Victor Orthophonic Exponental Horn Design

[phononut]

Hello
Well, I have allotted many parts and a long time ago I dreamed of making my own phonograph out of all of them, in hope to make a super good sounding machine. All the parts I plan to use are really junky. They are all rusty and require much tender loving care to make them even functional, so I do not see a problem with making sort of a homemade frankenphone. Anyways I did some searching and I came across the awesome video on YouTube. The main stated that he built the machines horn form measurements from eBay auctions etc... I looked around with no luck. Also I am a bit confused of the general design of an exponential horn. If someone can help me out here maybe with some measurements and diagrams that would be much appreciated.

Thanks
Brad

http://www.youtube.com/watch?v=zm7k6ZIeCAo

[David Spanovich]

There was a discussion of that horn, awhile back, on this forum:

http://forum.talkingmachine.info/viewto ... 91&start=0

I originally posted it under my "old name."

The person who built that horn, as noted in the post string, is a member of this forum, so you might want to send him a private message to see if he still has the measurements that he could share with you.

The link to the gallery of photos showing the horn under construction, which he included in his post, is no longer working, but perhaps he still has them.

Keep in mind, the folded exponential horn represented a compromise, since the designers--Joseph P. Maxfield and Henry C. Harrison of Bell Labs--had to fit it into a cabinet that would be small enough to be accommodated into the average size living room (parlor?) of the late 1920s. Ideally, a well designed exponential horn should have very few bends in it. The ultimate version of this was the type of horn produced by EMG and E.M. Ginn for their hand-built gramophones.

Another member of this forum created his own version of the (giant) external exponential horn gramophone, as described in this post:

http://forum.talkingmachine.info/viewto ... f=2&t=6065


HTH,
DS

[syncopeter]

Nice as the folded horn is, for the best sound production nothing will match a true unfolded exponential horn. The gramophone built by Odeon proves that.

[JohnM]

The term 'Orthophonic' literally means 'straight sound', only somewhat ironically.

[1926CredenzaOwner]

!

[syncopeter]

The Victor scheme would mean that the 'wooden' one is not a true orthophonic, since the horn is only folded once, like HMV's model 157. It would be a heck of a job to create a doubly folded horn from wood in this size, unless you used very thin triplex (as victor did for their first orthophonic models).

[Odeon]

Here are some things, that helped me a lot to create my "Big Bertha" horn

First, in the fine book "Modern Gramophones & Electrical Reproducers" by P. Wilson from 1929, there is a whole chapter about horn design - everything (and more ) you ever want to know about the making of good sounding horns...

Here is the index of the "horn chapter"

Horn index.jpg (110.89 KiB) Viewed 4957 times

and a example

Via this link you can download the article as a pdf
(sorry about the bad quality - I haven´t a scanner, so I made this with my digi-cam...)
http://www.box.com/s/rglujz0n7t5cksnb525k

Another fine tool is the little program "BassCADe".
It is made for calculating horn speakers, but is also very helpful for calculating exponential Gramophone horns.

This is how the working program look like, while you calculate a exponential horn

screen.jpg (184.22 KiB) Viewed 4955 times

You can download the program as a zip file via this link:
http://www.selfmadehifi.de/basscad.htm

It is made from a german guy, but here (maybe read this before downloading) are the FAQs about the program in english:
http://www.selfmadehifi.de/basscad.htm#FAQs_en

[David Spanovich]

The Victor scheme would mean that the 'wooden' one is not a true orthophonic, since the horn is only folded once, like HMV's model 157. It would be a heck of a job to create a doubly folded horn from wood in this size, unless you used very thin triplex (as victor did for their first orthophonic models).

The term "Orthophonic" was simply a marketing term, or "brand name" for the Victrola line produced during this period, and did not describe the tone chamber, itself, or the basic principal behind the design, which was referred to as "matched impedance" by the original designers. All of the Victrolas equipped with exponential horns/tonearms & sound boxes were "Orthophonic," including the Consolette which used the straight or "non-folded" exponential horns, as did the portable models.


Also, the illustrations of the Victor exponential horns DO show that the horn is divided into four sections--look carefully at the "heart," where the chamber is divided in two sections in BOTH the upper and bottom portions.

A number of Orthophonic Victrola models did use horns divided into two sections, such as the later-style Granada models, the 4-7, etc.

DS

[syncopeter]

HMV used the term re-entrant only for the horns that had 4 sections, i.e. that were folded into themselves. The model 157 and its successors were not regarded as re-entrants. All models having the logarithmic horn and the 5a/b soundbox were described as built using the 'matched impedance' principle, even the humble table model 103.
Did Victor use orthophonic for all its models with an exponential horn?

[David Spanovich]

Did Victor use orthophonic for all its models with an exponential horn?

Yes, all of the Victrolas equipped with exponential horns/tonearms & Orthophonic sound boxes were "Orthophonic," as noted in my post above.

DS