Reconing JBL K140/E140

[StingRay85]

I currently have 4 Ks and 2 Es in decent condition, loaded in big Acoustic cabs. Now I got the chance to buy 3 Ks and 2 Es in need of a recone job for 33€ each. You guys think it's worth the trouble and money? It would be a DIY job, found a great instruction video from simply speakers, and it doesnt look too difficult. I dont mind taking a small gamble on this, it would be great to learn this myself if I want to stick to these drivers.

 

[Stumbo]

I currently have 4 Ks and 2 Es in decent condition, loaded in big Acoustic cabs. Now I got the chance to buy 3 Ks and 2 Es in need of a recone job for 33€ each. You guys think it's worth the trouble and money? It would be a DIY job, found a great instruction video from simply speakers, and it doesnt look too difficult. I dont mind taking a small gamble on this, it would be great to learn this myself if I want to stick to these drivers.

Good price! If that's your tone, I say go for it.

That's the tone I like too.

Do you have cabs for them or would they be backups?

 

[StingRay85]

Thanks for the advice.

I have a 408 loaded with 4 Ks, and a 406w with 2 Es. I also converted a 201 (2x15) to a bass cab, and also have a 402 cab loaded with 2 original Emi's. So they can be either spare or be used in one of the cabs. I really love the sound of alu dome JBLs.

 

[agedhorse]

There are a lot of really crappy aftermarket recone kits on the market. JBL drivers are somewhat difficult to recone properly under good conditions, especially with raw kits (kits are available raw and partially assembled), crappy parts make it impossible to do a good job.

Note that most kits do not have a warranty once installed unless you are a certified installer for the brand.

As somebody with a lot of recone experience, you will find it more of a challenge than you expect. The videos are misleading.

 

[StingRay85]

Can you point out the misleading Parts?

 

[agedhorse]

Naah, you can figure it out on your own, but the very first glaring issue that a pro reconer would cringe at is not using protective gloves. That's about the dumbest thing I have seen this week (though the week is still young).

Hint, the aluminum shavings that get generated by stripping the basket are needle sharp.

 

[StingRay85]

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

 

[agedhorse]

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

Suit yourself. Nevertheless, wear gloves (or not).

 

[StingRay85]

Wearing gloves seems obvious, especially when cutting off the cone and glue residus. All the rest appeared straightforward too. Especially cleaning out the voice coil gap seems the crucial part, and positioning of the new coil on the correct heights. Use the correct adhesives for each joint, and the right amount. It is properly explained so i don't see how it is misleading.

 

[JRA]

you seem to want to do this, per your OP:

It would be a DIY job, found a great instruction video from simply speakers, and it doesnt look too difficult. I dont mind taking a small gamble on this, it would be great to learn this myself if I want to stick to these drivers.

let us know how the re-coning works out --- pics or it didn't happen! good luck!

 

[Wasnex]

Wearing gloves seems obvious, especially when cutting off the cone and glue residus. All the rest appeared straightforward too. Especially cleaning out the voice coil gap seems the crucial part, and positioning of the new coil on the correct heights. Use the correct adhesives for each joint, and the right amount. It is properly explained so i don't see how it is misleading.

If a veteran reconer tells you it's more difficult than it appears, proceed at your own risk.

I have had two speakers reconed in my life...both by experienced professional non-factory reconers. The EVM18B was never right because the voice coil rubbed. I was told to shim the basket. I did this repeatedly and the voice coil would stop rubbing for a few days; then start again. Eventually I bought another driver and sent the bad one to Electro Voice and asked them to either fix it or throw it in the trash. I had a sad story being a veteran, so they took pity on me and reconed the driver for free. It has worked flawless since then.

The second speaker I had reconed was a JBL E120. This speaker was mounted in a cab with a second E120 that has never needed any service. The reconed E120 worked perfectly for several years, but if the driver was bumped the wrong way, the voice coil would stick to the side of the gap. I was able to unstick the voice coil a couple of times because I caught it right away. The last time the voice coil got stuck, the cabinet was being transported over several 1,000 miles. Vibration from the journey caused the coil to become wedged in the gap. The voice coil still had continuity and made sound but I could not break it free without destroying the cone.

The gap tolerances on these speakers are really tight, so the kit has to be perfectly aligned. Rather than reconing the driver a second time, I bought a used driver with the original cone intact.

 

[agedhorse]

If a veteran reconer tells you it's more difficult than it appears, proceed at your own risk.

I have had two speakers reconed in my life...both by experienced professional non-factory reconers. The EVM18B was never right because the voice coil rubbed. I was told to shim the basket. I did this repeatedly and the voice coil would stop rubbing for a few days; then start again. Eventually I bought another driver and sent the bad one to Electro Voice and asked them to either fix it or throw it in the trash. I had a sad story being a veteran, so they took pity on me and reconed the driver for free. It has worked flawless since then.

The second speaker I had reconed was a JBL E120. This speaker was mounted in a cab with a second E120 that has never needed any service. The reconed E120 worked perfectly for several years, but if the driver was bumped the wrong way, the voice coil would stick to the side of the gap. I was able to unstick the voice coil a couple of times because I caught it right away. The last time the voice coil got stuck, the cabinet was being transported over several 1,000 miles. Vibration from the journey caused the coil to become wedged in the gap. The voice coil still had continuity and made sound but I could not break it free without destroying the cone.

The gap tolerances on these speakers are really tight, so the kit has to be perfectly aligned. Rather than reconing the driver a second time, I bought a used driver with the original cone intact.

Yup, the 120 and especially the 110 and LE-8 are really tough as there's not much working clearance in the shallow baskets.

With JBL parts of the K series vintage (the video showed one of the VGT type motors which are easier and the basket/cone deeper) there's much less clearance and if the voice coils are even a few thousandths out of round (very common of aftermarket parts, especially with aluminum ribbon wire) the recone will never meet factory spec. There's a reason why most manufacturers moved away from the shallow basket geometry, especially with tight clearances.

It's a great video, just makes it look way easier than it is in practice on the drivers the OP is looking to recone. It can be done DIY, but I have seen plenty of train wrecks brought into the shop after a DIY attempt. The very worst are where the epoxy soaks through the spider and runs down the bobbin into the gap. Often, these can not be salvaged. Again, this is a bigger problem on the shallow basket geometry as there's not much latitude between the gap and the spider ID.

 

[Stumbo]

I dont mind taking a small gamble on this, it would be great to learn this myself if I want to stick to these drivers.

I think what the pros are saying is that measuring the size of the gamble is more involved because you don't know what you don't know.

Still, since you recognize "the gamble" and are willing to learn on your own dime, nothing stopping you from moving forward.

I also suggest refraining from taking any replies personally. Learn what you can learn and do your thing.

Good luck.

 

[AndyPanda]

The whole point of JBL speaker was that they were very efficient due to the flat wire edge wound voice coil that got a lot of windings into the gap. In those days a 100 watt amp was as much as most people could get their hands on so speaker efficiency was really important.

I worked at a JBL authorized music store and the recone kits from JBL came with the voice coil/spider/cone already assembled (you shimmed the magnet gap with a shim that came in the kit, glued the edge of the spider and cone surround to basket, let the glue set then removed the shim and glued on the dustcap) and the kits cost A LOT and you couldn't buy them unless you were authorized JBL. So other shops would use standard recone parts (round copper wire instead of the edgewound JBL type) and the reconed speaker wouldn't sound any better or any louder (usually worse) than a stamped frame Jensen speaker.

So that's my memory and experience with them --- it was usually cheaper to buy a used JBL speaker in working condition than the price of a real JBL recone kit. (seems like the official JBL recone kit was $100 back in the day)

 

[beans-on-toast]

Do your homework, give reconing the speaker a shot. You’ve had some good advice to help you along. Good or bad result, trying is how you learn.

 

[Bander]

...recone kits from JBL came with the voice coil/spider/cone already assembled (you shimmed the magnet gap with a shim that came in the kit, glued the edge of the spider and cone surround to basket, let the glue set then removed the shim and glued on the dustcap) and the kits cost A LOT and you couldn't buy them unless you were authorized JBL.

Similar kits are available for this series, same process, but from the aftermarket. Cost of the kits near $100 each. Add in the cost of the speaker, and compare with buying a good used driver. Its a better project, if you already owned the speaker, and salvaging it by attempting a re-cone. You still risk the cost of the kit.

 

[SactoBass]

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

Stingray: @agedhorse can back his statements. Valuing the info he shares is a prudent choice.

Of course, it's up to you, and I wish you success with those JBLs. I like those speakers! They remind me of my youth!

 

[agedhorse]

Similar kits are available for this series, same process, but from the aftermarket. Cost of the kits near $100 each. Add in the cost of the speaker, and compare with buying a good used driver. Its a better project, if you already owned the speaker, and salvaging it by attempting a re-cone. You still risk the cost of the kit.

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).

 

[agedhorse]

The whole point of JBL speaker was that they were very efficient due to the flat wire edge wound voice coil that got a lot of windings into the gap. In those days a 100 watt amp was as much as most people could get their hands on so speaker efficiency was really important.

I worked at a JBL authorized music store and the recone kits from JBL came with the voice coil/spider/cone already assembled (you shimmed the magnet gap with a shim that came in the kit, glued the edge of the spider and cone surround to basket, let the glue set then removed the shim and glued on the dustcap) and the kits cost A LOT and you couldn't buy them unless you were authorized JBL. So other shops would use standard recone parts (round copper wire instead of the edgewound JBL type) and the reconed speaker wouldn't sound any better or any louder (usually worse) than a stamped frame Jensen speaker.

So that's my memory and experience with them --- it was usually cheaper to buy a used JBL speaker in working condition than the price of a real JBL recone kit. (seems like the official JBL recone kit was $100 back in the day)

Most of the earlier factory kits were partially assembled because the tolerances were so tight that it took a lot of precision in the field to do it right. There have always been aftermarket parts, most have been pretty dreadful for the earlier model drivers where the tolerances were super-tight. Try reconing an original D-130 (not the F variant), with original raw parts it was VERY difficult, and even with a partially assembled kit it was tough.

 

[Redbrangus]

Unless you just want to learn to re-cone speakers, I wouldn't recommend taking the DIY route. If you're thinking of doing it to save money, I wouldn't take the risk. The labor is a fairly small percentage of the cost of having it done professionally...the 'kit' (of parts) is by far the larger part of it. So if you screw up just one of your first few attempts, you will not have saved yourself anything at all. Making mistakes is a part of the learning process...I'm guessing every seasoned re-coner has made a few mistakes on the path to becoming seasoned. Add that to the fact that a pro guy will warranty his work and it seems like going that route is a no-brainer. The trick then is to find the right guy or the right place. Too involved to address in this thread.

I'm just now realizing that you're probably in the EU, and that your access to real, factory-trained re-coners may be more limited than here in the US. Still, aren't there competent people available to you? If you are in the US, I'd recommend contacting a local PA company to see who they take their re-cones to, if they don't do it in-house. But I have no idea how that would work in Europe, given the relative scarcity of JBL product.

Also, you'll probably find that genuine JBL rebuild kits are prohibitive in cost, if you can even find them, so you're going to be looking for after-market parts. I guess there are some after-market kits that are good enough, if not near-equivalents, but how do you ascertain that? The people who are likely to have valid opinions about which after-market kits are decent enough are going to be the folks who have re-coned a lot drivers.

If you're determined to do the DIY thing, I suggest you only buy one re-cone kit and try rebuilding just one of the E-series speakers. Then you can decide for yourself whether it's worth the effort without having too much invested. From what little I know about it, agedhorse is probably under-selling the difficulty of getting it right on the K-series; your probability of success with those seems unlikely. For my money, given the likelihood of success in rebuilding versus what the value of the rebuilt speaker would be, I wouldn't bother with the K's, but that's just my value judgement.

If you do indeed decide to DIY, you definitely should post an account of how it went, with pics. I'm sure there would be a lot of interest in it 'round these parts. Good luck!

Edit: AndyPanda's post #14 is also spot on.