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View Full Version : JBL phenolic diaphragms



Tom Loizeaux
07-29-2003, 05:32 AM
Can anyone talk about how JBL 1.4" phenolics compare to their standard aluminum diaphragms used in drivers like the 2420? What are the characteristics, and pro and cons, of phenolics compared to aluminim...compared to titanium?

Thanks,

Tom

Earl K
07-29-2003, 04:38 PM
Hi Tom

I don't have any small format JBL phenolics. What I have are JBL 2482 - 4" vc, some RCF N481 - 1.75" vc & some RCA - 3" voice coil types . One attribute they share , they are all "softer" sounding than any metal diaphragm I've heard. All nicely damped - my criticism - they're all too damped - as a visual - think "Square-Wave" with slightly "rounded" leading & trailing edges. But that's really a purely subjective thing.

The RCF N481 is interesting in that it has good response up to at least 16K - at the expense of the 800 to 1600 octave. It's a driver that I'd only use above 1500 hz. I just recentered a units' diaphragm to see if it had a problem. It's audible to me that mounted to a 2307 exponential its' running out of torque below 1500 hz - no matter what the manufacturer says . It does have a nice big magnet - though, my 18 year old versions have cheap plastic back-caps .

USAGE:
I wouldn't use any phenolic behind a diffusor such as a 2308 lens . To me, that's adding " a form of diffusion on top of softness". - just my opinion. I also wouldn't ask them to go through the extra "compression-node - throat" built into a typical CD style horn. That's now slightly "compressing softness". Again, just a subjective opinion. Depending on diaphragm size , I'd use them on 60 exponential horns with as big a mouth as your particular circumstances might allow. Here they resolve quite nicely. - my 2 cents :)



regards < Earl K

djk
08-11-2006, 01:28 AM
The RCF N480/81 diaphragm will fit into JBL 1" structures, but is not self-aligning. Seems to have more high end than the 2461/70 JBL phenolics, and at $89 or so are a good deal. They work really well in floor monitors too. Kapton former so they can handle the heat.

Akira
10-25-2009, 10:54 AM
One of my favorite diaphragms is the 2470 1" phenolic.
This driver was everything the 2482 should have been and included a much more extended high end up to 10K. Like the 2482, loads of power, excellent projection and reproducer of vocals with the smoothness lacking of metal diaphragms.
Mated with the 2405 slot and electronic division, IMO the best combo for it's time.

To answer Tom's original question, the phenolic was almost like a super paper speaker operating in the high end. The main qualities was the softness mentioned by Earl K coupled with extreme SPL-- they rarely blew. The original EV eliminators also used phenolics and that small horn pretty well carried that system.

Below: 2470 with dual slots crossed over @ 10KHz--never blew a set of these with years of ROCK touring abuse. 4th order Linkwitz Riley active network was the key to their performance.

Earl K
10-25-2009, 12:31 PM
Wow, the "wayback machine" is alive & well ! This is an old thread .:)

http://www.audioheritage.org/vbulletin/attachment.php?attachmentid=42559&stc=1&d=1256493238

Those are nice . Were they yours ?

I'm somewhat partial to the concept of using "metal UHF over phenolic M-HF" .

>< cheers :)

jerry_rig
10-25-2009, 04:04 PM
I had a pair of 2470s (bought new in 1975) with the 2345 horns, but without UHF assistance. They seemed to be bullet-proof, but sounded very rolled off. To my ear, they lacked detail and depth. I would have "upgraded" them to aluminum, but never got around to it -- assuming that was even possible. Here is a picture of them in custom boxes.

Akira
10-26-2009, 08:43 AM
Wow, the "wayback machine" is alive & well ! This is an old thread .:)

Those are nice . Were they yours ?

I'm somewhat partial to the concept of using "metal UHF over phenolic M-HF" .

>< cheers :)

Yeah, I constructed these HF packs because individually they were a combination of my favorite components. Back in the day I used to use these two packs over a 2482 large lense plate per side for some serious live power. For a smaller club system the single pack was more than enough muscle.

I thought they integrated well above 9KHz (for live apps) but, the magic ingredient as I mentioned was the electronic x/over. Hardly anyone at LH uses the 2405 with an active network, but I have to agree with Greg Timber's -- it makes all the difference. Think of the transition between woofer and horn, which is a much bigger jump than phenolic HF to metal UHF. A high end active system can make or break the transition.

Akira
10-26-2009, 08:47 AM
I had a pair of 2470s (bought new in 1975) with the 2345 horns, but without UHF assistance. They seemed to be bullet-proof, but sounded very rolled off. To my ear, they lacked detail and depth. I would have "upgraded" them to aluminum, but never got around to it -- assuming that was even possible. Here is a picture of them in custom boxes.
As you have found out first hand, it just doesn't sound good with nothing over a phenolic.

mikebake
10-26-2009, 09:20 AM
I also liked 2470, but not so much the 2345 it was on. Mine also had a 2405 on top of it, so the system had extension.

jcrobso
10-27-2009, 08:44 AM
I had a pair of 2470s (bought new in 1975) with the 2345 horns, but without UHF assistance. They seemed to be bullet-proof, but sounded very rolled off. To my ear, they lacked detail and depth. I would have "upgraded" them to aluminum, but never got around to it -- assuming that was even possible. Here is a picture of them in custom boxes.

They are easy to replace, just be careful.