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Speaker buzz surgery -- anyone have experience?

Discussion in 'Shock Brother's DIY Amps' started by King Fan, Mar 1, 2021.

  1. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    I'll try to attach a sound file. Meanwhile: My 6G2 started to buzz, especially on certain notes. After much tweaking, testing, and tightening, tho, I found out this new buzz was from the speaker — a used ALK1028. It does it sitting on the floor, in different rooms, with different guitars and cables, and it does it moved to another amp and cab. Frankly, I’m glad it’s not the chassis (a loose wire behind the board?) or the cab ($$$).

    So in the recording you’ll see it is almost as loud (and a lot more prominent) on faint harmonics as on hard-hit bass notes. (It helps to play the file loud through good speakers).

    Now I can’t hear an *obvious* rub when I deflect the cone with my thumbs. The fact it's there even with faint harmonics, and that it's louder at certain frequencies, must say something. Is it possible to have a voice coil problem and not hear a rub when deflecting the cone? I wonder about a chunk of loose glue or paper in the voice coil gap. So I read the late great Ted Weber's Q&A on a possible fix (quoted below). He includes re-forming the voice coil, which sounds, um, tedious if not risky. But could I just cut out the dustcap like he does and try to blow out any debris?



    Ted said:
    "Lay the speaker on its back with the cone facing up and with a scalpel, carefully cut out the dustcap, leaving about 1/16″ of dustcap where it is glued to the cone. This is important because the voice coil wires pass through this point and you want to make sure you don’t cut them. Next, use a vacuum cleaner or clean, dry pressurized air to suck or blow the dust and other debris out of the gap. If you hold the speaker upside down with the cone facing downward it will probably help getting the dust and debris out. Next, take a 3×5 index card and cut it into a strip that is the correct length so that you can form it into a circle and stick it down into the gap between the inside of the voice coil and the outside of the pole. This will help form the voice coil back into a circle. Next, lay the speaker back down on its back. Take a Q-tip or small paint brush and dip it into a bottle of acetone (finger nail polish remover). Spread a small amount of this acetone on a couple of the rings of the spider, which is the brownish/yellow corrugated disk attached to the backside of the cone at the base of the basket. Next, place a jar lid or other disk on the cone where the dustcap was and let the speaker set overnight. The lid or disk will prevent dust from getting into the gap overnight, and the acetone causes the spider to relax and reposition slightly, thus repositioning the voice coil. The next day, remove the lid and the index card strip and see if you still have a rub. If you do, try the acetone again, same procedure. If, after a couple of tries, it seems hopeless, then professional reconing is the only solution."
     
    Last edited: Mar 1, 2021
  2. muscmp

    muscmp Tele-Afflicted

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    i would first try putting the speaker back 180 degrees and give it a while. i've had situations twice like yours. the first time turning the speaker worked. the second time, the rub was too much and had to have the speaker reconed.

    some people have found that gently pressing, evenly on the cone with both hands may help recenter it. it hasn't worked for me.

    p.s. i just got back a jbl 4301 woofer that i had reconed and it really shows the rub on the voice coil.

    play music!
     
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  3. Wally

    Wally Telefied Ad Free Member

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    I have removed a small blob of solder from a new speaker in a little made in Asia solid state amp before. Hold the speaker with the face of the speaker pointing down and have it near your ear. Can you hear an object rolling/bouncing around when you shake or move the speaker? If so....try this. Cut a small opening in the dust cover, hold the speaker over a larger clean surface, turn the speaker upside down and see if you can get the object to come out. Yeah, I like to see the results so I know I have achieved something. If you get something out, hook the speaker up and see if the noise is gone. If so, smooth opening in the dust cover out and do a repair...white glue and paper towel. if you want to remove the whole dust cove, then I would suggest using a vacuum instead of blowing into the gap. Warning....do not let the vacuum’s suction get a hold of the cone...maintain a gap. You might want to check around the edge of the cone on the backside of the cone to see if there is debris there.
    Also, I do not use thumbs to press a cone for that rub test. I was taught to use an equal number of fingers placed uniformly around the cone to press and release the cone’s movement for that test.
     
  4. Boreas

    Boreas Friend of Leo's Silver Supporter

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    I agree. Try placing the amp face down and tapping around the cone to remove any debris. Then play it a little while face down - not too loud. Then see if you note any change. If it is still there, consider a recone or replacement.
     
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  5. schmee

    schmee Doctor of Teleocity

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    I have not successfully fixed a buzz. It seems a buzz is often in the low A to C range IME.
    There's also a scheme of wetting the spider with acetone to loosen and re-center it and allow the voice coil to shift in the gap a bit.
    The problem is you dont know if the VC is:
    - out of round,
    -off center or
    -if there is debris in there.

    If the speaker was good while you had it, I doubt debris got in with the dust cap in place.
     
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  6. Nickfl

    Nickfl Friend of Leo's

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    I'll be interested to hear if you manage anything that works short of reconing the speaker. I've got a Weber 10 inch sig alnico that did that out of the box. Not as bad as the one is your clips, but still bad enough that I don't want to use it in anything. Unfortunately I had it sitting in the box for almost a year before I realized it was defective and when I emailed Weber they never even responded.

    One of these days maybe I'll try that reforming the voice coil with acetone trick or try my hand at reconing but I can't quite bring myself to do either yet because I'm so annoyed at having been screwed over on the brand new speaker in the first place...
     
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  7. Boreas

    Boreas Friend of Leo's Silver Supporter

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    Yeah, sometimes it is corrosion or a bent frame.
     
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  8. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    Good thoughts, Wally, thanks. Yeah, fingers on the cone, thumbs on the frame feels safer. And yes, you're right, in fact there was a faint rattle when shaking the speaker 'upside down' -- it went away after some shaking, tho, and the speaker still buzzes. And yeah, good idea on checking the edge of the backside -- I have a buddy who found a tiny magnetized washer that would cling to the basket when the speaker wasn't playing.

    I may try your 'simple surgery' -- and if I do I'll for sure observe your caution not to let the vacuum cleaner get hold of the cone!!! Re-cone, yes, de-cone, no.

    For those who doubt newly-arrived debris, I think the theory is that a glue or paper or solder scrap (or wire -- thanks, @Peegoo ) works loose over time and starts bouncing around in the gap. Ted's surgery answer quoted above actually involved a '62 Princeton...
     
    Last edited: Mar 1, 2021
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  9. Peegoo

    Peegoo Poster Extraordinaire

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    Remove the speaker from the amp and have someone hold it by the magnet while you play.

    Still buzzing? That will confirm it's the speaker.

    Give the speaker a few hard shakes and listen for rattles.

    Years ago I had a small 1x10 combo come in with a buzz at certain frequencies, and heard something under the center dust cap. I sliced it off and discovered a 1/2" length of braided tinsel wire loose atop the magnet. It had been left in there when the cap was originally glued on.

    Another possible cause of a rattle is something loose under the spider.

    Make sure the rivet that holds the little wire marshaling board (the card with the spade/solder terminals) is tight on the basket. If it's loose, you can tighten it up by placing a drop of CA at the edge of the rivet. The CA will draw into the gap and solidify the connection. Do not beat on the rivet with a hammer because it's too easy to deform the basket and cause a voice coil rub.
     
  10. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    Hmm, is this a clue, or do all speakers sound like this when tapped? It's subtle, but I hear a slight rattly echo on each tap...

     
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  11. Boreas

    Boreas Friend of Leo's Silver Supporter

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    Difficult to say. It could just be the cone flopping about, but it sounds like the voice coil is rattling.

    If you place the speaker cone-up and EVENLY and carefully move it up and down, it shouldn't make much noise and move smoothly. If it scrapes and scratches you either have foreign material in the coil or the coil is deformed.

    Unless you feel like tackling a re-cone, I would start saving for a replacement speaker. May want to go new this time.
     
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  12. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    You're so right. In fact I ordered a new speaker yesterday before I posted this today. I kinda figure if I could make this one buzz-free, I could sell it on in good faith; otherwise it's "for sale -- best offer -- needs re-coning" -- not much return on effort there. :D

    And yeah, new. I've been through a fair series of speakers on this amp, which never happened to me before. Though I liked this speaker, I've always wanted to try one other model. In his Q&A about the '62 Princeton speaker, Ted ended with this: "As far as using the speaker, if you plan to use it regularly, at high volumes, I would suggest packing the original away and install a replacement speaker. (We recommend the 10A125 for this amp)." :)
     
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  13. Wally

    Wally Telefied Ad Free Member

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    Yes, recentering the cone in the gap as described in the Weber quote above can work when there is a voice coil rub. Ime, one will have to hear the rub if this is to be tried.
    As for that noise with the tapping experiment, that is odd, imho. I don’t know that that is coil rub...especially if you are not getting rub with the depressing/release of the cone. It sounds like something is a bit loose. Is the surround in good condition? Is there any lifting of a gasket anywhere? I just tapped a few cones, and I don’t get anything like that.
     
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  14. Boreas

    Boreas Friend of Leo's Silver Supporter

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    Sometimes the spider can tear away from the cone, but I have never run into that if the cone wasn't abused or torn.
     
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  15. Wally

    Wally Telefied Ad Free Member

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    King Fan tells us this is a used speaker. If purchased used, one never knows what one is buying and to what tests it has been put.
    I would be looking at everything...surround, spider, joints on everything including the dust cover...and voice coil leads. If worst comes to worst, I might dope the surrround.
     
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  16. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    Yes and yes. I *have* had some bad luck with used speakers. My all-time fave speaker came used, but I got that from a trusted TDPRI'er. :) And as you can see from the video, I got this one out in the sun and gave it a thorough inspection. Nothing to see anywhere. Dust cap surgery may lie ahead... but I agree, Ted's method of reforming the voice coil may be a bridge too far. He also mentions later in the Q&A another fairly radical surgery for when the magnet assembly comes loose somehow. Again, no thanks.
     
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  17. Boreas

    Boreas Friend of Leo's Silver Supporter

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    Do you play this amp loud and hard? You may have melted/deformed the coil. I think it is time to invest in a new one. But before you trash it, you may try putting a small blob of silicone on each of the lead solder joints on the cone itself. Sometimes they will rattle.
     
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  18. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    Good question. Actually, I *don't* play it loud and hard. Doesn't mean the speaker's prior owner didn't though.

    Still, since the buzz developed on my watch, it's one reason I vaguely suspect a small chunk of junk working loose due to time and age more than overheating the voice coil. But yes, as I say, a new speaker was ordered right after my (tediously tiresomely annoyingly complete) tests confirmed, to my surprise and relief, that all I needed was a new speaker, not a new cab or circuit... Funny how the least of various evils can start to look almost like something good. :)
     
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  19. Speedy454

    Speedy454 Tele-Holic

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    I bet this one had the frame slightly bent in shipping. Even a re cone won't fix a bent frame. Considering how small the clearance is between the voice coil and the magnet and the center post of the magnet structure, it doesn't take much tweaking of the stamped steel frame to cause the voice coil to rub.
     
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  20. Boreas

    Boreas Friend of Leo's Silver Supporter

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    You can even ruin a speaker by tightening the screws unevenly, or mounting it to a baffle that may warp and distort the frame. A good habit is to tighten the screws in a pattern like auto wheels.
     
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