Please help ID these Diaphragms from JBL CD

[Champster]

I just bought 4 2425 1" Compression Drivers and I definitely need to change at least one of the diaphragms and I want them all to be the same. These 3 pictured all work fine, but there aren't any markings on them to tell me who made them. Can you help me identify them as JBL or aftermarket?

Thanks,
Paul
6202862029620306203162032

[JuniorJBL]

They do appear to be 2425/26 motors. Maybe a pic of the front and the back cap would help.

[Champster]

Thank you JuniorJBL but they are definitely 2425h motors. I need the brand of the diaphragms.
Paul

[grumpy]

They appear to be JBL D8R2425 diaphragms
(why 8ohms? looks like a green blob on + terminal, vs red)
(why Ti? the reflection doesn't look like Al, and few people spend
the money to put Al diaphragms in a 2425/6 motor, as most are in
PA or studio gear that gets beat up, and Ti takes a beating better)

http://www.audioheritage.org/vbulletin/showthread.php?30435-how-can-you-tell-real-JBL-diaphragms-from-aftermarket

[Champster]

They appear to be JBL D8R2425 diaphragms
(why 8ohms? looks like a green blob on + terminal, vs red)
(why Ti? the reflection doesn't look like Al, and few people spend
the money to put Al diaphragms in a 2425/6 motor, as most are in
PA or studio gear that gets beat up, and Ti takes a beating better)

http://www.audioheritage.org/vbulletin/showthread.php?30435-how-can-you-tell-real-JBL-diaphragms-from-aftermarket


Thank Grumpy. I'm sorry for not including the color dot. I meant to but forgot. It is green which I believe is 8ohm, right? These definitely have a gun metal gray color as opposed to a bright shinny silver color. Looks more Ti than Al to me. For home stereo are you saying the general consensus is that Al is smoother and better sounding?
Thanks,
Paul

[Mike Caldwell]

I going to say the diaphragms are authentic JBL. As already mentioned the green ink dot on the terminal to indicate the positive terminal on an 8 ohm diaphragm. The knock off diaphragms I've seen have had a red dot sticker next to positive terminal. The diamond surround impression is nice and sharp and the outer edge has shows a coating of glue. On some knock offs the diamond surround pattern is smaller and or does not have the clean crisp edges. They look just like the real thing I just compared to your pictures.

[Champster]

Thanks Mike. I see folks carrying the Ti driver but can't find the Al one Grumpy referred to? Is about $140-$175 about the going rate for a JBL diaphragm these days?

[grumpy]

...For home stereo are you saying the general consensus is that Al is smoother and better sounding?

Consensus? LOL. This is a public forum with opinions all over the place.
But sure, I think so. They also have a limited lifetime, more so when abused,
and are pretty expensive ... ~$340/ea, so it makes Ti or Radians not look so "bad"...
and one can always hope for TrueXtent 1.75" Be units to pop out of the years-old
oven. Actually, any of those alternatives seem to be consistently better than the
typical ebay aftermarket "equivalents", and there are proponents for each.

Or go TAD. I haven't (went with TrueXtent large format), but there's pretty consistent
praise of TAD vs. stock drivers in JBL 43xx monitors (perhaps with some crossover redesign).

JBL part would be D16R2421 or D8R2421 for the diamond pattern Al part. I don't know
if you can even buy the tangential surround units any more.

[Mike Caldwell]

What makes you think you need to change on of them. Does it sound different in some way? Maybe the gap needs cleaned and the diaphragm re seated. Do you have a tone generator, putting some 400hz to 500hz tone on the diaphragm will make it easy to tell if it's centered and evenly tighten down. Even though they do self center theres still a little play to work with. A diaphragm or any speaker for that matter that's has the voice coil heated up to the point of almost burning out can still work but may be rubbing and or have a few shorted windings both causing them to sound at least different to down right just plain bad.

[Champster]

What makes you think you need to change on of them. Does it sound different in some way? Maybe the gap needs cleaned and the diaphragm re seated. Do you have a tone generator, putting dome 400hz to 500hz tone on the diaphragm will make it easy to tell if it's centered and evenly tighten down. Even though they do self center theres still a little play to work with. A diaphragm or any speaker for that matter that's has the voice coil heated up to the point of almost burning out can still work but may be rubbing and or have a few shorted windings both causing them to sound at least different to down right just plain bad.



I bought this "pristine" unit about 6 months ago on eBay. It looked so good, I never even checked it until a week ago....
I was able to clean up the motor with lots of TLC but I'm afraid this diaphragm is done...
6206562066

The other 3 pictured above came from a movie theater in Boston that was being torn down, so I'm assuming they've had some hard use over the years. The 3 pictured all work and sound fine, but I thought it would make sense to start fresh with new diaphragms for all 4 CD's.

Make sense?

[grumpy]

It would probably be "safest", but perhaps unnecessary...
Mike's advice is sound (as usual) :)

[Mike Caldwell]

That's was one toasted diaphragm, cleaning the motor up that it came out would have taken some serious measures.

As for the drivers you have now I would pull them apart, clean the gaps, look at voice coils for signs of excess heat or physical damage, tone sweep and center and I think you would be set.
You may want to check the foam in the drivers back caps. On some of the wires it looks like there is some evidence foam residue stuck to the wires.
New back cap replacement foam is available from JBL precut with peel and stick tape.

[Champster]

That is all good advice Mike. Thank you! I will be putting in all new Radian diaphragms after cleaning them up like you suggested. Good eye on the foam. It was completely destroyed on all of the 2425's. I have found the folks at JBL in Northridge to be super helpful with spare parts to bring them back to new. They will be as good as new and all sounding very similar with all new diaphragms.

Thanks
Paul