Western Electric 594A...Need some input...

[TonyCee]

Hello! Where I come from it is bad form to ask for permission to come aboard immediately asking for something from the crew and passengers. I don't see that I have a choice at the moment. Hopefully you won't find it too terribly in bad taste. I'm asking this question here on this forum based on the advice of a man from another forum I use frequently; he said there are many here that know a lot about old theater type speakers and that a lot of JBL was designed after WE components. I have read some evidence of this on the web.
I recently came across a Western Electric 594A compression driver. I opened it up and found the diaphragm to be intact. I have seen pictures of the 594A with gray colored diaphragms, mine has one more like a cream color. I can't say if it has been changed, has discolored, or possibly WE used more than one color diaphragm. That's one thing I would like to know.
Next thing is, I measured DC resistance across the 2 sets of terminals which I believe are the voice coil, the upper terminals, not the ones for the DC power supply behind the door on the 594A. 3 days ago, I measured 300 ohms across the upper terminals, which I have a feeling is all wrong to begin with. I re-opened the unit to look at, and photograph the diaphragm since then, now I measure 450 ohms ????? I wonder if it is possible that I have effected the reading by "pinching" the 2 thin leads from the terminals somehow. I have seen pictures where the 2 sets of terminals, that is the coil and DC power supply were connected with wire leads. I did NOT take my measurements with such leads in place. I measure 18 ohms at the DC terminals beneath the door. Have I measured properly? Of course there was NO power to the driver when taking my measurements.
I am a bit depressed about this as when I found the driver recently I really thought it would help a dire financial situation at home. I'm also wondering if there is something wrong with the coil can it be remedied? I should mention the driver is in nearly perfect condition and I see no evidence of exposure to elements ( the exit side was covered and screwed shut) or other abuse. Hopefully someone can help. Thanks everyone, and I apologize for the rude entrance here....Tony

[herki the cat]

QUOTE=TonyCee;220604]Hello! Where I come from it is bad form to ask for permission to come aboard immediately asking for something from the crew and passengers. I don't see that I have a choice at the moment. Hopefully you won't find it too terribly in bad taste. I'm asking this question here on this forum based on the advice of a man from another forum I use frequently; he said there are many here that know a lot about old theater type speakers and that a lot of JBL was designed after WE components. I have read some evidence of this on the web.
I recently came across a Western Electric 594A compression driver. I opened it up and found the diaphragm to be intact. I have seen pictures of the 594A with gray colored diaphragms, mine has one more like a cream color. I can't say if it has been changed, has discolored, or possibly WE used more than one color diaphragm. That's one thing I would like to know.
Next thing is, I measured DC resistance across the 2 sets of terminals which I believe are the voice coil, the upper terminals, not the ones for the DC power supply behind the door on the 594-A. 3 days ago, I measured 300 ohms across the upper terminals, which I have a feeling is all wrong to begin with. I re-opened the unit to look at, and photograph the diaphragm since then, now I measure 450 ohms ????? I wonder if it is possible that I have effected the reading by "pinching" the 2 thin leads from the terminals somehow. I have seen pictures where the 2 sets of terminals, that is the coil and DC power supply were connected with wire leads. I did NOT take my measurements with such leads in place. I measure 18 ohms at the DC terminals beneath the door. Have I measured properly? Of course there was NO power to the driver when taking my measurements.
I am a bit depressed about this as when I found the driver recently I really thought it would help a dire financial situation at home. I'm also wondering if there is something wrong with the coil can it be remedied? I should mention the driver is in nearly perfect condition and I see no evidence of exposure to elements ( the exit side was covered and screwed shut) or other abuse. Hopefully someone can help. Thanks everyone, and I apologize for the rude entrance here....Tony[/QUOTE]

Tony, the defective 594-A voice coil may well be repairable but it takes special skills__ Do not attempt any repairs your self.

Contact:www.greatplainsaudio.com to execute this repair. They still have all the Western Electric 594-A factory tools, the skills, and remaining Altec engineers.

Around 1954, the Altec Service Co. NY, City, sold 594-A for $69.00 with original blue/gray diaphragm which is the most perfect sounding driver. RCA 1930's Photophone HF horns provide full acoustic loading down to 150 Hz which is essential for Zero Horn Honk performance with cross over in the region of 250 to 300 Hz. JBL also manufactured simliar horns.

For what it's worth, a two way theater horn system delivers a huge wave front with excellent uniform frequency response every where in a well designed listening room with 10 watts or less of amplifier power__Single Ended amps, Anyone? The movie theaters prior to the 1950's were capable of magnificent concert hall acoustics with room sound reverberation quality.

The JBL model 2440 is the professional version of JBL permanent magnet model 375 driver. Both of these 594-A clones with identical original JBL Aluminum diaphragms come very close to 594-A.

The actual measurements of 594-A with the blue/grey diaphragm are dead flat up to the mass break point around 7,000Hz with a roll off at 6 db / octave plus or minus 0.1 db all the way to 20,000 Hz.

You can tip up the response 6 db / octave above 7,000 Hz with one RC in the amplifier to provide flat response to 20,000 hz. Performance of 594-A with the "repair" softer "Cream color" aluminum diaphragm come close; however nothing sounds as clean and real as the orignal blue grey version.

The blue /grey diaphragm color which looks like it "just clawed its way out of hell" is due to the Western Electric heat treatment resulting in extreme hardness of the special duraluminum alloy no longer available unless you put up $100,000 up front for production startup.

Cheers Herki The Cat