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Electro-Voice 848 CDP Horns, remember these?

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Dan Brandesky:
Just wondering if anyone has fond memories of these horns. I don't have any pics, but here is a link to the Engineering Data Sheet. I found 4 of them in a local shop, 3 of which still work. I'm thinking of buying one and maybe offering them a smaller amount for the non-working one, I'm guessing it's a blown driver (what else could it be, it's a horn). I couldn't find any info on the driver but I'm assuming it can be repaired. Anyone have thoughts/memories on this one?

-Dan

Art Welter:
Dan Brandesky wrote on Wed, 23 December 2009 15:24
Just wondering if anyone has fond memories of these horns. I don't have any pics, but here is a link to the Engineering Data Sheet. I found 4 of them in a local shop, 3 of which still work. I'm thinking of buying one and maybe offering them a smaller amount for the non-working one, I'm guessing it's a blown driver (what else could it be, it's a horn). I couldn't find any info on the driver but I'm assuming it can be repaired. Anyone have thoughts/memories on this one?

-Dan


The Electro-Voice 848 CDP Horn is a good sounding wide range public address loudspeaker.
Compound Diffraction means put the horn vertical (the taller way) for the wider dispersion axis to be horizontal.
For the size/SPL/power level,the CDP is hard to beat, I can't think of anything better coming down the pike in the last 40 years. The loading of both the front and back of the diaphragm to extend HF was a good trick.

I think diaphragms are still available.



Art Welter

Milt Hathaway:
There's no driver info because it is a permanent part of this horn. EV still makes two different 70V versions: http://electrovoice.com/products/177.html

Depending upon the vintage of the horns you found, replacement diaphragms are likely to be available.

Their size and horn length make them very good sounding horns for Public Address uses.

Dan Brandesky:
Thanks for the info, guys! Art, you mentioned the horn should be oriented vertically to get the greatest horizontal dispersion; how exactly does this work?

-Dan

Art Welter:
Dan Brandesky wrote on Wed, 23 December 2009 21:21
Thanks for the info, guys! Art, you mentioned the horn should be oriented vertically to get the greatest horizontal dispersion; how exactly does this work?

-Dan


The CDP stands for Compound Diffraction Projector, the large and small horn use the diffraction principle fto get wide horizontal dispersion.

From Wikipedia:
“Diffraction is normally taken to refer to various phenomena which occur when a wave encounters an obstacle. It is described as the apparent bending of waves around small obstacles and the spreading out of waves past small openings. Similar effects are observed when light waves travel through a medium with a varying refractive index or a sound wave through one with varying acoustic impedance. Diffraction occurs with all waves, including sound waves, water waves, and electromagnetic waves such as visible light, x-rays and radio waves. As physical objects have wave-like properties (at the atomic level), diffraction also occurs with matter and can be studied according to the principles of quantum mechanics.”

While diffraction occurs whenever propagating waves encounter such changes, its effects are generally most pronounced for waves where the wavelength is on the order of the size of the diffracting objects.”

In the case of many horns that EV made the vertical dispersion is determined by the horn wall angle, while the narrow dimension makes a wider dispersion due to the small opening relative to the wave length.

The JBL Smith horn ( DSH distributed source horn) uses this effect to get wide vertical dispersion out of a very narrow horn, only 1” or 2”  interior vertical height.

Horns with narrow vertical dispersion that are not tall enough exhibit “pattern flip” below the wavelength of the vertical opening. The HF dispersion is determined by the horn wall angle, but at lower frequencies the waves diffract, resulting in a pattern that may go from 30 degrees to 110 degrees over the course of an octave or so.

Art Welter

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