435BE vs 2435HPL

[norealtalent]

Finally got my little grubbies on a REAL 435BE . Heres my observations between the two;
BOTH have ferro fluid.
Both appear as identical drivers in EVERY way.
Diaphragms do interchange and appear identical in every regard excepting that: the 435BE has a black coating on the front of the diaphragm and is bare on the back:
the 2435HPL is a bare diaphragm on both sides.

[speakerdave]

A dusting of aquaplas I 'spects. Don said in one of his posts that they had considered this but indicated they had abandoned it, as I recall.

David

[Zilch]

I recall the 435Be I examined did not have ferrofluid.

However, in frequency response tests at least, any performance differences were indiscernable:

http://audioheritage.org/vbulletin/s...page=5&p=63329

[stevem]

I'm really glad to hear all this 'cause I'm expecting my 2435H drivers tomorrow!

[Guido]

However, in frequency response tests at least, any performance differences were indiscernable:

I think the aquaplas coating is highly audible and should result in a smoother sound.
Anyway I do only guess here as I don't have 2435 and 435 drivers.

[Zilch]

Keep to the path, Guido:

2431H has better extension....

[Mr. Widget]

I think the aquaplas coating is highly audible and should result in a smoother sound.
Anyway I do only guess here as I don't have 2435 and 435 drivers.

I would tend to agree with you. While we had examples of both drivers here and their measured frequency response plots were very similar, that doesn't mean that while listening to music they would sound exactly the same. I really don't think JBL is spraying the aquaplas for their ego's. The same goes for the larger back cap. While our measurements didn't show a significant difference at lower frequencies, that doesn't mean that they will subjectively perform the same way when used down to 800Hz. Again, I think the back cap is there for a reason. The heat sink ribs are there for a reason too... to look cool and sell more speakers.

Mr. Talent,

As for both drivers using ferofluids? I was under the impression that the 435Be is not supposed to have ferrofluids in the gap. I assume you bought the 435Bes on the used market? Perhaps the fluid was added?

Have you done any listening comparisons? What horns are you/will you be using with them?

Widget

[Zilch]

If the 435Be does not have ferrofluid, the larger back cap with fins would make sense for heat dissipation.

In the same vein, 2435 (and the rest of them 243x) has Silpad on the face for thermal conductivity to metal horns. Where plastic horns are used, JBL places a heat sink plate between the driver and the horn in some products.

435Be would have the same issues on the S9800 polymer horn. That's not an aluminum block it bolts to on that, is it? No fins there, in any case....

[Mr. Widget]

If the 435Be does not have ferrofluid, the larger back cap with fins would make sense for heat dissipation.

Let's see... with a basic sensitivity of 108dB/watt and a typical loud domestic listening level of 98dB ... that would require 100 milliwatts... how much heat?


Widget

[Zilch]

... that would require 100 milliwatts... how much heat?


Widget

That depends on the total thermal resistance. Heat sinks don't make much sense for home use, I agree. JBL does it, though, maybe to minimize power compression in high end stuff....

[Don't MAKE me find where I saw that now.... ]

[edgewound]

Let's not forget that when a compression driver is crossed-over lower, say 800hz, there will be some sacrifice to the high end. That diaphragm can only do so much till it says "no more". The aquaplas coating does a fine job of smoothing out the distortion of the titanium....some would argue that it doesn't "cut through" as well with the damping....when what's really going on is the distortion that's "cutting through" is cut down, and your ear's are thankful for that. Ferrofluid has some of the same effect at dampening the moving mass, albeit at the slight expense of sensitivity...but can help power compression too. What can raise some eyebrows though, is why is there a need to dampen a beryllium diaphragm? The JBL casting technique must not quite reach the results of the TAD vapor deposition process of manufacture. The first resonance of the TAD is 25KHZ!

[Zilch]

The aquaplas coating does a fine job of smoothing out the distortion of the titanium....some would argue that it doesn't "cut through" as well with the damping....when what's really going on is the distortion that's "cutting through" is cut down, and your ear's are thankful for that.

I've had that concern when boosting HF. I can't actually hear that stuff approaching 20 kHz, though I see it on the RTA, and wonder if all I'm doing is boosting the distortion up there. I've come to desiring to see some roll-off starting at the UHF.

It's pretty easy to make a 2425/6/7 titanium sound nasty, for sure....

[norealtalent]

Mr. Talent,

As for both drivers using ferofluids? I was under the impression that the 435Be is not supposed to have ferrofluids in the gap. I assume you bought the 435Bes on the used market? Perhaps the fluid was added?

Have you done any listening comparisons? What horns are you/will you be using with them?

Widget

Thank you Mr. Widget,
Yes, it came used from a man with 4 K2's. Apparently JBL gave him a new driver under warranty and this one was supposed to be DOA. When I got it, there was no output. I pulled it apart to check for the obvious and found none. (It definitely has ferro fluid and I have every reason to believe it was factory. Maybe JBL tried both? I've heard they no longer coat the diaphragms either. I take everything with a lick of salt.) I expected a burt or open coil. I put it back together and put a signal to it and it appears to play perfectly. I suspect one of the contact pins to diaphragm was not located properly on original installation.
I only have the one with a coated diaphragm but have several 2435's I've been playing with for close to a year now. I have been using them on one of my Smith horn pairs on top of my 4343's. I pulled the 2420 out, made a plate to block off the 2307 and ran the wires out the back to the 2435's. I love them. I know the crossover was not designed for these but the 2420/2307 in them sucks. I've had 7 pairs of 4343's and every pair acted the same way, HARSH. This last pair is the first I have biamped and its better but the factory horns just don't cut it. The 2307 is too short and the L91's are not near as smooth as L94's. The Smoth Horns are awesome.
Now I am test driving a 2 way 4648(I think thats the #) cabs loaded with dual 2220's powered by 300 wpc Perreaux SS bottom. I 've got 2360a's on top and 2435's with the 435be back caps powered by 30 wpc Cary EL34 tube amp. Crossover point is 800hz via Urei 525. I'm playing with preamps. I like the Goldentube Audio SEP1 SE best. The SEP3 is too top heavy. My SS perreaux is very nice but the SEP1 takes the cake.
I tried a pair of completely factory 2420's on the 2360's. They were nicer at 500 hz than 800 hz but the 2345's at 800 hz are nirvana for a 2-way. Soon I will run a pair of those ragged cats eyes off a tube amp for some boost in the ultra highs. The 2435's are there but not like a UHF. I am spoiled by the big 4-ways and know that I am sacrificing some things for others in the 2 way but I've had the most joy of listening in the last 2 weeks than I've had all year! Those 2360A's are AWESOME!!!
Someday I'll A/B 2435's w/ factory back caps and 2435's with 435 backcaps on Smith Horns. More on that later... Dave

[Lancer]

Soon I will run a pair of those ragged cats eyes off a tube amp for some boost in the ultra highs.

While the ring radiators are indeed pretty ragged, there are a couple things you can do to improve their overall performance (their ragged response is responsible for their poor decay characteristics). They respond much better connected directly to their own small amp, no passive components between them and the amp whatsoever. The latest word on the old ring radiators is "if you power them directly off a small amplifier (like the small chip amps you can get now) they can sound quite amazing".

[Guido]

I want to re-fresh this thread as I own two 2435 Drivers now and think about aquaplasing or non-aquaplasing the diaphragms.

This I found at the JBL website
K2-Series:
The result is the 435Be, a 3-inch (76mm) compression driver of pure cast-beryllium, capable of unequalled high-frequency response.
• The 3-inch (76mm), Aquaplas-coated diaphragm – the first of this size for JBL – has pistonic motion beyond 15kHz.
• To reduce weight, the aluminum ribbon wire of the voice coil is attached to a one-piece, molded-edge coil support. Together, the voice coil and diaphragm comprise a moving mass of just 0.044 oz (1.25g).

The question is now
2435 = pure Be dia plus Ferrofluid
435Be = aquaplased coated Be dia w/o Ferrofluid

So the 2435 with Ferrofluid plus added aquaplas might be a bit to much damped.

What do you guys think?