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Thread: Voice coil rubbing question

  1. #1
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    Voice coil rubbing question

    I'm curious how do you know when a speaker's voice coil is rubbing, and what causes it? Also if your simply just reedging a woofer, (no dustcap removal) how can it be avoided? Sorry if its been asked before. I've refoamed an LE-10 this way without problems (luck maybe?, or maybe im just becoming paranoid), and i might be doing a 2214H driver.
    Young, but i love speakers!

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    Senior Member remusr's Avatar
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    VC rubbing can be heard when you lightly push in the cone with 2 fingers placed diametrically opposite on either side of the dustcap. Sounds like scraping. If the speaker has operated with rubbing you will probably be able to see the evidence when you remove the dustcap and gently push the cone forward as grey dusty zones on the inside of the VC. If the spider has to come off or is loose you could also see a polished area on the VC outside windings - insulation is scraped off the wire so NG. If you do see the above you ought to replace the VC via a recone.
    My reconer/refoamer uses deep spacers inside the VC to center the VC when installing a new cone & spider or surround. Others don't use spacers but play a 30Hz or similar signal at low level so the magnet centers the VC in the cap but that may result in a cocked VC that you won't hear until more extreme excursions.

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    I see, then i suppose i might just want to get these ones professionally done by orange county speakers, (ow wallet). is messing up the voice coil when reedging pretty common?, i've done the two le-10's without a problem.
    Young, but i love speakers!

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    Senior Member remusr's Avatar
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    I would get them done by a shop you have a good reference to. OCS is well known but not by me. My guy would be a killer for shipping $!

    So far as VC rubs being a problem I had (2) 2231A refoams I bought on EBay that I had to get reconed because the VC's rubbed and there was major VC damage, possibly due to the refoam effort being misaligned but also maybe due to the prior owner(s) running them with weak/missing foams prior to the refoam? Don't know for sure, just that the bad refoams were done by a hobbyist who claims to be very experienced.

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    haha maybe it was luck when i refoamed the le-10's without voice coil rubbing, but yeah since i dont want to goof these drivers up i'll go OCS, won't hear until more extreme excursions. what do you mean by that anyway? if it got damaged shouldnt it never make another sound anless u repair it. Is there any other good places but cheaper down near southern california? its 90+11 tax$ for a pair of 12" jbl woofers, though thats good pricing anyway and probably better then alot of places in other states.

    In one of the threads Titanium Dome got em refoamed for 30$ each,
    http://audioheritage.csdco.com/vbull...ead.php?t=9797
    i noticed on http://www.donramon1.com/contents5.htm donramon's website it still says 30$, hmmm... I'll try to email them too

    Ok, just got email from them and its 35$ to refoam a 12" JBL, looks like they honored that 20% less then other competitors hehe, this will be my first entry into JBL audio other then the L77 i had (the HF isnt working so i still cant judge it, but i know i liked the LF very much)

    Cant wait till i bring home the L100T once i get them refoamed, they look like a good pair of speakers to my eyes.
    Young, but i love speakers!

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    Senior Member remusr's Avatar
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    Full-depth spacers will ensure the VC former (and the cone itself) is centered and parallel for its full depth. Using a 30Hz tone to generate magnetic centering fields when you glue the spider and/or surround should center the VC at the resting mid-travel point but the VC & cone may in fact be "cocked" and then drive in and out at an angle with more extreme excursions. And that's the rub.
    A JBL 15" aftermarket (MWA) refoam up here is $80CDN, aftermarket 15" (MWA) recone is $170 and official JBL recone is a bit under $250 per published JBL price sched. JBL apparently does not sell refoam kits. My repair dude said he prefers the MWA aftermarket recones over JBL recone kits for reconing 2231A/136A's as JBL only has the the 2235H recone kit that has 1-step stiffer spider than the 2231/136 (20Hz vs 16Hz Fs) and he has had problems vertically centering some JBL kit VC's in the gap. With the MWA he can swap spiders for the softer JBL-equivalent one and ensure the VC is centered per JBL specs. JBL has had several suppliers so maybe that problem is gone as the last JBL kits went well for him.
    Although MWA told him they are tested to be equivalent (same flatwound wire, former, cone material, etc) the MWA foam 1/2 rolls are a smidge smaller diameter with a bit smaller pore size but feel to have the same stiffness. A previous thread here has had strong opinions voiced on JBL vs aftermarket by several reconers on the site. I don't know, have had it done both ways and found that MWA is cheaper and works the same on music so far as I can tell. BUT I expect my woofer tester soon and will know more then, altho maybe I'm better off now!

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    Moderator / Treasurer/Marketplace Czar boputnam's Avatar
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    There are some pointers on how to center the VC when doing a resurround, here: Resurround Step-by-step
    bo

    "Indeed, not!!"

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    Quote Originally Posted by boputnam
    There are some pointers on how to center the VC when doing a resurround, here: Resurround Step-by-step
    I used the 30hz signal method with the resurrounding (tech term?) of my 4425 woofers and it worked quite well. This meant that I didn't have to break into the dust cap to shim - less chance of something going wrong. Of course, this won't help much if there's a weak spider around the voice coil.

    Also, I did a frequency sweep of the woofers after they were reinstalled to make sure that I'd tied down the foam surround well enough not to have loose pieces buzzing.

    Cheers,

    David

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