JBL 2445J diaphragm

[lgvenable]

I've seen discussion of the application of aquaplas to the 2445J diaphrapm. Does anyone have the detail/ like applied to the cone etc, at what number of gsm grams/cm2?

Its pretty straight forward to add water and then use a small sprayer to apply the Aquaplas after mixing down and shearing well with a cowels mixer to achieve a spray-able consistency with little air. I've down that with some of the heavier trowel-able Aquaplas product from Blanchard Chemical.

Who's done this and what advise can you give. At what dry film weight does the addition tone down the aluminum diaphragm from sounding so harsh? Whats the best x-over point for a 2445H and 2206H combo?? (500hz)....used with active mixing via a mono-triamplified amp.

Also, I've already searched but didn't find the small enclosure (volumes) recommendation from JBL for various drivers (2202,2204,2206 etc), can someone throw in a link?

[kevinkr]

I thought the 2445J diaphragm was titanium? Perhaps changing to a Radian 1245-16 is an option?

I've heard a little bit about applying aquaplas, but don't know anyone who has done it. I'm running D16R2445 diaphragms in my 2440 so I am curious about the whole diaphragm issue myself.

Edit: I cross at 800Hz and think the sound is relatively smooth with a pair of relatively non-descript fiberglass 16.5 x 5.5 exponential horns. Perhaps you could cross higher and reduce the diaphragm excursion would should reduce the harshness a bit? (It's a thought and I am not totally sure it would help, and as I am a newbie you might take this with a grain of salt..)

[robertbartsch]

do a search as it has been discussed here more than once

....my solution was to use a UHF tweeter above 10K which elliminates the Ti hiss. The driver rolls off a bit here anyway so the big 2445/6 is really not suitible in a two way system.

[kevinkr]

do a search as it has been discussed here more than once

....my solution was to use a UHF tweeter above 10K which elliminates the Ti hiss. The driver rolls off a bit here anyway so the big 2445/6 is really not suitible in a two way system.

Yeah I am crossing from the 2440 to a 2402 at 8kHz, so I am completely with you on the need to use this in a 3 way system. My set up sounds pretty smooth, so I am debating the wisdom of acquiring Radian diaphragms (1245-16) which seem in recent research not to be universally liked. Always something..

[SMKSoundPro]

I am also crossing the 2402 at 8Khz (using 3-way active crossover and Crown Macro 600) from the 2445/2385 driver-horn combo (using the 600 channel of Crown Macro 24X6) here in the ballroom. Scotty Fitlin was going to send me a pair of used Radians to try, but that never materialized.
I am very curious to try the Radians, or find some 2441 diaphragms which, I believe, would sound better.
I also had a lead on a pair of 2450SL 'phragms from a forum friend here, and am still considering that option, but will need four of them.
If you find out more about Aquaplasing your own homebrew coatings, can you please share your results?
Thank you!!!
Scotty.

[kevinkr]

That is quite the speaker project. I am continuously impressed by the workmanship I see on this forum.. Makes me feel like the amateur I am..

[spkrman57]

That is quite the speaker project. I am continuously impressed by the workmanship I see on this forum.. Makes me feel like the amateur I am..

If I could do woodworking I would be rich!

I have to use cabinets built by others.

Ron

[lgvenable]

Interesting ; I'm all set to set up my fronts now as mono-triamped using 2206H's in 4636 cabinets crossed at an as yet undetermined x-over point with a custom cabinet containing 445J-2385's, cross at 7 or ? 8 KHz to my 2404H's. The cabinet can be slid back and forth to get the correct time alignment between the 2206's and the mid horns and HF 2404H. In the long run, I'd assumed to use a dBX driverack 260 to enable digital time alignment of the speakers.

I've heard several mentions made of "auqaplassed" diaphragms for the 2445J; but never a return when asked. I've don't the requisite search's, and all I've found was mention of aquaplassing. Since its my fortune to have 10 2445J, all in functional condition; I suppose at some point I'd be willing to sacrifice the diaphragm in one.

However it'd be nice to know which side (I'm assuming the front > sound delivery side > which would make the most sense; as the structure of the aquaplas as best I can ascertain is that it is a bulked silica pigment, used to reduce resonance (or in the case of an aluminum diaphragm) reduce the shrillness of the sound?

It's also be nice to know the approximate applied weight. I suppose if I could interest anyone with the proper equipment, via the shuttling of a single diaphragm back and forth, between Indiana and where the measurements were made...then the ideal application weight of aqualplas could be determined after making the proper measurements.

Certainly I can get another sample from Blanchard; but in my first sample four years ago or so, its a thick trowel-able mixture they sell, which must be cut to spray-able consistency. Its about an 18000 cps mixture, what I used to love to call "bag-bottom paste" after the worst glues I ever saw that were used industrially. It was very thick and requires significant reduction with water to get to the proper spray-able consistency.

However since no one ever volunteered a weight, or a method, aquaplassed diaphragms for a 2445J are kind of like urban legends to me.

This offer stands, if anyone out there has the proper equipment, and is willing to work on a project in determining the correct weight on an aluminum diaphragm. I'll donate the diaphragm, and shuttle it back and forth until after each application at a known weight (that's assuming I can remove it from the diaphragm after application.) I'd assumed a application weight of approximately 2 gsm; slightly less than used in a bible, 25% of the weight of a typical sheet of very thin type writer paper.

On the other hand, if anyone out there has two or three older Al diaphragm's which are good enough to determine the weight; but old enough that they'd sacrifice then for a cause, then I'm game to make the aquaplas down to a spray-able consistency, apply it at a known weight, (two or three known weights), and help to figure out how to make aquaplassed Al diaphragm's. In the end we could give anyone interested a procedure for making it, how to spray it, and the results of the investigation. I'll still donate a single diaphragm to that cause as well.

Its kind of like what I do everyday, except it'd be fun to provide the info to the forum to support work on modding aluminum 2445J diaphragms.

[subwoof]

The subject of damping requires a bit of backward thinking. The goal ( as stated by JBL ) of "damping spurious resonances" of the diaphram by coating it means that some undesired "ringing" must be occuring at frequency(s) at least 1/2 of the measured annoying one.

This would mean that even adding a tweeter would still allow the fundamental "issue" to be present ( but albeit not as noticeable ) in the midrange's output.

There are probable many different points where the diaphram might ring so damping seems to be a good way to keep them somewhat behaving without resorting to filters and such.

All my 4" coils are damped on a variety of horns but the larger 2352 horns, with their resulting larger air mass, really work better than the short ones no matter what the diaphram.

sub

[Robh3606]

This offer stands, if anyone out there has the proper equipment, and is willing to work on a project in determining the correct weight on an aluminum diaphragm. I'll donate the diaphragm, and shuttle it back and forth until after each application at a known weight (that's assuming I can remove it from the diaphragm after application.) I'd assumed a application weight of approximately 2 gsm; slightly less than used in a bible, 25% of the weight of a typical sheet of very thin type writer paper.

It's not going to happen unless you take it out of the holder and have a very high resolution scale. Better off just thinning and brushing it on.

Rob

http://www.audioheritage.org/vbullet...ead.php?14236-AQUAPLAS

http://www.audioheritage.org/vbullet...th-a-turntable

http://www.audioheritage.org/vbullet...Damping-Agents

[grumpy]

... and/or buy one or two 2450-SL diaphragms (2445 rib-less titanium w/ aquaplas already
applied) for reference. (measure/compare impedance curves and signal amplitudes)

[Robh3606]

(measure/compare impedance curves and signal amplitudes)

You need to look at the ETC curve/decay to see it.

Rob

[grumpy]

Ah. I have both somewhere (-SL's might be 8 ohms though... otherwise, I should do this
for my own satisfaction). Thanks

[4313B]

It's not going to happen unless you take it out of the holder and have a very high resolution scale. Better off just thinning and brushing it on.

Right. As I've mentioned numerous times, two thin coats, the first one will be insufficient and the diaphragm should "show through" it. The second coat, applied after the first is dry, should cover the diaphragm completely so it doesn't "show through".

The aquaplas should be thinned with water. It is not the same thickness as one would use on a woofer cone. A model brush is best. There is no reason to bother with a sprayer unless you are doing large quantities of diaphragms.

If you get heavy handed with the stuff it will ruin the endeavor.

The D8R2452H-SL (4-inch cores) is probably the best bet for anyone who doesn't feel like doing their own. They're awfully cheap so buy a bunch and have at it. I think JBL has made more of the D8R275ND (1.75-inch cores) available again as well but I could be wrong and don't have time to check right now. Just call Harman Parts and ask. These are the cheap solution. The TruXtent are arguably the best solution but I think they are three to four times more expensive (well worth it for those who care about such things).

[spkrman57]

The TruXtent are arguably the best solution but I think they are three to four times more expensive (well worth it for those who care about such things).

At first I had doubts about the cost for Be diaphrams, but I'm glad I took the chance as they exceed any Al or Ti diaphrams I have heard before, well worth the cost!

Regards, Ron