Reconing JBL K140/E140

[2tonic]

There is a reason companies like McCauley and Peavey invested so much capital to produce transducers with field replaceable baskets.
Pre-assembled units that could be changed out with no muss, no fuss.
Remove the torn/blown cone, basket and all, clean the gap, then position new basket and bolt it down.
You had to exercise a little more caution than a monkey, but you ended up with the equivalent of a factory fresh speaker.

And you could do it in the twenty minutes before show time, because that's always when you discover a bad driver!

 

[agedhorse]

There is a reason companies like McCauley and Peavey invested so much capital to produce transducers with field replaceable baskets.
Pre-assembled units that could be changed out with no muss, no fuss.
Remove the torn/blown cone, basket and all, clean the gap, then position new basket and bolt it down.
You had to exercise a little more caution than a monkey, but you ended up with the equivalent of a factory fresh speaker.

And you could do it in the twenty minutes before show time, because that's always when you discover a bad driver!

Correct, and they compromised on the gap width tightness because the last dB of sensitivity wasn't as important as a reliable initial build and repair.

 

[DJ Bebop]

Ok, so you make big statements that you can't back. In this case I cannot give much value to this opinion

DUDE!

 

[SAlcott]

Ok, so you make big statements that you can't back. In this case I cannot give much value to this opinion

The person at whom this comment is directed has forgotten more than most of us will ever know about this subject. Buy the kits, do the recones, and be sure to let us know how it turns out.

 

[Chad Michael]

Ended up with a vintage set of Boston Acoustics A40 series II speakers (trade with a friend).

Woofer surrounds were shot. I decided to do a 're - edge' job on my own, seemed simple enough. I lucked out in some ways, the kit I got was great in terms of quality and instructions. However, let me tell you it was tedious, and a labor of love. Trying to remove the bad yet leave the good un-harmed...

Those A40's are in my garage, sound fantastic, and gave me a story to tell. I'd be proud to have anyone hear them, but I don't know if I'd do it again. Best of luck - give it a go, but do your homework first.

 

[Bander]

Ended up with a vintage set of Boston Acoustics A40 series II speakers (trade with a friend).

Woofer surrounds were shot. I decided to do a 're - edge' job on my own, seemed simple enough. I lucked out in some ways, the kit I got was great in terms of quality and instructions. However, let me tell you it was tedious, and a labor of love. Trying to remove the bad yet leave the good un-harmed...

Those A40's are in my garage, sound fantastic, and gave me a story to tell. I'd be proud to have anyone hear them, but I don't know if I'd do it again. Best of luck - give it a go, but do your homework first.

I've done surrounds several times. Sounds like a full recone is an order of magnitude more risky for these JBL's.

They look similar but the tolerances are not, specifically the roundness. On the tighter gap motors this is a very real issue. This is why JBL discontinued the very tight gaps as power amps got larger. When the VC heated, everything had to be perfectly concentric to avoid a skewing of the moving parts on axis. The original motors had a gap increase of about 0.005" early on (F suffix and K series) and became even wider as the winding gauge and displacement increased. All of these factors must be considered when reconing. It's also some of the information and tools that you learn when you go through the JBL reconing school and certification process (I did this I think in 1978 or 1979).

I guess I'm glad I didn't attempt it then, I'd been pretty disappointed with a rubbing vc after spending $100, and a Saturday in vain. My frugality paid off for once.

 

[StingRay85]

DUDE!

Note that I said this before he edited his post. It turns out the topic got very constructive, thanks for that

 

[StingRay85]

Passed on the deal. It makes more sense to only look for drivers in good condition. Often they go for less than a recone kit.

 

[BogeyBass]

Gotta give the video guy credit though, makes it look pretty easy.

And whenever I'm bored watching geeky
Recone videos. Makes me happy watching speakers get reborn.

You could always just practice on a pro series Eminence, to get used to the cleaning and glueing process

 

[byacey]

The glue that JBL used in those days was a Bostik product; very difficult to remove and clean up a basket. Much scraping had to be done to remove most of the glue. The new surround and spider glues let go so easy in comparison that I'm surprised they don't let go when the speaker is being used.

 

[agedhorse]

The glue that JBL used in those days was a Bostik product; very difficult to remove and clean up a basket. Much scraping had to be done to remove most of the glue. The new surround and spider glues let go so easy in comparison that I'm surprised they don't let go when the speaker is being used.

Hence my cringing when not using protective gloves.

 

[Munjibunga]

Ok, so you make big statements that you can't back. In this case I cannot give much value to this opinion

Oops.

 

[BogeyBass]

So the K and E series have the wider gap clearance then?

I'll take as many K series I can get regardless cause I know how they sound

 

[agedhorse]

K series has a slightly wider gap than the original D series without the F suffix and the 2220. I believe the E series is wider because the VC thickness increased, but would have to check my legacy docs.

 

[Omega Monkey]

Yeah, the thing to do with these would be to buy them and then send them to a professional to recone. But it sounds like you already have a zillion of these anyway, so if you don't have a specific function for these it makes more sense to leave them for someone else.

 

[StingRay85]

Yesterday scored two K140s and two D140F, for less than any recone set you can buy...

 

[Blue]

Buying a used speaker ... what are the telltale signs it's been reconed, opposite just taking the sellers word ...

 

[StingRay85]

Cone codes are your best friend

 

[Seagrass]

I have two speakers D and K
Can you help me determine from these pictures whether they are original or not?

The first two photos are D140f
The rest are K140

Thank you!

 

[agedhorse]

Buying a used speaker ... what are the telltale signs it's been reconed, opposite just taking the sellers word ...

Marks that happen during a recone (see below), non-JBL part numbers, non-JBL adhsives, etc.

I have two speakers D and K
Can you help me determine from these pictures whether they are original or not?

The first two photos are D140f
The rest are K140

Thank you!

It's very hard to say, I usually look for telltale signs of recone work, including blade marks on the basket at the underside of the surround.