Sloped front JBL?

[jbl-ahhh]

Does anyone know of a JBL speaker other than the L3 (see photo) that has a flat front on the bottom half and drivers on a slanted front on the top half? The owner of the ballet studio where my daughter dances uses a pair of 13 or so year old JBLs shaped like that but isn't sure what model they are. She says one of them "has slowly started making a bad sound" so I told her I would try to fix them.

Maybe just a shot surround causing the voice coil to rub. Hopefully she hasn't been playing them since the noise started. What damage is common if a driver is played too much with a decayed surround? Does the voice coil crack or the spider get torn?

[BMWCCA]

Could be any of the entire L-series from L1 to L7. You might want to ask how many drivers are in each cabinet, or just have her look on the back "where the wires connect" and read the model number. All of those L-series use rubber surrounds so they're likely not deteriorated but they could have come unglued and that could cause a "flapping" sound.

So, how do you know it's not an L3?? What information did you forget to share?

[jbl-ahhh]

My original post wasn't very clear. Sorry 'bout that. It definitely could be an L3, but I won't know for sure until Tuesday when I pick it up because she doesn't know much about it and can't get it down by herself from its high perch. My daughter says the bottom part of the cabinet is not slanted and has no drivers, so it's not an L1 or L5 or L7. If JBL made other slanted front speakers around the mid 1990s, then it might not be an L3.

I offered to try to fix it and was hoping to get information on any other possible models so I'll be a step ahead come Tuesday. In case it is an L3, knowing about the rubber surrounds helps. Thanks. If the rubber surround is coming unglued from the basket, that would be an easy fix.

[BMWCCA]

If the rubber surround is coming unglued from the basket, that would be an easy fix.

You might want to do a search here for "butyl" or "rubber" with "surround" and see what the collective wisdom over the years says about it. I hesitated to buy any of the L-models after reading about separation here. That being said, many have offered different solutions to the type of glue to best affect a repair. Myself, I've never had any of my four pair come apart. Personally I'd still try Aleene's Tacky Glue first. Available at WalMart and Michael's, and many others.

Was there more to the description than just the "bad sound"?

Good luck. And remember, we love pictures!

[jbl-ahhh]

Yep, Aleene's glue worked great reattaching portions of the rubber surrounds on my vintage Infinity woofers. (Can I use the "I" word here? ).

No additional problem description from the owner. I'll post Tuesday or Wednesday about what I find and include pics. I'm hoping for the best. After all, I don't want my daughter dancing to less that fully functioning JBLs!

[BMWCCA]

Yep, Aleene's glue worked great reattaching portions of the rubber surrounds on my vintage Infinity woofers. (Can I use the "I" word here? ).

Actually Infinity is part of the Harman family these days so you're okay there. I used Rick Cobb's glue on a set of surrounds for some Infinity RS-4001 speakers with the Injection-Molded-Graphite cones and it worked great...just like Aleene's.

[Rudy Kleimann]

To clean the backside of the cone, make a support shim with a piece of styrofoam (or anything similar) about 1/2" thick. Cut a circle just small enough to clear the frame, but large enough to overhang the edge of the cone. A slightly snug fit in the frame is best.

Then, place the driver face-down and lightly push it down until the styrofoam contacts the cone and the frame is contacting the work surface. Assuming the 1/2" thickness of the styrofoam disc is appropriate, the cone will rest against the foam, perhaps being pushed in slightly from its normal resting position, but not so deep as to bottom out the voice coil in the magnet or stretch the spider to a ridiculous degree. Now, scrub away on the rear edge cone with a toothbrush to remove the old surround without fear of deforming the cone or bending the voice coil.

Follow up with a cleaning solvent like MEK (a favorite of many LHS guys) to remove the last of the old surround (test styro or other material supporting the cone with the MEK and remove it first if the MEK attacks it) and dissolve the old glue or at least level it out. Use it sparingly to avoid saturating the paper cone and wear gloves to keep the MEK out of your system, lest you end up with a nervous tick, a third eye in your forehead, or God only knows what else it might do to you. Work in a well-ventilated area.

Remove the dust cap (MEK to soften the glue here too, provided it doesn't attack the dustcap, or mark the cone and cap then exacto-knife the cap right along the glue line) and shim the voice coil around the pole piece. Narrow strips of thin plastic slid in side-by-side, just thick enough to spring-load the coil against the pole piece without necessarily completely filling the gap works very well. Get it to a near-interference fit. Whatever you use, make sure it won't leave any behind in the magnet. Leave it shimmed until after the surround is set and the glue is dry, then reglue the dust cap.. Some guys pull the shims and shoot low-power LF tones to the woofer while the glue is a little soft to get it moving and check for voice coil rub, the ide being you can play with the surround position on the frame or the cone itself before the glue sets. I don't do this particular trick myself... your mileage may vary.

[jbl-ahhh]

Hey, that method for removing the old surround definitely sounds worth a try, but I already got mine off. With the driver magnet side up, I managed to use a small screwdriver to pry one spot of the old surround away from the underside of the cone enough to get a finger in between surround and cone and then gently, slowly ease the surround off of the cone all the way around, a little at a time. I used heat from a hair dryer to loosen the glue but I'm not sure it did any good because in one of the pics you can see that a very thin layer of cone got peeled off with the surround. Not ideal, but the cone seems fine.

Once the surround was free from the cone, I flipped the driver over to get the surround off of the basket. I just used a small screwdriver underneath the surround to scrape it off. The surround lip is only 1/8" wide, so it comes off easily.

Next, by pinching the surround between my thumb and index finger and pulling very lightly and slowly, the glue bead along the outer edge of the cone came free - see pics. I used a finger pressing on the cone to counteract the pulling force. Came off clean as a whistle!

The search for exact fit replacement surrounds goes on. Looks like I'll have to go with "close" and then trim them to fit. That narrow 1/8" outer lip must be quite unusual.

[Rudy Kleimann]

WOW! That's the narrowest lip on any surround I've ever seen! That's going to be a tricky one. How much are the recone kits? Most JBL FASC charge $25-35 labor to install. Sometimes, however, new woofers are the only factory option, which is sometimes pretty high $$.

If your only viable option is made-to-fit surrounds, find or make a jig to cut the rim of the surround to fit. Raid the kitchen pantry for things like pots and pans or covers, tupperware, margarine tubs, old metal coffee cans, anything that will snugly fit the recess in the frame and fit over the roll of the surround. maybe even the next smaller woofer frame will be right, if you happen to have one handy. If nothing else, get some sheet metal and roll it into the correct diameter tube. Just be sure the surround is pulled out evenly all around, with the right amount of surround flange left inside the edge. Then get after it with a fresh exacto knife (easiest to use for the best job) or a razor blade on a cutting board. You can use the same to

On the glue, less is more, as long as it's evenly applied. You sure don't want overflow creeping up into the rolled area of the surround.

Just a few ideas that came to mind, FWIW.

[mikebake]

My idea is to get something more substantial for a dance studio; like a 15 and a horn.

[Rudy Kleimann]

Like JBL MR 825's?

I have 1pr in fairly good and 1pr in very good cosmetic condition (all drivers are original in excellent condition) that would do a good job and prove handy for the studio. Lightly used, mostly for Karaoke. I don't use them much anymore after moving up to 2226/2447 -equipped cabs and would sell them at a fair price.

Offers?