LE-85 Diaphragm Removal and Replacement

[Regis]

I hear what you're saying, yes, I wish I had a lighted workbench, a cleanroom to make my own IC's, etc, etc. But I do own a lamp and magnifier and have some tools. Maybe I'm a lucky sumabitch, but it works fine, sounds good and Dave from NY prepped the motors before sending them (he had removed the diaphragms before sending them out). (I traded the original wax sealed, unopened LE-85's for a pair of undiaphragmed, perfect LE-85's. Add new 16421's and I'm in business.

Maybe I should've called this the "garage-grunge" thread . Just didn't seem as absolutely difficult as what it's made out to be (call it luck). As far as the schematic I looked at an L-300 and a 3133 schematic and unless it's wrong, the black negative input goes to the black wire. Please correct me if I'm wrong.

[edgewound]

Hi Regis...

On Vintage JBL with the exception of the D123,for not-well-known reasons, positive voltage applied to the BLACK terminal will result in outward cone movement, and also diaphragm movement toward the phase-plug of JBL compression drivers. Check this with a flashlight battery and you'll discover this. As long as all network wires, go to the proper colored terminals, all is fine inside the enclosure...but it's backwards outside at the system input. Really, the only time this might be a problem, is if you're using other mfr's speakers in the same room...say for home theater. If this is the case, your fronts and rears will be out of phase....Please correct me if I'm wrong, and I'll research it further.

It wasn't my purpose to offend you in any way, and If I did, I apologize. I posted the rediaphragm process at the request of Mr. Widget.

I don't recall stating that you need a "clean room" to do this procedure, and you also didn't mention that the drivers were were exchanged and prepped by a Pro. Too much info is omitted in these forums....due to brevity... and can result in bad communication . But your thread was nicely done with the photos ...but some critical steps weren't mentioned.

Rock on up to the Summit,

Edgewound

[Regis]

I just have to have some fun with this! Heck, I learned some new stuff from this, especially the out-of-round diaphragm condition that can sometimes occur. Just being humorously sarcastic. The thread was good in that it brought into play a whole lot of information (that unless I didn't search correctly) wasn't available before on this site. So I went with what Steve and I knew.

Thanks to all of you for your thoughts and input. And don't freak on the next thread upcoming, the L-300 bypass cap mod, as I worked on the floor (on a clean piece of large cardboard mind you)! I didn't remove the entire network as I would've had to pull the foilcals and then the L-pads off and then remove the horn again (the wires were at 3 PM next to thw wood brace, so getting to them would've been really tough).

I simply pulled the red and black wires from the inside of the speaker inputs and then removed the top screen, pulling it off and getting some slack in the the two harnesses (they were smart enough to make the wire harness's able to pull out the side of the screen) pulled the metal shoebox forward till it came out of da' woofer hole (that's the big hole at the bottom ) and propped it on a Digi-Key cardboard box. Pics and threads of the garage series of L-300 mods to come. And yes, they sound awesome bypassed! Details to follow! It wasn't easy mind you, figuring it out, but I believe I did and I'm happy with the results.

[Regis]

Thanks Giskard, it's a good thing FoMoCo didn't make it confidential for Autozone to sell me auto parts! Otherwise, I would've never got that fuel pump/radiator/idle bypass valve or computer. And I did it on the driveway too!

[57BELAIRE]

Hi Regis...

On Vintage JBL with the exception of the D123,for not-well-known reasons, positive voltage applied to the BLACK terminal will result in outward cone movement, and also diaphragm movement toward the phase-plug of JBL compression drivers. Check this with a flashlight battery and you'll discover this. As long as all network wires, go to the proper colored terminals, all is fine inside the enclosure...but it's backwards outside at the system input. Really, the only time this might be a problem, is if you're using other mfr's speakers in the same room...say for home theater. If this is the case, your fronts and rears will be out of phase....Please correct me if I'm wrong, and I'll research it further.

It wasn't my purpose to offend you in any way, and If I did, I apologize. I posted the rediaphragm process at the request of Mr. Widget.

I don't recall stating that you need a "clean room" to do this procedure, and you also didn't mention that the drivers were were exchanged and prepped by a Pro. Too much info is omitted in these forums....due to brevity... and can result in bad communication . But your thread was nicely done with the photos ...but some critical steps weren't mentioned.

Rock on up to the Summit,

Edgewound

Am I missing something here? I've always subscribed to the theory that....red/green = pos. and black = neg.

[Zilch]

Am I missing something here? I've always subscribed to the theory that....red/green = pos. and black = neg.

Yes. It's not polarity, rather, phase convention, and JBL, for the most part, uses one opposite what the rest of the industry does, except on SR stuff, which it wires backwards, and selected "anomalous" drivers.

Search the forum. There's reams of info on it here....

[edgewound]

Actually, it is Polarity Convention.

See this link from JBL :

http://www.jblpro.com/pub/technote/tn_v1n12b.pdf

Thanks,
Edgewound

[Figge]

i did this on my 4430:s exacly the way regis did! only diffrence was that i did it alone since the horns are very easy to "pull" on that model, used the floor as working bench, worked out great! i did however not have those 2 pins to "steer it right" so i had to use a tone generator to get it right.