2404H-1 Ring Radiator Diaphragm replacement

[clmrt]

Brief background -

Some weeks ago I acquired a set of 4628B Cabaret. One 2404H-1 was dead, so I procured a replacement dia. D16R2405.

2404 -

http://www.jblpro.com/pages/pub/components/2404.pdf

4628B -

http://www.jblpro.com/pub/obsolete/Cabaret_Series2.pdf

http://www.jblproservice.com/pdf/Cab...ries/4628B.pdf

JBL Pro Parts list

http://www.jblproservice.com/pdf/Tra...rts%20List.pdf

[clmrt]

Using a 9/64 allen, remove the horn from the driver, 4 bolts.

[clmrt]

Is that the pole piece, guys?

Anyway, now's a good time to desolder the two leads on the dead fram. NOTE POLARITY - there's a mark on one lead, a dot. Once done - - -

[clmrt]

Removing the screw at the back of the driver frees the cone thing, which holds the dia centered in the gap. I had to use a utility knife to pry around the perimiter of the old diaphragm to remove it.

[clmrt]

At this point, the battery in my camera died. From here on out, it's all about reinstallation.

I wasn't in a clean room, my tools were rudimentary, and I'm the type who'll slam something together with only reasonable care. I've broken many things in my time...I just plain did this, following no procedure, so don't take this as gospel!

Make sure the gap and coil are free of debris. Drop the coil into the gap and center it as close as possible - Black dot position on the original dia should equal black dot position on the replacement. Rebuild the cone / screw assy lightly. Resolder the tabs.

At this point, I left some play in the voice coil gap, allowed by not tightening the screw on the back. I applied a "good amount" of Hi Pass Filtered pink noise, which I assume would center the coil, and I tightened the screw carefully, so as not to twist the diaphragm.

Check for buzz/ rub. Would be easier with a frequency sweep, but I have none yet.

If satisfied, reassemble the horn to the driver, install, listen...

[clmrt]

Potential issues -

If the coil rubs a tiny bit, it may not be audible? Over time, this will rub thru the wires and cause failure.

Right?

[edgewound]

I love those speakers....4628B. That cone thingy...lol...is the phase plug. The pole piece is directly underneath that, where the screw goes thru to anchor the phase plug. This diaphragm is centered by a relief machined out of the top plate as you discovered by prying the old one out. There's not much you can do to adjust this one if it's not true....no wiggle room. If the coil rubs, you're right, eventually it will die...about the only way I can think of to describe the sound of a rub in this driver would be fingernails on a chalkboard...ohhh...gives me chills just writing that. The phase plug needs to be tight enough so that the center ring doesn't vibrate. As long as the gap is thoroughly clean, and the voice coil is true in the gap, you shouldn't have any problems....wasn't that fun? Good Job!


Edgewound
P.S....yep the only way to test a driver for rubs and buzzes is with a sine wave sweep generator.

[clmrt]

So, I wonder if I should have made an effort to "press fit" the new fram into the machined recess, or will the tightened phase plug do that?

[edgewound]

No...the tightened phase plug has no effect on seating the outer mounting ring...only the inner ring. The horn base might help seat it, but yes...it's best to seat the outer mounting ring, to make sure it doesnt' shift when re-installing the horn assembly.

Good Luck

Edgewound

[Voice]

Using a 9/64 allen, remove the horn from the driver, 4 bolts.

I was searching all over the place, but none of my allen keys fit to 2404 bolts. Have to go and buy a set of inch threaded allen keys.