Restoration of JBL 4350B drivers from The Les Paul Estate auction

[edgewound]

Greetings!
A short while ago, I had the honor and pleasure to restore some damaged drivers that live in a pair of JBL 4350B Studio Monitors that belonged to the late, great Mr. Les Paul. These monitors were purchased from an auction of The Les Paul Estate. The gentleman that bought them was referred to me to get them into proper working condition.

I reconed the two 2202H midbass drivers with my True Reproduction recone kit as factory kits are no longer available, did a resuspension of the (4) 2231H that were previously reconed at the factory with C8R2235, and refreshed the (2) 2440 compression drivers with Radian 1225-16 diaphragms and foam dampening pads. The 2405 slot tweeters just needed a little cleaning under the phase plug. The customer kept the original D16R2440, for posterity, that are still working. Here's a recap of the work...Thanks for your indulgence.

https://www.facebook.com/UplandLoudspeaker/posts/3602289839861430

 

[hjames]

very cool!
Moved to the Lansing Legacy Forum ...

 

[Nyjblbob]

Hello Edgewound,
As an owner of 4350 early Alnico versions, 3 way EN5's with 376's, 4343's and a mint pair of 375's Concec serial #'s,
All have 16 Ohm diaframs. even in your vid the 2440's state 16Ohm. Why then did you replace them with 8 Ohm Radians? I do like them.
and they do make a 16 ohm 4" VC version

 

[edgewound]

Hello Edgewound,
As an owner of 4350 early Alnico versions, 3 way EN5's with 376's, 4343's and a mint pair of 375's Concec serial #'s,
All have 16 Ohm diaframs. even in your vid the 2440's state 16Ohm. Why then did you replace them with 8 Ohm Radians? I do like them.
and they do make a 16 ohm 4" VC version

My mistake, Bob. I corrected the post. They are 16 ohm.

 

[Nyjblbob]

Whew!

 

[GordonW]

My mistake, Bob. I corrected the post. They are 16 ohm.

Since the subject of 8 vs, 16 ohm JBL 2440 and 2441 diaphragms has been brougt up- I have a cautionary tale for others.

The Radian 1245 diaphragms are some of the ONLY aftermarket diaphragms, that actually get the DC resistance RIGHT, for these large-format JBL drivers (2440, 2441, etc). Even though they are nominally 16 ohms (and exhibit between 12 and 16 ohms AC impedance, measured over their useful bandwidth range)- the correct DC resistance is only about 7 to 8.5 ohms!! And, the Radian has a DC resistance of 8.5 ohms +- 10%- certainly in the correct ballpark.

OTOH- I have measured other "generic" aftermarket diaphragms for JBL 2440, 2441, 2445 and such- and the "16 ohm" aftermarket diaphragms tend to measure about 11 to 13 ohms DCR! That's FAR too high for a JBL driver- it will give an effective impedance of somewhere around 20-24 ohms over the driver bandwidth!.

In fact, most "generic" aftermarket "8 ohm" diaphragms actually measure about 8 ohms DCR- which is MUCH more suitable for a 16 ohm JBL driver- it will give much closer to the correct 12-16 ohm impedance across the bandwidth the driver is used in.

So- if you're looking for replacement diaphragms for 2440s, 2441s, 2445s and their ilk- hell, for ANY vintage JBL compression driver- make sure you determine that the DC resistance of the replacement diaphragm matches the original, before plunking down your money!

Regards,
Gordon.