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Speaker recone or replace???!?!?!

Discussion in 'Amps and Cabs [BG]' started by iplaybasstexas, Sep 28, 2008.


  1. iplaybasstexas

    iplaybasstexas

    Apr 5, 2008
    DFW
    I have issues with my Ampeg.
    I turned on my amp today and the sound was very "electric-synthy" and horrible sounding. I examined my spakers.

    All of the speakers were perfect except one.
    it felt "hard" and nonmovalbe almost. it doesn't really move at all. when i put my hand as to muffle that specific speaker, it sounded find.

    what do i do?
     
  2. craig.p

    craig.p

    Sep 28, 2008
    New Hampshire
    The voice coil overheated and went out-of-round. Now the coil is scraping the magnet slot, rather than floating inside it as it was before. If it were my amp I'd just contact Ampeg and have them ship you a re-coned speaker. There must be some "core value" (trade-in) on yours. In the meantime, you may be able to limp along with that speaker disconnected (but still in place). Depends on what cab you have & how it's wired. If I recall correctly, an SVT cab I had back in the 1970s had eight 32-ohm speakers wired in parallel, so taking one out of circuit would have been a trivial matter; the 4 ohms wouldn't have risen by much. Which cab do you have, what's its nominal impedance, and can you pull the bad speaker and let us know what its impedance is on the magnet label?
     
  3. iplaybasstexas

    iplaybasstexas

    Apr 5, 2008
    DFW
    Its an Ampeg SVT410HLF.

    Well, i don't know much about wiring...but if its a simple (+) (-) wire connection thing, then i can do that.
    the 410 is 4 ohms.

    so are you sure thats the reason? how does that make the speaker hard and nonmoving?
     
  4. craig.p

    craig.p

    Sep 28, 2008
    New Hampshire
    I can't think of any other reason other than the cab fell out of a 3rd story window but only one voice coil took the hit. That would be nuts.

    "Speaker hard and non-moving..." Let me try again. The voice coil normally "floats" inside a magnet gap. The tolerances between the voice coil and the magnet metal are *very* close. Okay... voice coil overheats and warps. Doesn't have to be much of a warp. Now part of the voice coil's outer circumference scrapes against the magnet gap in which it really should be free-floating. There's your resistance to movement. Also it is possible that the magnet has magnetically "glued" the voice coil to itself, which would account for it being hard to move.

    Ok, cabinet is 4 ohms. How about the speaker itself? Pop that baby out and see what it says on the magnet. I'm hoping you'll tell us 16 ohms. From there we can tell you what to do.

    Whatever the answer, you are going to have to be *very* careful volume-wise with one driver out of the circuit. If you absolutely must play at the volumes this rig was played at the last time, you really ought to rent something until you get your new speaker in.

    I am of course going on the assumption that this failure was caused by overdriving.

    Just thought of another reason -- you could have overdriven the suspension and now the speaker is "parked" too far forward or too far back. Subharmonics can do this and so can excessive bass boost. Either way, the speaker's bad and it has to come out.
     
  5. iplaybasstexas

    iplaybasstexas

    Apr 5, 2008
    DFW

    taking out now.

    and i'm guilty on both charges.
    My mesa drives this cabinet pretty hard and i think it overdrives the watts of the cabinet.

    and my EQ is definetly more on the bass boost. I love the lows.
    subharmonics, define what those are?
     
  6. iplaybasstexas

    iplaybasstexas

    Apr 5, 2008
    DFW
    speaker is out.

    so, the label on the speaker says 4 ohms.

    and
    also,
    the voice coil (orange one right?) looks bigger than its supposed to be.
    doesn't allow for much movement.

    AND

    the magnet is almost fully separated from the metal frame of the speaker...is that bad?
     
  7. craig.p

    craig.p

    Sep 28, 2008
    New Hampshire
    > subharmonics, define what those are?

    It's the extremely-low-frequency stuff that is so low you can't hear it. It makes your speaker cones dance around. Transistor-output amps are far more prone to this (unless they're built with a subharmonic filter) because they do not have a transformer in their output circuits. Transformers naturally roll off subharmonics. With transistor outputs you're basically relying on the power supply to "give up" when high-power subharmonics come along, but unfortunately some power supplies are so beefy and well-made that they see high-current demand at, say, 2 Hz, and they say, "Oh, you want lots of amps that close to DC? Hey, no problem, man!" The current gets delivered to the voice coils, and the speakers get delivered to the undertaker's.

    In your case, it was the bass you could not hear that caused the damage. You should invest in a subharmonic filter, and a good steep one, like 18dB/octave or steeper. Or watch the eq. You can go overboard adding bass at the instrument pot, then adding more with the bass tone control, then adding more with x-band EQ, then adding more with effects -- before you know it you've got 20x more power going to subharmonics and speaker destruction than you to do making sounds you can actually hear.

    But I guess you know that by now, eh? ;-)
     
  8. craig.p

    craig.p

    Sep 28, 2008
    New Hampshire
    4 ohm speaker x 4 in a 4-ohm cab means series/parallel wiring. I was hoping you'd say 16. Oh well...

    In this particular configuration I would recommend you *not* band-aid this thing, but wait for the replacement driver instead. This is because of all the added current the blown speaker's "series partner" would have to handle if you were to bypass it. You're already on the edge as it is, and you'd probably just wind up smoking another voice coil. Best thing to do would be to rent something for the short term.

    I know, not what you wanted to hear...

    Any local shops around that might be able to pull a driver from a used cab for you? Shouldn't be that $$$. You could still get the bad driver reconed & keep it as a spare.
     
  9. iplaybasstexas

    iplaybasstexas

    Apr 5, 2008
    DFW

    my amp is half tube (Mesa Big Block 750).
    i will look into one. can you give me an MF link to a good one?

    and as far as EQing, etc., i use no effects and my bass "hump" in the EQ isn't that large. With Gain-Bass-Mid-Freq.-Treble, my settings are 7-7-5-10-7.

    also, do you think the other four speakers will be like this?
    What caused the magnet to separate from the speaker frame?
     
  10. craig.p

    craig.p

    Sep 28, 2008
    New Hampshire
    BTW, I read what you said about the appearance of the unit but the best thing to do is compare with a unit that you know is good, i.e. pull another speaker. That's really the most reliable way to tell.

    Also, you can not see the voice coil. It is "buried" (enclosed/floating) inside the confines of the magnet.
     
  11. iplaybasstexas

    iplaybasstexas

    Apr 5, 2008
    DFW
    i don't think this is a recone issue...

    i'll see if i can find another ampeg speaker around. its needs to be 100-150w, which shouldn't be that hard to find.

    and sorry, my bad. the speaker is 32ohms.


    i do have another cabinet that handles tons more wattage.
    Do you know what a sine wave is?
     
  12. iplaybasstexas

    iplaybasstexas

    Apr 5, 2008
    DFW
    well i can now...because of the separation of the magnet, there's a orage-colored cylindrical object in the magnet that i can see.
     
  13. craig.p

    craig.p

    Sep 28, 2008
    New Hampshire
    If the magnet truly is separated from the frame, then the speaker was defective to begin with (or someone dropped it on the concrete at the factory before he installed it) and now you can dial all that bass back in, LOL...

    Not sure where to get a sub filter other than in some rackmount EQs. Maybe some other folks can help you there. I have to believe they're out there. I used to build them into teeny weeny Bud boxes 25 years ago but I don't do it any more (got other junk going on, way too busy already, etc. etc. etc.......)
     
  14. ErebusBass

    ErebusBass

    Feb 20, 2008
    Madison, WI
    I know nothing about your amp. If it has an x-band eq, turn the lowest frequency down, then turn the next lowest frequency up. It'll still sound nice and bassy, but will give your speakers a little bit of a break and reduce subharmonics. I always cut anything below about 30 hz or so.
     
  15. craig.p

    craig.p

    Sep 28, 2008
    New Hampshire
    > well i can now...because of the separation of the magnet,
    > there's a orage-colored cylindrical object in the magnet
    > that i can see.

    Yikes!

    Someone screwed up and it wasn't you. Speaker was built wrong or a weld let go or someone dropped it or whatever. But I'm 99% sure overdriving wouldn't detach a magnet from a frame. And with such a catastrophic failure, if the amp had caused it, at least *something* would've happened to the others.

    Not your fault.
     
  16. iplaybasstexas

    iplaybasstexas

    Apr 5, 2008
    DFW

    the front panel of my mesa looks like this:

    [ GAIN---BASS---PASSIVE MID---ACTIVE MID---FREQUENCY--
    TREBLE-MASTER]
     
  17. iplaybasstexas

    iplaybasstexas

    Apr 5, 2008
    DFW
    so what should i tell Ampeg when i call tomarrow?

    and i took out the another speaker and it looked fine.
     
  18. craig.p

    craig.p

    Sep 28, 2008
    New Hampshire
    If the speaker is 32 ohms, and if the rest of 'em are also 32 ohms, and if they're all connected in parallel (which would make most sense), then you have an 8-ohm cab. I would check the labels on the rest of the speakers to be sure of what exactly you have there. Is this a used cab? If it's marked 4 ohms and it's used, my guess is someone blew one or more original speakers and replaced same with speakers out of an 8x10 SVT cab. Just conjecture on my part based on what you've told me, in league with my usual suspicion and distrust of human behavior in general. :-/

    Or if it's a new cab maybe the factory just marked it 4 instead of 8. Which would get humanity off the hook. For the moment.
     
  19. iplaybasstexas

    iplaybasstexas

    Apr 5, 2008
    DFW

    well, here it is.
    the speakers say "4 ohms" on the label.
    but on the black stuff of the speaker, it has the numbers 32 then a space and some more numbers. it doesn't say 32 ohms, but logic told me 32.

    So, by the label, they are all 4 ohm speakers....
    which doesn't make sense!?
     
  20. craig.p

    craig.p

    Sep 28, 2008
    New Hampshire
    WRT what to tell Ampeg, take a pic of the 2 speakers side by side, upload it to Flickr or something similar, get a tinyurl for the link, then give that url to the person on the phone so he can see exactly what the problem is. Nothing like a pic, especially for something as nasty as this.

    Or you can just tell the person that the magnet has detached from the speaker basket but the other 3 in the cab are fine. It's important you stress that the other 3 are ok because that's the real indicator of this particular speaker being built wrong, or dropped/mishandled during final assembly.
     

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