Harold Beveridge ESL's

[dono]

Newbie here!

Anybody know what happened to the speaker company named after it's late designer?? This was a Santa Barbara-based company.

Thanks,

Don

[phase_accurate]

why dont you just consult their homepage ?

http://www.beveridge-audio.com

Regards

Charles

[dono]

Charles-

Found their website, and phoned the company, which is now run by Harold's son, Rick.

Glad to see that they're back in business. Their ESL's are pricey, but very sweet sounding.

Thanks for the link.

Dono

[johnkramer]

has anyone used "aluminized Mylar diaphragm" in DIY yet?

Originally posted by phase_accurate
why dont you just consult their homepage ?

http://www.beveridge-audio.com

Regards

Charles

[phase_accurate]

With ordinary electrostats one likes to keep the charge on the diaphragm from "wandering around". That's why high-resistance coatings are preferred.
Low-resistance coatings may possibly work with very narrow or small ESLs.

Regards

Charles

[I_Forgot]

Originally posted by johnkramer
has anyone used "aluminized Mylar diaphragm" in DIY yet?

Metalization causes a couple problems. The low resistance allows the charge on the diaphragm to move around which untimately results in distortion.

ESLs sound so nice in part because they are normally very low distortion drivers. The low distortion is a result of the entire (well, OK, most of) the diaphragm being driven, unlike a cone speaker that is driven from the center and relies on the stiffness of the cone to behave like a piston.

Why would the charge move around? When the diaphragm is deflected toward one stator or the other, the electric field between the two rises. The diaphragm deflects the most where it is easiest- at the center (the edges are held firmly and can't deflect) so the charge will make its way to the center of the diaphragm where the E field is strongest. Where does the charge come from? The rest of the diaphragm (remember there is a big resistor between the HV bias supply and the diaphragm, so it can't come from the bias supply). When the charge moves away from the outer part of the diaphragm toward the center, what is driving the outer part of the diaphragm? That's right! Nothing! That is why it will distort.

What if we just used a low resistance between the bias supply and the diaphragm? In that case, when the diaphragm moves the charge will again move to the center, but now there will be more charge available. So it will still distort. What about the extra charge? It will do it's best to jump across the now small gap between the diaphragm and stator. If it is successful, you will see a spark, hear a popping sound, and if you're really lucky, the diaphragm won't burst into flames.

That brings us to the second problem with metalized diaphragms. Polyester is ordinarily self-extinguishing. Add a layer of metal, and it becomes inflammable. Don't believe metal burns? Try burning a steel wool scouring pad.

High resistance coatings essentially keep the charge on the diaphragm immobile. A medium resistance coating will allow the charge to move somewhat, and low resistance coatings will allow it to go wherever the E field wants it to go. A driver that is intended for low frequency reproduction needs to have a high resistance coating because low frequencies cause the diaphragm to deflect the most, thereby causing the charge to try to move the most. If the speaker is only intended for high frequency reproduction, you can get away with a lower resistance coating because high frequency content of music doesn't cause the diaphragm to deflect much.

A diaphragm with a low resistace coating can be used for high frequency reproduction, but isn't very good for low frequencies. A diaphragm with a high resistance coating can be used for low frequencies as well as high frequencies, so usually people just use high resistance coatings when they make ESLs.

I_F

[bobbo]

That was informative and worthwhile reading . More of that.

[wytco0]

Glad to see that they're back in business. Their ESL's are pricey, but very sweet sounding.

You could say they are pricey "The retail price for a basic Model 2 system, including OTL amplifiers and shipping (worldwide), is $65,000 per pair. "

At least you dont have to pay for shipping

[dono]

I worked for the company back in 1978 in Santa Barbara, CA.
The price for a pair of the Model II's was $10K, and I thought that was pricey.

I couldn't afford them then, and I can't afford them now. I really think they should re-think their prices!

Dono

[phase_accurate]

The price for a pair of the Model II's was $10K, and I thought that was pricey.

That's about the time when I heard a pair at an exhibition in Switzerland. Here the price was almost twice that much (as almost everything from the U.S. like cars, Maglites, Weber barbequeues .....)

Regards

Charles