There really is nothing new under the sun (at least when it comes to loudspeaker R&D)

mhardy6647

Some apt comments on the Western Electric 594a FC compression driver from no less than Joe Roberts (of the late, lamented "Sound Practices" magazine).

...594As went on multicells in proto VOT type systems, 300hz LF cutoff. 18" field coil woofers in open back horn baffles. 86 or 91 model 300B amplifiers.

I can look you in the eye and say that the 594A is the BEST compression driver ever made. This was part of the second generation WE engineering coup, the Mirrophonic systems.

These are far more scarce than 555 drivers. They were only out for two years or so before WE abandoned the theater business. A truly cost no object driver. To buy the cobalt used in the pole piece and yoke costs a couple thousand bucks today. These mainly went into large fancy theaters.

I saw an ad for used theater gear in the early 50s and a complete Mirrophonic model 2 system, possibly including the electronics, was listed for what the inflation calculator put at near a quarter million bucks!

No more efficient driver was ever made. Also, a mostly unknown feature of that driver is this: All midrange compression drivers exhibit a mass rolloff starting at about 5-6k. The rolloff on the 594 approaches the theoretical perfect maximum output and is controlled within 0.25 dB, so that when a simple 6dB peaking network is placed in the amplifier (one cap), the output is flat to 13k. An RCA engineer I know told me that they were adjusted for minimum group delay under this condition...in 1934!

I have never heard more amazing HF than out of that driver on a good [h]orn like the 24A./ I have heard triangles and saxophones sound totally freaking REAL and in the room to a scary, totally caught off guard degree.

Yeah the price is nuts but there is BIG money chasing this stuff. Not for the AK thrift shop and trashpick crowd unless one gets REALLY lucky...ever more unlikely in the look it up on the iPhone era.

Being a man of the people, I settle for ALTEC, but I know that the Western Electric Mirrophonic is the real stuff.

Here's a vid of the WE M2 at Munich HighEnd.

https://youtu.be/o4TNQ7Lin3k


We had major room probs that year, squeezing a speaker for a 3000 seat theater into a small showroom, but we did it.

Here's another vid that features me drinking an alcoholic beverage, a rare occurrence!

https://youtu.be/c0Zja3iAkeE

source: http://audiokarma.org/forums/index.php?threads/western-electric-594a-field-coil-compression-driver.686385/page-2#post-9174081

cnh

Nice tunes!

Man of the people? That's the BEST part! Good Audio for everyone, albeit such drivers are only available as "vintage" these days. And, as stated above, present day costs of manufacture would be prohibitive. But hey, if you can find them, why not?