The Talking Machine Forum — For All Antique Phonographs & Recordings

Inigo wrote: Sun Nov 14, 2021 8:14 am You could try to copy an original tinplate hmv internal horn, I mean, the snake narrow part until you reach your horn base. Maybe the shape of a101, or the longer one of a 127 would fit into your case. Anyway, these are made with plane thin sheets, simply curved to gain the increasing cross section. It seems not difficult to make from tinplate sheets, or balsa wood... You'd better calculate the cross section progress in exponential form, giving an expansion factor that matches: 1) the available length, 2) the cross sections at the tonearm base and at the horn spigot. It will be a thin conduit, placed around the motor, running by three of the case sides. You could form it using straight balsa wood boards, glued to the inner case boards using the corners of the inner case as bottom and outer sides of the horn conduit, adding only the upper and inner sides, and make Plano-reflex style corner boards at 45 degrees, instead of curved elbows, etc. It would be easy to make. And balsa wood is easy to cut, light and sound inert...?
I do my trials with another material, which is that board used by architects to make building mockups. It is a sandwich made of white cardboard and polyurethane foam in between. The total thickness is somewhat 3-4 mm or similar, and it is cheap and easy to cut.
Do you imagine what I'm proposing?

Orchorsol wrote: Sun Nov 14, 2021 9:17 am Fantastic, I hope we can hear it in action in due course!

Regarding the Orchorsol soundbox, this seller has nice soft reproduction lifebelt rubbers - I bought a couple myself some time ago: https://www.ebay.co.uk/itm/334217491402 and it may help to back off the front plate screws a little, to allow a greater gap (so long as airtightness is maintained), similar to one of the ways EMG soundboxes are tuned.

gramophone-georg wrote: Sun Nov 14, 2021 2:39 pm

Inigo wrote: Sun Nov 14, 2021 8:14 am You could try to copy an original tinplate hmv internal horn, I mean, the snake narrow part until you reach your horn base. Maybe the shape of a101, or the longer one of a 127 would fit into your case. Anyway, these are made with plane thin sheets, simply curved to gain the increasing cross section. It seems not difficult to make from tinplate sheets, or balsa wood... You'd better calculate the cross section progress in exponential form, giving an expansion factor that matches: 1) the available length, 2) the cross sections at the tonearm base and at the horn spigot. It will be a thin conduit, placed around the motor, running by three of the case sides. You could form it using straight balsa wood boards, glued to the inner case boards using the corners of the inner case as bottom and outer sides of the horn conduit, adding only the upper and inner sides, and make Plano-reflex style corner boards at 45 degrees, instead of curved elbows, etc. It would be easy to make. And balsa wood is easy to cut, light and sound inert...?
I do my trials with another material, which is that board used by architects to make building mockups. It is a sandwich made of white cardboard and polyurethane foam in between. The total thickness is somewhat 3-4 mm or similar, and it is cheap and easy to cut.
Do you imagine what I'm proposing?

Yes, and that is loosely what I attempted. Actually I am going for hyperbolic rather than exponential in the case. The bass response was fantastic but the volume was beyond anaemic likely due to the fact I was using shellac-ed cardboard with squared corners rather than bends. The reason I am thinking a round tube is due to size constraints caused by the "pyramid" style case plus the placement of the huge motor. In my calculations and drawings, the tube fits far neater and could be fabricated as a "bolt in" just like the original conduit.

I briefly toyed with the idea of installing a 2 spring Victor motor in place of the 4 spring monster, but rejected it because that's not how I work. I enjoy these sorts of "impossible" projects. My last creation for a good customer was a 1967 Mercedes 200 Diesel fintail sedan with a 1983 240D engine, a 5 speed transmission from a 1990s 190D, and a taller differential, all of which required a copious amount of fabrication to be installed AND look original to the car. Then I had to beef the suspension and brakes for the heavier engine, added power steering and a correct steel sliding roof clip, plus added period correct aircon and 1980s cruise control. This car will now climb a hill easily at 75 (121 kph) in 5th gear and runs as quiet and sure as a gas model but still looks like a 1967 200D everywhere... sort of a latter day German version of "Henry Made A Lady Out Of Lizzie".

Inigo wrote: Tue Nov 16, 2021 1:11 pm In my experience, these motors are the same, except for the fact that the Victor has a slightly longer spindle, and the turntable sits a bit raised when compared to the hmv34. I once replaced it in my 194 and I had to readjust the brake. Besides that, the hmv turntable didn't fit perfectly, so I also replaced it. Some time later I repaired the hmv motor and reverted to the original.
Nevertheless, I retained the Victor yoke semi-automatic brake, for other reasons explained herein in other posts. Briefly, this brake doesn't touch the tonearm prong until the very end, so less drag and better for the delicate bamboo needles. The original fully automatic hmv brake has a fork which is permanently attached to the tonearm prong, so permanently dragging it's movement. Lightly, but there it is. Either you disconnect it, but then, no auto-brake... I found that compromise solution the most comfortable for daily use....