LE15 Surround Question / compression Driver question

Hi, trying to get 2 questions answered in one thread.

If one has an good LE15 (A or B too) with a stiff Lans-A-Loy surround, should it be resurrounded with foam as a workable repair (not too keen on the brake fluid idea)?

If a recone instead is recommended, what kind of surround does the recone kit come with?

OK, 3 questions :bouncy: . With JBL compression drivers, many like the 242x and 244x series have a open cell foam pad in the back cover/chamber. How important is that for the sound and what do you replace it with when it becomes brittle and crumbly after all these years? I couldn't find any exploded diagram about the 2420 for example that listed a part number I could order from JBL Pro.

Thanks in advance for the replies and information.

Regards,

Bart

Quote:

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Originally Posted by mech986

If one has an good LE15 (A or B too) with a stiff Lans-A-Loy surround, should it be resurrounded with foam as a workable repair (not too keen on the brake fluid idea)?

If a recone instead is recommended, what kind of surround does the recone kit come with?

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A). LE15B has a cloth surround.
B). There are Foam surrounds from OCS and others that are regularly on eBay or that may be purchased from various suppliers like Rick Cobb that are either exactly like the new foam surrounds that come with the full recone kit or are close enough. If you buy from a reputable supplier you will get the correct surround... do some searches on this site.

C). A complete recone is the best solution as the woofer's spider tends to wear as well, but the JBL recones are not inexpensive. They are fully assembled from the factory with the spider, voicecoil, and surround already glued to the cone and when installed by a factory authorized service center come with a warranty and will guarantee you have an essentially new woofer... you may want to recharge the magnet to be sure. (Do some searches for this as well.

Quote:

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Originally Posted by mech986

OK, 3 questions :bouncy:. With JBL compression drivers, many like the 242x and 244x series have a open cell foam pad in the back cover/chamber. How important is that for the sound and what do you replace it with when it becomes brittle and crumbly after all these years? I couldn't find any exploded diagram about the 2420 for example that listed a part number I could order from JBL Pro.

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There is no longer a replacement foam pad for the 242X drivers but you can easily cut down the 2440/2441 foam pad. It is part #60398 and costs $2.28 ea.

...and yes it is necessary.


Widget

Hi Widget,

Thanks for the reply. Some request for clarification and branching the questions a little bit:

If the driver has Lans-A-Loy, then the accepted repair is new foam or better still, a complete recone that has a newer JBL foam surround. In the eyes of the user, this restores a poorly functioning unit to use, but, in your opinion, subjective or objective, what does it do to its resale value, either as an individual driver, or as part of a system (like the C50 or C60)?

(Sorry for posting that question here as that likely is a Marketplace question but since the two issues are linked, I thought I'd continue here, Moderator may feel free to move if needed).

Thanks for the info on the 244x pad that can be used. Is there anything special about the foam, do you think other foams or shapes could make much difference? (yes maybe more of a DIY question, sorry :blink: ).

Also, it seems a good cleaning of the mating surfaces would always be indicated if the compression driver is opened. Does the rear cover require any type of special sealing/sealant at the terminals or mating surfaces, or the diaphragm mounting ring for that matter?

I always wondered if the compression driver was designed as a completely closed system, sealed up like a minature speaker cabinet with a sealed or lossy back chamber, diaphragm mounted on the top plate like a baffle, playing into a particular horn structure. With the kind of sound pressures that can be created on either side of the diaphragm, seems like any small or moderate leaks could affect the drivers' "tuning" as it were".

Or is that a bit too anal thinking. I was looking at that sort of in relation to the discussions of cabinet port tuning between two choices that were only a few hertz apart. If the bass tunings are critical and audible, wouldn't the assembly and sealing of a compression driver have effect on the critical midrange?

Thanks for the replies.

Regards,

Bart

If the Lans-a-loy is clean and crack free and the cone is really nice looking it will likely be worth more left alone. It will sound best reconed, but your investment will likely exceed it's replacement cost. Since Lans-a-loy has been out of production since ~'74 all properly functioning LE15(A)s are either treated with brake fluid or have a gray foam surround.

As for the damping pad. There are so many foams... I'd expect a different foam could be used and you'd have equivalent performance... but for a little over $2... why would you substitute?

I wouldn't worry about opening the rear chamber... be careful of the strong magnetic field as it tends to pull screws and screwdrivers into the dome. I would recommend not messing with the diaphragm unless you know what you are doing. Many JBL compression drivers that I have opened have become stuck due to oxidation. A slight rap on the side after screw removal may be required.


Widget

I bought a beautiful original blue-driver S7 pair a few years ago. The surrounds were like rocks, but responded to brake fluid like you would not believe. Nice and compliant now.

I agree with JRL. I acquired a pair of JBL Apollos (circa 1965) whose LE15 surrounds were hard as a rock. It was no surprise, then, that they didn't have much, if any bass to speak of.
I was hesitant to try the brake fluid which I read about here, but figured, "What the hell, I'll give it a shot."
It was worth it, because these things perform wonderfully now....and it didn't alter the appearance at all. I'm impressed. :D