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Old 14th July 2012, 06:39 PM   #1
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Default Voice coil centering technics during refoam

Anyone a speaker refoam/rebuild expert? I am curious about voice coil centering technique's during the refoam process?

I recently had my dynaudio woofers refoamed and I spent a great deal of time searching the web for experts. with a conventional woofer, most shops cut the dust cap off and place shims around the voice coil to align it while gluing the foam in place. With Dynaudio woofers you can't do that as the cone/cap is all one piece. one shop told my they just cut the dome out and glue in a felt cap! ugh!

So after much searching It was suggested to me that a certain company had a proprietary method of "electrically" centering the voice coil. this interested me. But by the time i got around to being able to ship the woofers, the shop no longer wanted to do Dynaudio woofers! I ended up using a local shop and well...they work, and i guess that's what counts but i wasn't exactly impressed with there work.

After more web searching and watching many youtube videos on refoaming, it seems that this "proprietary" electrically centering process is probably nothing more than applying a low frequency signal to the woofer while manually manipulating the woofer foam into place so the voice coil doesn't rub. not exactly rocket science. but not exactly perfect either.

SO, I am curious if anyone knows of any special techniques new or old that this company that shall remain nameless, might have been using??

I'm curious how Dynaudio actually does it?? I would love to see how that's done!

Zc
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Old 14th July 2012, 07:58 PM   #2
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Dunno how Dynaudio do it, but my method is by using long shims that protrude past the spider, (which is not glued to the VC, just loose), fixing down the surround firmly, glue the spider to the basket all the way around, then let everything set up. Then you push the spider into place, and tack to the VC in a few spots with superglue. Let that set up, then carefully slide out the shims using long nose pliers and run a bead of glue around the spider and VC, covering all the tacks. It's long winded, fiddly and fussy, and you need to think about how you access everything before you start out, but it can be done.
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Old 14th July 2012, 08:06 PM   #3
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when refoaming you don't have that option as the VC is already glued to the spider! but that is an interesting technique! never heard of anyone putting the shims on the outside of the VC like that!
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Old 14th July 2012, 08:10 PM   #4
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The only other method I've heard of beside shims is what you already mentioned; playing a low frequency tone (~30Hz) while the glue is setting.
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Old 14th July 2012, 08:17 PM   #5
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Quote:
Originally Posted by Zero Cool View Post
when refoaming you don't have that option as the VC is already glued to the spider! but that is an interesting technique! never heard of anyone putting the shims on the outside of the VC like that!
Sometimes you just have to make things up as you go along!

I missed the bit about refoaming, not something you do a lot of in the pro world.

If the spider's still attached, then that actually does most of the support and spacing. I'd just clean off the old surround and glue with acetone, glue all round to the cone and let it set up, then tack to the basket in a few places, run some 10Hz test tone, and if there's no rubbing, glue it all down. Sometimes you can overthink these things.
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Old 14th July 2012, 08:48 PM   #6
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AHHH HAAA At 5:51 of this video the secret is revealed!!!

Dynaudio Promotion Video Part 3/3 - YouTube

thin piano wires are put through tiny holes in the cone where the VC attaches to center the VC in the gap. once the glue has dried, they remove the thin wires and glue the tiny holes shut! Magic..or not so much LOL! good old fashion mechanical alignment! no special jigs or tools needed!
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Old 14th July 2012, 09:46 PM   #7
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I've used the LF tone method where removing the dustcap was awkward: Glue the surround to the cone and let it set up a bit. Take care to center it on the cone. Often the old glue line can be a good guide.

Put your bead of glue under the outer surround. Before it starts to firm up, feed an LF tone into the unit that will give a good excursion, say, 1/2" or more peak to peak. Then shift the whole assembly left until it starts to rub, then right until it starts to rub. Note the positions and split the difference. Next shift up to the rub point, down to the opposite rub point and split the difference. Make sure to clamp the surround down so that it will dry with no gaps and make sure it doesn't shift once best centering is found.

Its pretty easy once you try it and I've never had any units that didn't turn out well and play to high excursion without rubs.

David S.
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Old 14th July 2012, 11:48 PM   #8
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When I read about this companies "proprietary" process, i had initially assumed it was something like klipple analysis or some way of measuring the voice coil electrically to be able to align the coil in the gap. I was willing to pay the high price the company charged plus shipping if this had been the case. but once they decided they did not want to do Dynaudio woofers anymore and after a bit of discussion i really got the feeling that they were just doing the 30hz tone routine.
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Old 15th July 2012, 01:27 AM   #9
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What model woofer do you have?
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Old 15th July 2012, 01:28 AM   #10
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24w75's
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