@ OrthoFan, as it happens, I was already considering making another post specifically about the differences in Orthophonic tone-arms, partly to help me decide which tone-arm would work best for my project, and partly just as a useful resource for anyone interested in variations between models—I only have two tone-arms to contribute, myself, but others might be able to share photos and dimensions of their tone-arms, as well.
Orchosol wrote:I believe you won't get all the sonic benefit of a large and well designed horn system that way.
Unfortunately, that’s just about the same conclusion that I’ve been coming to—I think that I’ll just have to make the best design that I reasonably can, given my limited space and designing experience, and then experiment with different locations in my room, needle types, and probably also materials to stuff in the horn mouth if all else fails. (Also, while I’m on the subject of loudness, do you happen to know the average decibel level, for a given needle, type of music and recording, and distance from the horn mouth, of the external-horned EMGs? I have read various descriptions of the sound and volume, but very few actual measurements.)
Orchosol wrote:A lot of us EMG enthusiasts find that they give of their very best when they're driven hard and loud!
This is something that I’ve heard multiple times before on this forum, but have never quite understood, as, from what I have read, exponential horns should require a quieter input than non-scientifically designed horns in order to produce the same output volume—Does it have something to do with the way in which louder sounds interact with the room?
Orchosol wrote:By the way, I might be wrong here but isn't "straight-horned Orthophonic" a contradiction in terms?
I don’t believe that “straight-horned Orthophonic” is contradictory; I’ve gathered that “Orthophonic” was just a marketing term used to describe the whole system of electrical recording and matched-impedance reproduction—The first four models in the Orthophonic range were the Consolette, Colony, Granada, and Credenza, of which the first three all had the same straight horn and only the Credenza had a folded horn, so it seems to me as though the straight horn started out as the standard “Orthophonic horn,” with the larger, folded horn only used in the top-of-the line model, but then Victor began introducing smaller folded horns even in tabletop Victrolas, so the straight horn became the economy version.
I tried finding “Armchair Phonatics,” but I only found one result, which only got as far as plotting out the horn’s radii on a piece of paper—it looks as though the plan may be for a Wilson horn, given the 48” length and 24” diameter mouth; but at any rate, the cut-off frequency appears to be about 166 Hz., which is higher than I would like, although I suspect that, because I use extra-soft-tone needles, a good treble response is more important than a good bass response for me.
I think, however, that I may have found a solution to the problem of making a mould/former; I was talking about my designs with my father over the weekend, trying to think of a way to make the former for the curved section of the horn, and he found a description of how to make a former at a site called Inlow Sound—the method won’t work for a curved horn, but it looks as though it could work very well indeed for a straight horn, so I should be able to use it either for most of the Mark VIII-like horn or for the mouth section of the Mark X-like horn.
If I use the Inlow Sound method for the straight section, will fabric-and-sawdust (or sand) work well enough for the former for the narrow-diameter curved section? I’m fairly good at simple sewing—I made myself a frock coat from an adapted morning coat pattern a few years ago, although I wouldn’t ask anyone other than myself to wear it in public—so I ought to be able to get the shape right; the two main problems that I can see are lack of rigidity, because the filling will probably be able to shift around a little, and removal of the former—Might it work to coat it carefully with plastic wrap, then, when the horn is dry, empty the filler and peel out the fabric and plastic wrap? (I might be able to whip up a sketch, if anyone is having trouble picturing this.)
To join the straight section to the curved section in the Mark VIII-type horn, would it work to place the finished curved part in place on the end of the former, then build up paper layers over it as the straight section is being made? (See my sketch, below.)
For the joint between the horn and the internal conduit, should a socket made from ¼” aluminum tubing be strong enough to support the weight of either a roughly four-foot-long horn or a Mark X-like horn with a plywood “keel” along the inside of the large curve? I’m thinking that the throat of the horn will have a piece of tubing built into it, such that an inch or two protrudes and can slide into another tube at the end of the internal conduit, as shown on a Mark VIII-type horn in the lower left pane in my sketch.
Should I be planning on making some kind of external support for the Mark VIII-like horn, to prevent the horn from breaking under its own weight or unbalancing the cabinet? To keep the cost and complexity fairly low, I’m planning on making a cabinet similar to the sort used on the later EMGs, but with the horn coming up towards one side, such that cabinet can be placed against a wall while still allowing the horn to be swung clear of the lid; but it seems as though the horn might unbalance it when swung to the side.
Also, would it make it any easier to read my posts if, instead of saying “Mark VIII-like” or “Mark X-type,” I use my own horn design designation and attached a couple of scans from my design notebook, showing sketches of the two designs with their designations? (The Mark X-like horn, for example, is Type B, No. 16, or simply “B-16,” in my notebook, which might be easier to read.) It occurs to me that my posts are a trifle—er—lengthy, and might be easier to read with a simple designation and reference sketch, instead of a comparison to the nearest EMG horn.
