good old vintage JBL

[bassmonster]

Out of a stroke of luck, my mom's friend's neighbor was getting rid of some old speakers and asked me if I would like them. Turns out they are quite the haul, two JBL L36 and two JBL L166. Best part? Free. They badly need refoaming on the woofers, as the cones are pretty much hanging by a thread of surround material, but the L166s still have the unique 'egg-crate' style grille in good condition. Are these worth the effort to refoam four drivers? I say, they make my current bookshelf speakers (6.5") look like pea shooters. I bet when I finish refoaming them they will sound absolutely glorious alongside the TT...

What say ye? Any vintage speaker restoration projects you guys have done? I plan on restoring the walnut finish, too. Pics to come.

[Grant Bunter]

First up,
Sit those cabs on their backs!
That will kinda prevent any more movement for the time being.

We have them here, so I'm sure if you can't get genuine parts (which no doubt cost more), some company locally will have new for old foams. Just make sure the dimensions are pretty precise. I'm sure you could get the info from JBL if there is any doubt.

You only have to rub the old foam with your fingertip and a cotton cloth and it will fall off the frame and the cone. You might like to check impedance of the VC before you go anywhere at all to see if it's in spec.

You'll have to (carefully) cut out the dustcap to put shims in to re centre the voice coil (and if the company you get the foams from doesn't supply the shims, go elsewhere) before you go ahead and refoam. Let it all set for a day, before you pull the shims out and reinstall the dust caps (unless the replacement dust caps are the correct size, but this isn't always the case).

Otherwise, good on you

Hope this helps...

[bassmonster]

Wow, thanks, I will be sure to lay them on their backs when I get home. I can get some recone kits off Ebay with the shims and replacement dust caps so I will do that.

[Grant Bunter]

If the VC is ok, you don't need a full recone, just replace the surround...

[bassmonster]

I haven't touched them because I don't want to damage the driver, but I think they're OK. Otherwise they are in great condition, still have the original box and documentation. The midrange and tweeters are fine, no rips or surround decay.

[Grant Bunter]

Cool, less work the better.

If the insulation on the VC is good, you should be able to check continuity and resistance straight of the connector tabs.
If the insulation is a tad worn from rubbing on the pole piece, you may have to get the shims in first to check it.

Did you mean these (or something similar)?
http://www.ebay.com.au/itm/JBL-L36-Spea ... 0434680591

http://www.ebay.com.au/itm/JBL-L166-Spe ... 0705787423

[bassmonster]

I don't think they've been played for many years. They were in an attic and that's how the foam rotted, so I don't think they have been played while the foam has been rotted. I tested them and they make noise, so I won't touch them until I finish refoaming them. I found my camera and will upload pics later.

[bassmonster]

Yep, those in the links are like the refoam kits I'll be ordering when I have the time to refoam them (probably this summer).

I put a few watts through the L36's early today, as the surrounds on those are still intact enough to play softly without rubbing the voice coil, plus I just had to hear them.

They are officially the most beautiful mains speaker cabinets I have ever heard. The sound just kind of envelops you and doesn't tire your ears out. I sat on the floor with my mouth just hanging open for awhile and listened to them for a straight hour alongside the TT. They are so detailed you can hear the individual plucks of a pick against a guitar string. I heard things I'd never heard before. MP3s sounded like compressed, distorted garbage with the clarity; the only way to listen to these speakers is with real high quality stuff. The L36s make my other bookshelf speakers sound like they are being played through a pillow, and the L36s sing bright and clear.

Wow, I love vintage speaker cabinets. They even smell good, nice and musty like the inside of an old ragtop Volkswagen. I should have been born in the 60s or 70s. I can't wait to refoam and hear the L166's. They use the special aluminum-deposition dome tweeters that are SUPER rare nowadays, so I better be careful with those.

Onto the pics:



Size comparison to the tiny MTX Monitor 5i, and yep, the L166's need a refoam, badly:

[Rickisan]

bassmonster,

I have refoamed (replaced the surrounds) of 5 or 6 pairs of vintage speakers... Advent, Genesis, B&W, Pioneer. I have never used shims for the magnet/pole piece. The spider always self centers the cone... in my experience. Most recently, last month, I did a pair of Advent 3's... there were no shims in the kit.

To test the spatial functionality of the cone/coil magnet assembly... center the cone equidistant from the metal basket around the outer edge with one hand. Now, with the other hand, push down gently on the center of the speaker, near the dust cap. It's ok the speaker should move easily for a 1/4" or so up and down... If you don't hear any scraping during this test you don't need shims.

Cutting in to the dust cap to add shims is totally unnecessary and an added risk and strain on the cone in my humble opinion. YMMV.

I would love to hear from anyone who has used shims and why shims were warranted.

Respectfully, Rickisan

[byacey]

JBL's are generally pretty forgiving because they have a relatively wide gap.

EV's and others can be very tight, and if everything isn't centered dead on, they rub. You shouldn't rely on just the spider to hold the coil centered as the woven cloth can fatigue over time allowing the coil to sit canted to one side with respect to the gap. Once shimmed, it's important to drop the surround into place after applying the glue, and let it fall and sit where it may. Don't try and push and pull on the surround in an attempt to make it appear more - centered with the basket rim edge. Doing so puts uneven tension on the cone, and can also cause rubbing.

[Grant Bunter]

bassmonster,

I have refoamed (replaced the surrounds) of 5 or 6 pairs of vintage speakers... Advent, Genesis, B&W, Pioneer. I have never used shims for the magnet/pole piece. The spider always self centers the cone... in my experience. Most recently, last month, I did a pair of Advent 3's... there were no shims in the kit.

To test the spatial functionality of the cone/coil magnet assembly... center the cone equidistant from the metal basket around the outer edge with one hand. Now, with the other hand, push down gently on the center of the speaker, near the dust cap. It's ok the speaker should move easily for a 1/4" or so up and down... If you don't hear any scraping during this test you don't need shims.

Cutting in to the dust cap to add shims is totally unnecessary and an added risk and strain on the cone in my humble opinion. YMMV.

I would love to hear from anyone who has used shims and why shims were warranted.

Respectfully, Rickisan

I've used shims, they were supplied with the kit.
The method described with the surrounds when they arrived to me said to remove the dust cap and place the shims to ensure the VC is centred. I guess the spider, with it's usual concertina form, may allow the VC to be off centre marginally, and the added support of the surround after centring prevents deviation.
Each to their own, if one doesn't wish to use the shims, so be it...

[Bill Fitzmaurice]

The method described with the surrounds when they arrived to me said to remove the dust cap and place the shims to ensure the VC is centred.

And there's the rub, removing the cap. I would do all of the prepping except for removing the cap and then feed the driver with a low frequency sine wave sufficient to get a fair amount of excursion. if you get coil rub pull the cap and shim the coil. If you don't I'd skip that step.

[byacey]

If you do have to remove the cap, use a razor sharp exacto knife, and hold the blade parallel with the plane of the cone. Carefully cut just through the dustcap as close to the glue line as possible. Be careful around the tinsel lead area, as to not cut through the leads that are often buried in glue near the cap glue joint.
If done carefully, you can re-use the dust cap.

As Bill suggested, it's wise to leave the cap in place until the new surround is ready for gluing, as it will prevent fallout while prepping the surround from getting in the gap.

If the speaker is a dual spider type, the coil will stay centered without any shimming.

[Grant Bunter]

If you do have to remove the cap, use a razor sharp exacto knife, and hold the blade parallel with the plane of the cone.
If done carefully, you can re-use the dust cap.

As Bill suggested, it's wise to leave the cap in place until the new surround is ready for gluing, as it will prevent fallout while prepping the surround from getting in the gap.

^ And this is what I did, but used a stanley knife blade freehand.
As to if I should have done it (ie removed the dustcaps and put shims in), well, it was in the instructions/"plans" and we all try to follow the plans here

[bassmonster]

Thanks folks. I've read the dust caps are very difficult to remove due to the glue JBL used, and also that the VC tolerances are pretty tight. I'll try to do without the shims at first, but I will use them if it's too tight for comfort.