Victor Orthophonic Horn Designs

[JerryVan]

I'd like to understand more of how the Victor people developed their design. I suspect it was an interesting mix of science, trial and error, and ultimately intuition.

Before 1925, it was trial & error and intuition. After 1925, it was science. Basically, in 1925 it was discovered that the laws of physics and the formulas that describe electricity, are also valid for sound. Designers then had a mathmatical tool with which to design horns, tone arms and reproducers. That's my basic "Orthophonic Horns for Dummies" speech, (because that's the sum total of my understanding of them). Others will undoubtedly refer you to several texts from the era that can describe these horns in excrutiating detail.

[TN Allen]

"excrutiating detail" regarding the Victor Orthophonic horns is just what I want. Particularly dimensioned drawings and photographs.

I have read some of Modern Gramophones and Electrical Reproducers, which explains some of the basic science, but it is the Orthophonic information I'd like.

[OrthoFan]

... I'm only interested in seeing and understanding the Victor design....

This might provide a clue as to the intricacies involved in the re-entrant folded horn design -- https://www.youtube.com/watch?v=fYrS2oLsJ3s
The horn in the video is culled from the VV-4-40, and is a smaller version of the four chamber re-entrant style horn used in the Credenza. The overall length of the tone chamber, including the tonearm, is about five feet. The horn's mouth measures 16 inches by 16.5 inches.

The Orthophonic sound box and horn were not designed by Victor, but by Western Electric (Bell Labs) designers -- Joseph P. Maxfield and Henry C. Harrison. Victor was granted exclusive use of the design under a licensing agreement.

Here's the patent information for the folded exponential horn, as used in the Credenza:

US1747830.pdf

(670.3 KiB) Downloaded 74 times

Hope this helps,
OrthoFan

[TN Allen]

Thank you, this is wonderful.

[HMVDevotee]

OrthoFan,

Thanks as well for the Bell Labs patent application.

I wonder if anyone has the specifications (drawings, etc.) for the HMV variant executed in metal. I think I read somewhere that the HMV re-entrants included "narrower radius" turns in order to reduce radius lag and the consequent frequency distortion, but I can't recall where I came across it. As I recall, the outside radius wasn't necessarily shorter. The horn, in cross-section, was narrower for the same comparable radius, allowing less of a variance between the inner and outer radius of the horn's "bend", and that the horn's other dimension was increased accordingly to accommodate the necessary exponential rate of expansion of the total area. See image as an exaggerated example of the shape discussed. (Credit to the RadioMuseum.org for the illustrative image herein.)

HMVDevotee