something in the room so I am not overly concerned yet. I took the grill off the front of the cab and looked closely with a flashlight at each speaker and did not find any visual indications. I also pushed ever so lightly on each speaker to look for a tear, I found nothing. There was a lot of dust and even a spider nest or two so I dusted off the speakers and thought I would check the screws that hold the speakers. It turns out that half of them things were loose bye about an eighth of a turn or so. So I tightened everything up and put the cab back together and will have to wait to test it because baby went to sleep. :oops: But if anyone has a surefire way to tell if a speaker is blown, please post it.
     
  2. I remember using a battery method of testing. Connect one end of an instrument cable to the cab, and then connect the other end to a 9v battery (tip on one side, sleeve on the other). All the speakers should pop out when this happens (and by pop out, i don't mean that literally, just a small movement). I don't think a blown speaker will pop out, not sure though. :rolleyes:

    Hope that helps.
     
  3. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    Blown speakers usally don't work at all, so the bettery test is a good one.

    When you pressed gently on each speaker (hopefully you had your fingers spread evely around the cone area), did you hear of feel any any scraping? If so, the voice coil is rubbing on the gap, which can be caused by several things (burnt bits, a hard hit knocking everything off centre). In either case, you're looking at a recone.

    If there was no scraping, chances are the speaker is fine.
     
  4. If you do the battery trick, make sure to only press the cable onto the battery for a second and dont hold it on there. I have heard that this can be bad for the speaker.
     
  5. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    Well batteries supply a DC current. And Speakers are not designed to handle DC. However, a 9v battery doesn't produce anywhere near enough power to give the speaker any trouble.

    On the other hand, if your amp was faulty and suddenly started sending your speaker DC current, there could be trouble. Basically if the speaker is locked into position for long enough, and your signal is carrying enough voltage (or Watts), the voice coil will heat up quickly because th spekers in-and-out movement is no longer there to help expel heat from under the dust cap. Have you ever noticed that most dust caps are made from a porus material? Either that or you'll find the speaker has a hole at the back usually in the middle of the magnet? Now you know why.
     
  6. seansbrew

    seansbrew Supporting Member

    Oct 23, 2000
    Mesa AZ.
    Ok I was finally able to test my cab out and it's fine. The funny buzz/ vibration went away. I think the maintenance I performed on the cab must have done the trick. Welll, now I know maybe once a year I will take the cover off my cab and make sure all of the screws are tight and not working their way out. Sort of like the manitenance one would perform on a head. Thanks for all your help everyone; man I dig TB. :)