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ratitifb
11-27-2008, 02:06 PM
Hi Folks

a 044 pair just got home and the silver coating on one dome is flaking :(.

Is there any sounding issue ?

Has anyone ever successfully refinished these ?

Any ideas? Thx ;)

rdgrimes
11-27-2008, 03:38 PM
Best idea is to replace it. Without the aluminum coating it's not really doing it's job.

BMWCCA
11-27-2008, 05:10 PM
Best idea is to replace it. Without the aluminum coating it's not really doing it's job.What I've heard is the "deposited aluminum" is really a sort of spray paint.

According the JBL, the dome of the 044 is made of a "lightweight phenoloc material, coated with aluminum by means of a vapor deposition process". I don't think you can hurt it by carefully cleaning it up and spraying it with a fine coat of silver or aluminum spray paint. What have you got to lose?

Baron030
11-27-2008, 09:59 PM
Since, one of my hobbies is astronomy and I have even made my own telescope optics. I know that aluminum is far too reactive to be chemically deposited on to a surface. So, deposited aluminum is not really like any spray paint. Instead, a physical vapor deposition process is used where the object to be coated is placed in a chamber and a hard vacuum is pulled down. After all of the air is removed, a small aluminum strip is heated to a point where it will then vaporize. These aluminum vapors will then condense on any cooler object. In a way, most of you have already seen this vapor deposition effect, without really knowing it. One of the reasons why an incandescent light bulb fails is because tungsten from the filament is vapor deposited on the inside surface of the glass bulb, which is why the glass on very old clear bulb will look kind of dark and cloudy.

Here is a link to a video explaining the aluminum vapor deposition process as it refers to telescope optics.
http://www.youtube.com/watch?v=9K49pVEEDwA (http://www.youtube.com/watch?v=9K49pVEEDwA)

Admittedly, applying an aluminum coating on a JBL 044 dome is a lot easier then any optical surface. But, in both cases I would think that these coatings are extremely thin. The coating on a telescope mirror is only 21 atoms thick. So, I would think that even a thin coat of spray paint will weigh a lot more then the original deposited aluminum.

If the driver sounds good, then I would leave it alone.

Baron030:)

BMWCCA
11-28-2008, 05:37 AM
So, what exactly is the surface we're dealing with? Definitions of "phenolic" seem vague to a layman like myself.

Dictionary: phenol |ˈfēˌnl; -ˌnl|
noun Chemistry
a mildly acidic toxic white crystalline solid obtained from coal tar and used in chemical manufacture, and in dilute form (under the name carbolic) as a disinfectant. Chem. formula: C 6 H 5 OH.
any compound with a hydroxyl group linked directly to a benzene ring.

Wiki: The properties of phenolic materials make them very well suited to myriad industrial applications. Phenolics are the result of polymerization (http://en.wikipedia.org/wiki/Polymerization) between resin and a base material that can be paper (http://en.wikipedia.org/wiki/Paper), glass (http://en.wikipedia.org/wiki/Glass) or cotton (http://en.wikipedia.org/wiki/Cotton). The base material used is dependent upon the intended application of the finished product. Paper phenolics are used in the manufacturing of electrical components such as punch-through boards and house hold Laminates.

My guess would be that the dome material is closer to plastic than to metal. You can airbrush a far lighter coating than you can with commercial rattle-can paint. Is the coating actual providing a damping effect on the 044, or is it just to make it look like metal? :dont-know

Baron030
11-28-2008, 08:05 AM
Is the coating actually providing a damping effect on the 044, or is it just to make it look like metal?

That is a very good question. It is very possible to deposit a thick and relatively heavy coating of aluminum to the phenolic substrate, which could alter the acoustic properties of the dome. But, I could equally wager that its done just to make the dome look like metal.

So, if the driver sounds good, then dont fix what is not broken. The aluminum coating must be just cosmetic. But, if the driver does not sound right then no amount of spray paint will fix that problem.

Baron030:)

4313B
11-28-2008, 08:27 AM
The 033 had the black painted dome and was "softer" than the 066 with its "brittle" aluminum dome via vapor deposition.

The story goes that when the vapor deposition machine final broke at JBL they didn't bother to fix it and resorted to paint. I remember hearing that the silver and gold 044 and 044-1 domes were painted. To spray the paint on one would probably have to use a model paint sprayer and make sure the layer was quite thin. Perhaps hand painting them would work better.

Or just leave them bare phenolic as suggested above.

BMWCCA
11-28-2008, 09:15 AM
I've got one of these somewhere, under $20 (plus an air can) and the appropriate paint:

http://www.amazon.com/250-Spray-Gun-Basic-Carded/dp/B0006MZPLG
http://ecx.images-amazon.com/images/I/51yx80BIiXL._SL500_AA280_.jpg

Mr. Widget
11-28-2008, 09:35 AM
Has anyone ever successfully refinished these ? Define successfully. :)

A number of years ago I sprayed Mirra Chrome onto a forum member's 033 or 044... can't remember which. It looked a lot like yours... afterwards it looked better, but not perfect. Mirra Chrome is part of a paint system that deposits extremely fine aluminum powder onto a substrate and creates a look very much like chrome. I used it in my model making business to create chrome accents out of plastic parts... http://www.alsacorp.com/products/mirrachrome/mirrachrome.htm

It kinda sorta worked... the aluminum powder is finer than the aluminum you'll find in any paint and is held in a very thin ethylene alcohol suspension... when it is sprayed the solvent quickly flashes off and you are left with a fine aluminum deposition... if you spray it on a highly polished surface it will look like chrome. If the surface has a fine matte texture it'll look like matte aluminum. Unfortunately the cloth texture of the JBL tweeter I coated was coarser than a fine matte texture and this texture continued to show through the aluminum film... that said, an aluminum dome even with that texture looked better than the dark areas that had been showing through.


Widget

BMWCCA
11-28-2008, 10:58 AM
The dome in the original post looks more like something got stuck to it, rather than a coating failure? Do we know the history? Language issues sort of imply they are new to the owner. Screens missing might explain coming into contact with something. Just curious. Might try a careful cleaning first?

Mr. Widget
11-28-2008, 11:40 AM
The dome in the original post looks more like something got stuck to it, rather than a coating failure?The one I worked on looked the same way... that is the phenolic impregnated cloth showing through. The aluminum coating is simply worn away.


Might try a careful cleaning first?...and remove all of the aluminum? :no:


Widget

ratitifb
11-28-2008, 12:44 PM
very interesting replys. Thanks to all ;)


The dome in the original post looks more like something got stuck to it :no:

actually a coating failure really



...and remove all of the aluminum? :no: :no:

The aluminum coating seems to be cosmetic mainly and i'm thinking not for damping effect (metal vs phenolic ...)


If the driver sounds good, then I would leave it alone.:yes:

rdgrimes
11-28-2008, 01:11 PM
The aluminum is not just cosmetic, it's there for it's rigidity and radiating quality. At the time, there was no way to economically construct a dome of aluminum like we do with titanium today, this process was the compromise. This dome was designed with aluminum in mind. I stand by my statement that it should be replaced. The best analogy I can think of is the poly coating on woofer cones. You can peel off all the white poly coating on the old woofers and say it's just cosmetic because they still work. But that doesn't make it so.

BMWCCA
11-28-2008, 01:51 PM
So the term "phenolic" is vague enough that the base material could even be closer to cloth than plastic? I can see now, I'm gonna end up dissecting one of my spares just to get to the bottom of this. I know, "Take lots of pics!" :applaud:

grumpy
11-28-2008, 02:32 PM
I stand by my statement that it should be replaced.All well and good, but with what? Last I understood the kits were NLA.
Otherwise, I'd agree. In this case, what's to lose? Get another, better
example on Ebay if it gets damaged or sounds like crap afterward.

BMWCCA - Phenolic is the material the cloth (linen?) is embedded in... sort of
like glass cloth in fiberglass.

BMWCCA
11-28-2008, 02:50 PM
BMWCCA - Phenolic is the material the cloth (linen?) is embedded in... sort of like glass cloth in fiberglass.So what's peeling off? Keeping with the fiberglass analogy, is the "aluminum" "deposited" over a smooth finished cloth, like over the resin "gel coat"? Is it the binder coming apart and taking the "aluminum" with it? Like maybe the dome got smashed and poked back out, thus cracking the "resin"? The "aluminum" other than the part one would expect to be smashed looks fine. That's partly why I asked the OP to give us some history of this 044.

Just curious, but I do have a spare that needs to be "sucked" out.

grumpy
11-28-2008, 03:00 PM
yeah... the aluminum is flashed on over the phenolic/cloth layering.
(or painted on)
That the phenolic/cloth sandwich is so thin is why you see the cloth
texture coming through. With the Al coated domes, you can actually
see the texture a bit better (perhaps thinner and more conforming to
the surface).

If it was pushed in, it was irreparably damaged... not that it can't sort of
work in an Ebay "doesn't affect the sound at all" sort of way.

Mr. Widget
11-28-2008, 03:45 PM
BMWCCA - Phenolic is the material the cloth (linen?) is embedded in... sort of
like glass cloth in fiberglass.Yes, phenolic resin... is used here just like polyester or epoxy resin is used with woven glass for fiberglass boats.


Keeping with the fiberglass analogy, is the "aluminum" "deposited" over a smooth finished cloth, like over the resin "gel coat"?Exactly.


So what's peeling off?The aluminum is simply flaking off.


Widget

rdgrimes
11-28-2008, 04:00 PM
So the term "phenolic" is vague enough that the base material could even be closer to cloth than plastic? I can see now, I'm gonna end up dissecting one of my spares just to get to the bottom of this. I know, "Take lots of pics!" :applaud:

It looks and feels like a dacron fabric to me. I have several that are aluminum-less. They feel completely different without the aluminum, very soft.

4313B
11-28-2008, 04:18 PM
All well and good, but with what? Last I understood the kits were NLA.I don't agree with JBL about discontinuing these kits. There are alot of the systems still out there in the field and they still sound very nice.

SMKSoundPro
11-29-2008, 04:02 AM
I don't agree with JBL about discontinuing these kits. There are alot of the systems still out there in the field and they still sound very nice.
BUT>>>

They are.

Why can't we spread on some goo glue kinda stuff, then grab some of the wife's coveted ALCOA aluminum wrap from the drawer she hides it in, then start to work over the dome, just like a resin coating on a boat hull. I think I saw this once on the Science channel - "How it's Made." Certainly it should work and sound fine?

I've got a DOA 044 phragm just waiting to come back to life in a "Myth Busters" kind of way!


NO WAIT!

That's a dumb idea.

Sorry.

scotty.

see post: http://www.audioheritage.org/vbulletin/showthread.php?t=22546&highlight=044

ratitifb
11-29-2008, 06:24 AM
The aluminum is simply flaking off.:yes: again


The aluminum is not just cosmetic, it's there for it's rigidity and radiating quality.i probably agree with that :)

At the time, there was no way to economically construct a dome of aluminum like we do with titanium today, this process was the compromise. regarding such alu dome like D16R2420 or D8R075 dias (except surrounding shape) what was the problem :rolleyes: ?


see post: http://www.audioheritage.org/vbulletin/showthread.php?t=22546&highlight=044 i read that very interesting post ;) before and it was the reason of my 2nd question "Has anyone ever successfully refinished these ? "

But it sound better to leave my 044 alone :hmm: when the coated dome is partialy masked by the front metal grid ...

Mr. Widget
11-29-2008, 09:53 AM
regarding such alu dome like D16R2420 or D8R075 dias (except surrounding shape) what was the problem :rolleyes: ?Economics...

JBL did build and aluminum domed direct radiator called the LE30 in the early '60s... it was just too damned expensive.


Widget

4313B
11-29-2008, 10:12 AM
Economics...

...it was just too damned expensive.Which is also why they are moving to magnesium diaphragms in their compression drivers instead of beryllium.

timc
11-29-2008, 12:15 PM
Really?

How does magnesium compare to beryllium and titanium quality wise?


-Tim

Mr. Widget
11-29-2008, 12:35 PM
How does magnesium compare to beryllium and titanium quality wise?The ideal diaphragm is infinitely stiff and massless.

Beryllium is the closest to that ideal followed by Magnesium and Aluminum... Titanium is the least rigid for a given mass...

This is why JBL is now using a lot of AL diaphragms in their current high end home speakers. Years ago they stopped using Aluminum diaphragms in their pro compression drivers due to mechanical failure during prolonged high power use.


...and once again we have drifted a bit off topic. :)



Widget

rdgrimes
11-29-2008, 01:17 PM
The ideal diaphragm is infinitely stiff and massless.

Which to me says that a 044 dome without it's intended layer of aluminum is broken and should be replaced.

4313B
11-29-2008, 01:49 PM
...and once again we have drifted a bit off topic. :)Thankfully so... one can only chat about an 044 dome for so long...

Thanks for the post with respect to the various diaphragms. Oh, and they are dusting the magnesium diaphragms for those who are horrified by such things. I suppose I should have waited until next Halloween for the fightening revelation but oh well... Boo!
Which to me says that a 044 dome without it's intended layer of aluminum is broken and should be replaced.Like I said, without the aluminum it kinda sorta becomes a slightly more powerful 033... just do what JBL suggested when this came up the last three or four times and put a thin coat of nice aluminum paint on them. If you screw them up you'll know it right away.

lgvenable
08-14-2010, 08:46 AM
BMWCCA
Phenolic polymer refers to a phenolic polymer oligimer, which is catalyzed and thermally cured. These are very durable and water/chemical resistant. The same type polymer s used on hard to hold food , beverages, beer and other rigid packaging cans product side, which is the side exposed to the food we eat. Hard to hold, as fats and fatty food are tough to hold since they attack most polymers and soften them. Pet food, people food etc. The same type just different formulation is used on the public side (outside of the can,); just with different packages in it to help the coating survive the can forming processes.

These are also known as BPA based epoxy coatings.....which some tree huggers are out to ban.
See:
http://en.wikipedia.org/wiki/Bisphenol_A

btw this is what I help coat at Alcoa onto aluminum everyday, while I work on new non-epoxy based coatings to replace these. Trouble is lots of NGO's are against these emotionally (non governmental group); but rather than base an opinion on science we have had around for 50 years, they call it a "toxic chemical" and want to ban it. The FDA, European FDA, Japanese FDA all say "they;re safe".....but then again the NGO's have public opinion.....

OK OK end of a rant by a coating scientist.... Frankly BPA or BPA free...pays my salary either way; and keeps me off the streets at night......;)

If it sounds OK, why not leave it alone; either that or replace it, otherwise you're putzing around and might wreck the response. If it sounds right but aint pretty whats the difference?