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Blown tweeter?

Discussion in 'Amps and Cabs [BG]' started by ajb, Mar 23, 2006.


  1. ajb

    ajb

    Mar 20, 2005
    I have an Aguilar GS 212 and last night, with the tweeter at about halfway up, I noticed that the tweeter made a distorted sound when I really dug in playing fingerstyle on the G string (I was playing pretty aggressively). The sound was not there when I turned the tweeter off, so if there is any issue I am pretty sure it's with the tweeter. Playing with normal touch everything sounds fine.

    I was playing through a GK 700RB-II head, which as some of you may know has pretty crisp highs. Do I have a blown tweeter, or is the distortion I heard normal? I'm not sure if distortion is the right word; it was sort of like a loose flapping sound, if that makes any sense.
     
  2. billfitzmaurice

    billfitzmaurice Commercial User

    Sep 15, 2004
    New Hampshire
    Owner, Bill Fitzmaurice Loudspeaker Design
    It could be blown, but usually a blown tweeter will sound bad at any volume. More likely the slope of the crossover is insufficient to keep all the low frequencies out of the tweeter, so at high volumes the tweeter cone is moving too far, the same way a woofer farts out with very low notes at high volumes. The easy fix is not to run the tweeter pad wide open, back it off enough to keep the distortion at bay. It's also possible that you're overtaxing the amp, pushing it into clipping, which you'll hear in the tweeter as distortion. The cure for that is to turn down.
     
  3. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
    Another possibility is that horn has a light bulb protection circuit. Those things usually sound distorted and compressed when they kick in, but they're usually acompanied by a burst of light from within the cab. If your back was turned, you may not have seen it, but if your eyes were anywhere near the cab at the time, you should have seen it, either through the cab's ports or even through the speaker surrounds.

    Either way, the solution is as Bill suggested, back the tweet off a bit.
     
  4. ajb

    ajb

    Mar 20, 2005
    Thanks for the responses guys. This is very weird, because last night I noticed that when I engaged the tweeter (not full on, mind you, but about halfway) a loud humming sound began emanating from the speakers, and there was some crackling/static coming out of the speakers. I have also noticed this loud humming sound coming out of the speaker when I run my Aguilar DB 359 through the same speakers with the tweeter engaged, so I don't think it has anything to do with the GK head.

    Turning down the tweeter muted the hum considerably, but did not completely eliminate it. The crackling/static persisted. After some time playing all of this went completely away, including the initial problem I posted about (the tweeter farting out issue). Now everything sounds fine, no hum, no crackling.

    Any ideas?
     
  5. Eric Moesle

    Eric Moesle Supporting Member

    Sep 21, 2001
    Columbus OH
    I thought I had a problem with an Aguilar tweeter several months ago, ordered a replacement diaphragm, and the distorted sound persisted. Turned out it was a creased speaker, NOT the tweeter - even though my ears could have sworn it was the culprit. Usually a tweet cuts out all together if its blown.

    If the troubling sound persisted even when your tweeter was off, then the tweet was just amplifying whatever the problem was earlier in the signal chain. I would suspect your amp, cable, or bass to have been causing the problem.
     
  6. ajb

    ajb

    Mar 20, 2005

    It's not possible that I have a creased speaker as well?
     
  7. ajb

    ajb

    Mar 20, 2005
    Let me clarify: I just bought my Stingray 5, it's a used 1993 model so I took it in for a full set-up, electronics check-up, etc. I don't think it's the bass.

    The GK head is brand new and in fact I just traded it in for a new one, in an abundance of caution, when I first noticed the tweeter farting out problem. So I don't think it's the head.

    Cables? Possibly, but I just got new ones from bayou cables.

    So: Is it possible I have a creased speaker as well?
     
  8. LoveThatBass

    LoveThatBass

    Jun 28, 2004

    I am with Bill Fitzmaurice on this one. It is not your head, it is not your speaker, it is most likely the slope of your tweeter crossover is not sufficient enough. Most are just a 12db (2nd order) or at most an 18db (3rd order). My original was just a 6db slope and I made a 4th order 24db that does quite well for the most part but will still get some distortion if the bass lows are turned up high and at higher wattages at times.
    Yes, if this happens too much at high wattages you can blow the tweeter horn, however it will sound distorted all the time if that were to happen. Your only options are to turn your tweeter down more or get a better crossover unit for the tweeter.
     
  9. Eric Moesle

    Eric Moesle Supporting Member

    Sep 21, 2001
    Columbus OH
    Makes sense, but he said the sound continued when the tweeter was OFF. That, and the fact that Aguilar uses very high quality fourth-order crossovers in their GS series cabs.
     
  10. Petebass

    Petebass

    Dec 22, 2002
    QLD Australia
     
  11. ajb

    ajb

    Mar 20, 2005
    Hey guys, here's an update on the crackling issue I'm experiencing with my GS 212. First off, I can now get the problem to be reliably reproduced. Here's how it happens every time: I turn my amp on, with the tweeter on the cab about halfway engaged, and a loud hum begins to emanate from the speakers. The sound resembles the magnetic buzz you hear around those machines that people put in their backyards to zap mosquitos in the summer (midwesterners out there know the machines I'm talking about). The bass sound is fine at this point, but the background hum is pretty annoying. After a couple of minutes though, I start to hear a crackling coming from the speakers. To my ears it sounds like the crackling sound is coming from the tweeter. The crackling sound then starts to intensify and get progressively more harsh. Then, all of a sudden, the hum stops, and the crackling goes away. You might get a couple of crackles for a minute after the hum stops, but they eventually get real faint and go away. It takes about five minutes of playing to get the humming and crackling to stop. Everything sounds fine from this point forward.

    At this point I've eliminated the bass, the instrument cable, and the speaker cable as the cause. The hum and crackling happen whether I use my Stingray 5 or my jazz bass. It happens whether I use my Sadowsky instrument cable or my bayou cables instrument cable. It happens whether I use my bayou cables speaker cable (which has a speakon that goes into the cab) or my power plus speaker cables (which do not have speakons).

    Tomorrow I'm going to go to Gutar Center to plug my GK head into other cabs to eliminate the amp as a cause. My gut tells me it's a speaker issue, because I had some crackling issues with my Aguilar DB 359. I also had a cut-out/drop volume issue with my DB 359 which I posted about and don't know if this is related because I don't get the drop volume problem with the GK head. But the harsh crackling sound does sort of resemble the sounds preceding the drop in volume when I had the issues with my Aguilar DB 359. I could never get the drop volume to happen reliably though. By the way, Aguilar recently inspected my DB 359 and told me they couldn't find a thing wrong with it.

    So that's the story for now. Any thoughts you guys have would be appreciated.
     
  12. ldervish

    ldervish

    May 22, 2005
    Johnson City, TN
    You could perhaps eliminate either the head or the cab by adding another cab. If the symptoms appear in BOTH cabs, it's source is the amp. Conversely, if the symptom remains only in the GS 212, you'll know the problem lies there.

    Intermittant problems are tough! I've forgotten most of the electronics I once knew, but it seems to me that what you're describing could be a component (or a cracked solder joint) which does not function properly until heated up by current flowing through it. Techs can check for this by spraying components in the suspect section one by one with a chilling spray until the hum/crackle magically reappears when they hit the bad part. Obviously, the circuit must be active when this type diagnostic is run.

    Also, IIRC, turning the tweeter controls down will not shut off the crossover circuit. Instead, the circuit remains active but the signal is "rolled off" or shunted to ground instead of to the speaker driver. More electronically knowledgeable TBers can check me out on that, but I'm pretty sure that's accurate. If there is a bad component on the xover board, it might explain the symptom presence even with the tweeter "off".
     
  13. ajb

    ajb

    Mar 20, 2005
    Is it possible for my speaker to have a cracked solder joint or is a cracked solder joint something that could only be found in the amp?
     
  14. ldervish

    ldervish

    May 22, 2005
    Johnson City, TN
    I am fairly certain that in a high quality cabinet such as yours, a high-order xover would use a PC board with components soldered onto it. So yes, it is possible in the cabinet. I had a satellite decoder which had a solder joint fail after several years of use, and a quick hit with the iron restored it to operation.

    If you intend to resolder those junctions, be sure that you don't overheat the components when you do it - clean the tip of your iron by wiping on a piece of old rough cloth, and with a bit of new solder on it re-heat the soldered joint until it flows, and get off. Or, have your tech do it if you aren't confident in your technique.
     
  15. tadawson

    tadawson

    Aug 24, 2005
    Lewisville, TX
    Bad solder joints can happen anywhere, but I have never seen one create a specific sound, like the buzz you describe. Myself, I would look at the amp - speakers don't create sounds, they reproduce them. On failures, a speaker can only detract from your sound, not create new things . . . . .

    - Tim
     
  16. ldervish

    ldervish

    May 22, 2005
    Johnson City, TN
    Tim, what you say is true, as far as it goes. In this case, there is an electronic circuit inside the speaker cabinet which is designed to alter the amp's signal by shunting portions of it to one of these: the low freq drivers, high freq driver, or ground. So, it is between the amp and the drivers, and IMO could affect what the drivers reproduce. In addition, I think ajb said at the top that he had replaced his original head with another (the GK) and had the problem with both of them.

    "The GK head is brand new and in fact I just traded it in for a new one, in an abundance of caution, when I first noticed the tweeter farting out problem. So I don't think it's the head."

    My bet is something in the cabinet, either a solder joint or a component is failing. It will be interesting to see where the dust settles on this.
     
  17. tadawson

    tadawson

    Aug 24, 2005
    Lewisville, TX

    Yeah, it's called a crossover, is dumb as a rock, and STILL can't CREATE signals that were not fed to it in the first place. As you stated, crossovers direct the signal to the appropriate driver(s), not create them. Unless you play a note that has a fundamental tone like the hum that is described, the speaker can't create it from thin air. And, perhaps I am mistaken, but as I read the post, the noise is there whether the bass is being played or not, and that SCREAMS "AMP PROBLEM" loud and clear . . . .

    I missed the comment about having tried multiple heads. I guess we all describe "hum" differently - for me, that means a constant 60Hz hum . . . . to others, ????


    - Tim
     
  18. greenboy

    greenboy

    Dec 18, 2000
    remote mountain cabin Montana
    greenboy designs: fEARful, bassic, dually, crazy88 etc
    Hi! I'm your friendly amp technician! I live perhaps thousands of miles outside the range of hearing and seeing your amp - even when it's turned up and working! So I've devised this handy questionnaire! In order to help me more efficiently diagnose and repair the problem with your amplifier please respond to the following points:


    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    1. Describe your problem:

    2. Now, describe your problem accurately:

    3. Speculate wildly based on faulty knowledge about almost everything
    just what's the cause of your problem:

    4. Please indicate the severity of your problem:
    A. Minor___ B. Minor___ C. Minor___ D. Trivial___

    5. Nature of problem:
    A. Sounds bad___ B. Sounds really bad___ C. No sound___
    D. Strange smell___ E. Smells really bad twice___

    6. Was your amp plugged in?
    Yes___ No___

    7. Was it turned on?
    Yes___ No___

    8. Did you try to fix it yourself?
    Yes___ No___

    9. If so, did you make it worse?
    Yes___ Yes___

    10. Did you have a "friend" who "knows all about amps" try to fix it for you?
    Yes___ No___

    11. If so, did they make it worse?
    Yes___

    12. Have you read your manual?
    No___ No___

    13. Are you sure you've read the manual?
    Maybe___ No___

    14. Are you absolutely SURE you read the manual?
    No___ I was going to...___

    15. If you DID read the manual, do you think you UNDERSTOOD it?
    Yes___ No___

    16. If yes, explain why you can't fix the problem yourself:

    17. What were you doing to your amplifier at the time the problem occurred?

    18. If you answered "nothing", explain why you think there's a problem:

    19. Are you sure you're not imagining the problem?
    Yes___ No___

    20. Does the clock on your DVD player always blink 12:00?
    Yes___ That's a clock?___ What's a DVD?___

    21. Do you have any electronic devices that DO work?
    Yes___ No___

    22. Do you have an independent witness to the problem?
    (Does not include drummers)
    Yes___ No___

    23. Have you given the amplifier a good whack on top?
    Yes___ No___

    24. Did the amplifier catch fire?
    Yes___ Not yet___

    25. Do you have another amp you can use while you wait to take this one
    to a repair shop like you should have done in the first place?
    Yes___ No, I prefer to be out of commission longer___

    26. Has the foam inside your speaker cabinet caught fire repeatedly?
    Yes___ No___ What's a "cabinet"?___

    27. Has the foam inside your speaker BOX caught fire repeatedly?
    Yes___ No___

    28. If so, did you replace it with an approved dampener?
    No. Enough beer gets spilled in there to keep it safe___
    No. The cat's always whizzing in there after a good scratch on the carpet anyway___
    Yes___

    28. Let me restate this: If so, did you replace it with an approved DAMPING material?
    Yes___
    No. My drummer used all the egg cartons inside his kick drum instead. ___

    ~~~~~~~~~~~~~~~~~~~~~~~~~~~
     
  19. ajb

    ajb

    Mar 20, 2005
    Hello again everyone, thanks for the responses. I have an update. Today I took my GK head to Guitar Center to try and eliminate the head as the cause of the problem. I played the head and my Stingray 5 though an SWR Goliath III Jr. Guess what? No problems whatsover! In fact, I bought the SWR cab because it sounded so good (my sickness knows no bounds). Brought it home and evrything was fine too.

    So I think this pretty much eliminates the amp as the cause of the problem, right?
     
  20. tadawson

    tadawson

    Aug 24, 2005
    Lewisville, TX
    I'd have to agree, yes . . . . unless, for some reason, the other cab was causing the amp to go into oscillation, which would be pretty unlikely . . . . Have you tried the cab with another head? If that works fine too, then, unfortunately, you would be back to square one . . . .

    - Tim
     

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