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Thank you for that. The bi-furcated horn is exactly what is in my Columbia 153a cabinet Grafonola. It does sound OK but the bass could be better. I can see how the bends in the conduit lengthen the horn, although it is hardly a big horn, but not sure about the benefit of splitting the conduit into two equal parts. The 'plano-reflex' horn looks like a better bet. It certainly would have been possible to put a bigger/better horn in the 153a, as there is space enough to do this with a little ingenuity and a few more conduit bends.....

The bifurcation obeys to the principle of division into smaller conduits for making the bends, which is better for matching impedances and phase of the sound pressure waves. The bends must have similar cross section size to the bend radius, etc. It's because in a bend, the paths are of different length at one side or another, so the wavefronts tend to twist across the conduit, and this impacts the sound train mixing different phases and losing clarity, crispness, etc. It's better to divide the conduit into smaller sections and then rejoin them after the bends, still better if the divisions are all symmetrical and of the same lengths. The reading of Percy Wilson's Modern Gramophones and Electrical Reproducers, of 1929, is very illustrative to know the basic principles of sound transmission applied to the gramophone design and construction, first unconsciously, by trial and error and much experimentation, and later consciously, applying the wave transmission laws to the scientific design and construction of the sound conduits and soundboxes.
The design of the Columbia bifurcated horn is a clever one, and the lack of bass is due to the small horn mouth.
Later came the invention of the Plano reflex technique to favour the straightening of wavefronts along the bends by means of clever reflections which maintain the same path lengths across the bends.

The link provided by our colleague downloads the whole book in pdf form.

Thank you for that further information. Several of the horns in this 'Rifanco' ad show the principle of the bifurcated horn: viewtopic.php?p=337891&hilit=Horns%21#p337891

Possibly one of them could be used to improve the bass response of the Columbia 153a - if you can find one. I suspect many of these were used in hand-made gramophones built by enthusiasts back in the 20's/30's, as suggested by the advertising blurb....

All this I find fascinating...

I like both the US and the English horn designs - both perform well, losing only to re-entrants. The physics behind their designs may be obscure, but the end results are very good.

OrthoFan wrote: Mon Jan 27, 2025 10:35 am

An Balores wrote: Mon Jan 27, 2025 8:39 am 'Orthofan' says "The UK manufactured Viva Tonal models were fitted with bifurcated metal horns, but they weren't re-entrant. They were dived into two sections which joined at the mouth."
So is there any benefit to this arrangement? I can't see it myself.....

From the videos on Youtube, there does seem to be an enhancement in sound quality, compared to earlier designs. The UK based collectors would have far more knowledge about this than I do, but essentially, the bifurcated design allowed a much longer--more gradually tapered--horn, with a larger mouth, to be fitted into conventional size cabinets. The horn, which had an exponential style taper, was coupled to a gradually tapered tonearm fitted with a new style sound box equipped with an aluminum diaphragm, as was the case with most other sound boxes produced at that time.

Another design--unique to Viva-Tonal models produced in the UK--employed the "Plano-Reflex" style horn and tonearm. You can find quite a lot about this online by doing a search for Columbia Plano-Reflex.

Here's an illustration showing both the bifurcated and Plano-Reflex style horns --
UK Columbia Horns.jpg
FROM -- percy-wilson-modern-gramophones-1929.pdf

As for the horn fitted into the Columbia 810, ten feet seems to be about right. Only Victor (and eventually the Gramophone Company) had the right to produce a folded exponential horn based one the Western Electric design, which included the taper and length of the overall sound chamber based on the numbers Western Electric (Maxfield & Harrison) came up with. All other manufacturers had to go it their own way.

OrthoFan

Thanks for the comment of the length of the 800 and 810 horn.

By the way the Orthophonic reproducer was designed by Western Electric, but Viva Tonal reproducer No.15 didn't get any patent from Western Electric. The tangential diaphragm of orthophonic reproducer has very effective compliance when it gets vibration from electric recorded 78rpm records. Unfortunately Columbia No.15 doesn't have as good compliance as orthophonice diaphragm. So as a result many owners of 800, 810 mentioned that those don't sound as good or loud as orthophonic Credenza. You can find the difference when you tap the needle sockets of those reproducers. The Orthophonic sounds clear and loud, but Viva Tonal No.15 somehow sounds less clear and seems restrained.

Watanabehi wrote: Tue Jan 28, 2025 9:28 pm
By the way the Orthophonic reproducer was designed by Western Electric, but Viva Tonal reproducer No.15 didn't get any patent from Western Electric. The tangential diaphragm of orthophonic reproducer has very effective compliance when it gets vibration from electric recorded 78rpm records. Unfortunately Columbia No.15 doesn't have as good compliance as orthophonice diaphragm. So as a result many owners of 800, 810 mentioned that those don't sound as good or loud as orthophonic Credenza. You can find the difference when you tap the needle sockets of those reproducers. The Orthophonic sounds clear and loud, but Viva Tonal No.15 somehow sounds less clear and seems restrained.

Many thanks. Yes, I knew about the differences between the reproducers, and should have mentioned it before since the Orthophonic sound box was the heart of the Western Electric design concept, and was exclusively licensed to Victor/The Gramophone Co. along with all of the other components--which, as you probably know, were designed to work together as a complete system.

I remember reading, years ago, that center cone of the diaphragms installed in the early Viva-Tonal sound boxes were "stiffened," or that a double layer of aluminum was applied, in order to make a greater area of the diaphragm plunge with the movement of the needle-bar. Of course, I can't find anything about that now.

Along this line, one sound box restorer I used to correspond with told me that in order for a Viva-Tonal sound box to function properly, the material used for the diaphragm gaskets had to be "super soft" so that the diaphragm more or less floated in its movement.

Back to horns, I'm sure you've seen this, because I posted it many times on this forum, but just in case you haven't, here's an interesting article about loudspeaker/horn design from the late 1920s covering many of the points discussed here -- OrthoFan

In the UK some collectors prefer the Columbia No.15's immediate predecessor the No.9.
Was the No.9 ever fitted to American Columbia machines? I have seen no mention of it.

epigramophone wrote: Wed Jan 29, 2025 10:44 am In the UK some collectors prefer the Columbia No.15's immediate predecessor the No.9.
Was the No.9 ever fitted to American Columbia machines? I have seen no mention of it.

I never saw a nr 9 in US machines, only the nr 15 counterpart, that looks similar to the UK design but has some differences. Both are good soundboxes, but to my taste I prefer the 15, its well-designed rubber back attachment is more flexible than the metal sheets of the nr 9.