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Old 23rd June 2010, 07:41 PM   #11
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Your VC repair technique is quite novel and admirable. Getting the VC centered whilst gluing the spider without shimming is a VERY sticky wicket.
Your best bet is a test tone. Good luck!



Quote:
Originally Posted by limono View Post
I'm not sure if I stay on the topic but I'm on the stage 2 of my JBL LE 8 repair saga. I've got a pair of refoamed early black cone drivers. Unfortunatelly the drivers VC's were partially shorted (probably thanks to original owner trying to play music trough the speakers with rotten surrounds and VC's rubbing the magnet gap assy) They measured 1.3-1.5 Ohm instead 5.4 Ohm. Ater entertaining recone options ($202 each from JBL -ouch)and trying to find a nice pair for reasonable money (nope!) I decided to try my old friends trick.
I heated and separated lower suspension from the basket and took the cone assy out . I filled the cup with shellac enough to submerge VC in it when the rest of cone sits on the cup and connected the wires to car batter charger (2 amps) in short intervals in order to heat them up enough to separate from each other and let the hot shellac penetrate and insulate the coil.This primitive method worked OK and now I have 5.4 ohms reading on the coils. I ordered a suitable surrounds and now comes the sticky bit .The alu dust cover part is integral part of the driver and I'd like to keep it intact. It makes shimming the coil from inside impossible. How would you aproach putting it all together ?.Start with glueing the surround to the cone then position it in the basket, clamp it .try if it is not rubbing (play some test signal -music generator) than slowly glue in lower supension section after section lifting it a little and holding the cone in place.Thats my plan but I did not attempt to work on the speakers for years . Regards, L
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Old 23rd June 2010, 08:45 PM   #12
limono is offline limono  United States
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Do you advise attaching foam surround to cones first ? ( they glue to back side of the cone) or maybe gluing surround to the basket and suspending the cone while playing with positioning and trying to attach spider .I'm deliberating on the order or strategy and devise a plan what to do .
Regards, L
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Old 23rd June 2010, 08:48 PM   #13
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I always glue the surround to the cone first.
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Old 27th September 2010, 01:51 AM   #14
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Update...

Since my original post, I've tested about half a dozen foam surrounds from various suppliers. The lowest free air resonance I got was 16Hz. The highest, 25Hz. When the speaker was new, it was just under 15Hz.

Interestingly, the replacement foam that provided the lowest resonance had a somewhat rough surface. These foams also were the only ones to "break in" and drop to a lower frequency after some exercise. All the other foams had a smooth surface, and all were stiffer to various degrees.

The foam that was the stiffest (and therefore furthest from the original) was from a well-known speaker parts and re-build company. The most compliant foam was from just an ordinary vendor on ebay. I got quite a few foams that resulted in a resonance of around 18Hz.

No moral to my story, other than trial-and-error seems to be an unavoidable part of solving this issue. I've played with so foam surrounds at this point, that I can tell by "feel" which are the most compliant even before I test them.
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Old 27th September 2010, 11:46 AM   #15
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Quote:
Originally Posted by Robert1954 View Post
Update...

Since my original post, I've tested about half a dozen foam surrounds from various suppliers. The lowest free air resonance I got was 16Hz. The highest, 25Hz. When the speaker was new, it was just under 15Hz.

Interestingly, the replacement foam that provided the lowest resonance had a somewhat rough surface. These foams also were the only ones to "break in" and drop to a lower frequency after some exercise. All the other foams had a smooth surface, and all were stiffer to various degrees.

The foam that was the stiffest (and therefore furthest from the original) was from a well-known speaker parts and re-build company. The most compliant foam was from just an ordinary vendor on ebay. I got quite a few foams that resulted in a resonance of around 18Hz.

No moral to my story, other than trial-and-error seems to be an unavoidable part of solving this issue. I've played with so foam surrounds at this point, that I can tell by "feel" which are the most compliant even before I test them.
Thanks Robert, but I think the 'masses' of would-be DIY re-surrounders would really like to know who's who with respect to your results. Could you please share here and over at AK.org?
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Old 28th September 2010, 07:42 PM   #16
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From what I was told back in the late 70s the resonance will go lower after some break in period this may apply in your case.
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Old 28th September 2010, 08:37 PM   #17
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Originally Posted by Triodethom View Post
From what I was told back in the late 70s the resonance will go lower after some break in period this may apply in your case.
Yes it will, but not a lot. Perhaps 2-4 hz.
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Old 28th September 2010, 09:02 PM   #18
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True but at 20 hz that's 10 to 20%

Last edited by Triodethom; 28th September 2010 at 09:02 PM. Reason: correction
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