Phenolic Diaphragms

[Ducatista47]

Merely a curiosity question. Exactly how lo fi are the JBL phenolic compression driver diaphragms? How much improvement did materials that wear out bring? I have thought about this because I am so over the care and feeding of foam surrounds since non self-destructive materials, if designed for the transducer, are performing well in modern speakers.

Since systems using pieces like the 2470 usually allowed for a tweeter, extending the frequency response with metal diaphragms is not considered by me to be an improvement.

[1audiohack]

Hi Clark;

I am not quite sure what you are asking so here’s an attempt.

I think the fidelity of the phenolic drivers is spectacular within their limited passband.

I have replaced the foam surrounds on the 2234’s of my 4435’s with butyl rubber surrounds and consider them a total success.

My 2482’s are in Community Light and Sound BRH90’s, a 13” by 34” radial horn and HF augmentation is required.

Did I get it right?

Barry.

[Ducatista47]

Thanks, Barry. I suspected that the road from phenolic to Be has been about marginal (at best) gains in fidelity that matters to real listeners. The fact that phenolic is completely dismissed out of hand by the audiophile community aroused my suspicion.

The butyl rubber surrounds - how much do they affect the specs of a transducer like the 2245H, 2234 or the 2122/2123? At my advanced age a foam recone would outlast me, but shining a light on this for future maintainers of classic speakers would be helpful IMO.

I think the fidelity of the phenolic drivers is spectacular within their limited passband.

My 2470 question was indeed about fidelity, not bandwidth. My 4345 and 4333 speakers already have bandwidth limiting of the compression drivers with crossovers, so how GOOD phenolic sounds was at the heart of my curiosity. Another consideration is that phenolic does not drift/fatigue out of spec with time. There is something to be said about materials - ferrite and phenolic - that don't change with use. (I am sure I am recklessly interchanging the terms bandwidth and passband, sorry.) I am obviously coming from the perspective that while using pro gear at home is a silly choice for some, the best bicycle is the one you are riding.

[1audiohack]

Hi Clark;

I have pro gear at home and what I have boiled down to I love. A sax or trombone on the afore mentioned horn loaded 2220 - 2482 is something to hear. Also with a large format horn with a 2482 you can get just about all of the female voice except the very high and low ends.

Oh yeah, no harmonic distortion, they don't go high enough to produce any!

Barry.