An Introduction and Some Questions about Exponential Horns
Posted: Fri Jun 19, 2020 10:53 am
Hello,
As the topic title suggests, this is my first post on the forum, so I will begin with a brief (-ish) introduction—
I first became interested in phonographs about two years ago, when my tenth-grade U.S. history teacher shared an on-line article about music during the Great War, with links to some recordings of contemporary Victor records—I rather liked some of the music, and part-way through eleventh grade, I bought a 1915 VV-VIII, so that I could listen to original ragtime and ragtime-esque music (roughly pre-1920) as it was originally meant to be heard—But, along with the VV-VIII came a few acoustic Paul Whiteman records and one Orthophonic fox-trot from 1930 . . . and I started to become more interested in dance music from the ’20s as well . . . but I couldn’t adjust the VV-VIII’s soundbox to my satisfaction . . . So I began trying to find information about horn design . . . and learned about the Orthophonics and E.M.G.s . . . and bought a VV2-55, mostly for its relatively stable soundbox . . . then started buying more Orthophonic dance music . . . then made a cardboard 150-Hz. modified exponential horn for use with the VV2-55’s tone-arm and soundbox . . . then bought a Victrola Alhambra, as the brighter sound of the straight-horned Orthophonics seemed preferable to the somewhat muffled sound of the folded-horn models . . . but it doesn’t have nearly the bass or treble response of the cardboard horn . . . so I decided that, if I wanted a phonograph with reasonably flat and wide frequency response, I should make something along the lines of an E.M.G., using an Orthophonic soundbox and tone-arm (a real E.M.G. gramophone would be far outside my price range).
So far, I have come up with numerous horn designs, ranging from a 90-Hz. wooden folded exponential horn to a 150-Hz. straight tractrix horn—But there remains a major problem before I can choose a design and start construction: The only large exponential-horned phonograph that I have heard in person is the Credenza in Debence Antique Music World, in Franklin, PA, which, as I recall, rattled, although whether the origin of the rattle was a dirty record, a worn record, a worn needle, an out-of-condition soundbox, or an unsealed horn, is a mystery. I have read the relevant sections of Modern Gramophones and Electrical Reproducers, a couple of more recent technical articles that I only half-understood, and numerous discussions about horn design on this forum; but even so, I have mostly only read about, not heard, the different sounds of various sizes and types of exponential-horn phonographs—So, I decided that it was about time to join the forum and ask some questions directly, instead of just reading other somewhat-relevant discussions.
First, I will say that I am aiming for the best sound possible, given my means and space available (which is rather lofty goal to reach for); but, at the minimum, my final design should sound at least as good as a Credenza, the best-sounding phonograph that I can reasonably hope to afford—otherwise, I’ll probably just start saving my allowance and looking on Ebay and Craigslist.
My first few questions are (or at least I hope are) fairly simple—
Of the E.M.G Marks VIII through Xb Oversize, which machine is quietest, for a given record and needle? My room is small—about twelve feet by fourteen, with a roughly six by four-and-a-half-foot alcove—so quieter is better.
How does a Mark VIII compare to a Credenza, in terms of both frequency response and “that magical E.M.G. quality?” One of my more reasonable designs is for a roughly-133-Hz. straight horn, which has a mouth angle of about 42° and mouth diameter of about 28”, and which I presume would sound similar to a Mark VIII, owing to the similar shape and size.
And now for the trickier questions—
Does anyone have any suggestions for how to make a mould? I have gathered that E.M.G. used wood disks, stacked, cut, and sanded to the correct shape, but this sounds rather complicated; and I have read of making a fabric mould, stuffed with sawdust, but this seems as though it would be hard to use for anything but a straight horn, and even then prone to irregularities in the contour of the horn.
What sorts of paper would work well for the horn material? My current plan is to use torn sheets of packing paper, for no other reason than that it seems reasonably cheap and easy to find.
What kind of glue should be used? I read of someone on this forum using “white glue,” and wondered whether something easily obtainable, such as Elmer’s, would work—Also, this person diluted the glue; does anyone have any idea how much glue should be used for a given amount of water?
Should each layer of paper be allowed to dry before adding another (which might take rather a long time), or should new layers be added before the older ones have dried (which might prevent the inner layers from drying)?
And now for the trickiest—in other words, technical—questions—
Is an Orthophinic soundbox, properly rebuilt, suitable for use with a non-Orthophonic horn, such as those used by E.M.G.; or for use with a horn larger than the Credenza’s? I have read several posts on this forum that indicate that the Orthophinc soundboxes are designed specifically for a certain size of folded Orthophonic horn, but I have been unable to find any scientific articles or analyses to support these claims.
Does anyone know, from first-hand experience, whether constant-bore sections at small diameters—say, under two inches—substantially affect the frequency response of a horn? Modern Gramophones says that they should not, but some forum members—I forget which—have said that maintaining the exponential expansion throughout the entire length of the horn is critical, except where the taper is so slight that a conical section is practically the same shape.
Is there a scientific or mathematical relationship between the diameter of a horn, the radius around which it is bent, and the frequencies that will be filtered out? Modern Gramophones says that tight bends should be kept at diameters below about two inches (indicating that loose bends can occur safely at larger diameters), but does not specify when a bend is tight and when it is not.
Were E.M.G. gramophones designed specifically to face straight out from corners of rooms—that is, 45° from each wall? E.M.G. horn mouths have always seemed to have too small a final angle, to me; but while researching horn design, I came across an article that—I believe—suggests that, for a given rate of taper (cut-off frequency), a horn designed to play out of a corner not only can, but should, have a smaller mouth than the same horn as designed to play perpendicular to a wall, if a smooth frequency response is desired. (I will be posting another thread specifically about this fairly soon, as I am not at all sure that I interpreted the article correctly, but this post is already a trifle lengthy to ask here.)
Should anyone happen to have any useful advice or information, I thank you for your time, and for your patience in wading through my post—I have been researching and trying to design horns for some time now, so I have several months’ worth of questions.
- Ethan
As the topic title suggests, this is my first post on the forum, so I will begin with a brief (-ish) introduction—
I first became interested in phonographs about two years ago, when my tenth-grade U.S. history teacher shared an on-line article about music during the Great War, with links to some recordings of contemporary Victor records—I rather liked some of the music, and part-way through eleventh grade, I bought a 1915 VV-VIII, so that I could listen to original ragtime and ragtime-esque music (roughly pre-1920) as it was originally meant to be heard—But, along with the VV-VIII came a few acoustic Paul Whiteman records and one Orthophonic fox-trot from 1930 . . . and I started to become more interested in dance music from the ’20s as well . . . but I couldn’t adjust the VV-VIII’s soundbox to my satisfaction . . . So I began trying to find information about horn design . . . and learned about the Orthophonics and E.M.G.s . . . and bought a VV2-55, mostly for its relatively stable soundbox . . . then started buying more Orthophonic dance music . . . then made a cardboard 150-Hz. modified exponential horn for use with the VV2-55’s tone-arm and soundbox . . . then bought a Victrola Alhambra, as the brighter sound of the straight-horned Orthophonics seemed preferable to the somewhat muffled sound of the folded-horn models . . . but it doesn’t have nearly the bass or treble response of the cardboard horn . . . so I decided that, if I wanted a phonograph with reasonably flat and wide frequency response, I should make something along the lines of an E.M.G., using an Orthophonic soundbox and tone-arm (a real E.M.G. gramophone would be far outside my price range).
So far, I have come up with numerous horn designs, ranging from a 90-Hz. wooden folded exponential horn to a 150-Hz. straight tractrix horn—But there remains a major problem before I can choose a design and start construction: The only large exponential-horned phonograph that I have heard in person is the Credenza in Debence Antique Music World, in Franklin, PA, which, as I recall, rattled, although whether the origin of the rattle was a dirty record, a worn record, a worn needle, an out-of-condition soundbox, or an unsealed horn, is a mystery. I have read the relevant sections of Modern Gramophones and Electrical Reproducers, a couple of more recent technical articles that I only half-understood, and numerous discussions about horn design on this forum; but even so, I have mostly only read about, not heard, the different sounds of various sizes and types of exponential-horn phonographs—So, I decided that it was about time to join the forum and ask some questions directly, instead of just reading other somewhat-relevant discussions.
First, I will say that I am aiming for the best sound possible, given my means and space available (which is rather lofty goal to reach for); but, at the minimum, my final design should sound at least as good as a Credenza, the best-sounding phonograph that I can reasonably hope to afford—otherwise, I’ll probably just start saving my allowance and looking on Ebay and Craigslist.
My first few questions are (or at least I hope are) fairly simple—
Of the E.M.G Marks VIII through Xb Oversize, which machine is quietest, for a given record and needle? My room is small—about twelve feet by fourteen, with a roughly six by four-and-a-half-foot alcove—so quieter is better.
How does a Mark VIII compare to a Credenza, in terms of both frequency response and “that magical E.M.G. quality?” One of my more reasonable designs is for a roughly-133-Hz. straight horn, which has a mouth angle of about 42° and mouth diameter of about 28”, and which I presume would sound similar to a Mark VIII, owing to the similar shape and size.
And now for the trickier questions—
Does anyone have any suggestions for how to make a mould? I have gathered that E.M.G. used wood disks, stacked, cut, and sanded to the correct shape, but this sounds rather complicated; and I have read of making a fabric mould, stuffed with sawdust, but this seems as though it would be hard to use for anything but a straight horn, and even then prone to irregularities in the contour of the horn.
What sorts of paper would work well for the horn material? My current plan is to use torn sheets of packing paper, for no other reason than that it seems reasonably cheap and easy to find.
What kind of glue should be used? I read of someone on this forum using “white glue,” and wondered whether something easily obtainable, such as Elmer’s, would work—Also, this person diluted the glue; does anyone have any idea how much glue should be used for a given amount of water?
Should each layer of paper be allowed to dry before adding another (which might take rather a long time), or should new layers be added before the older ones have dried (which might prevent the inner layers from drying)?
And now for the trickiest—in other words, technical—questions—
Is an Orthophinic soundbox, properly rebuilt, suitable for use with a non-Orthophonic horn, such as those used by E.M.G.; or for use with a horn larger than the Credenza’s? I have read several posts on this forum that indicate that the Orthophinc soundboxes are designed specifically for a certain size of folded Orthophonic horn, but I have been unable to find any scientific articles or analyses to support these claims.
Does anyone know, from first-hand experience, whether constant-bore sections at small diameters—say, under two inches—substantially affect the frequency response of a horn? Modern Gramophones says that they should not, but some forum members—I forget which—have said that maintaining the exponential expansion throughout the entire length of the horn is critical, except where the taper is so slight that a conical section is practically the same shape.
Is there a scientific or mathematical relationship between the diameter of a horn, the radius around which it is bent, and the frequencies that will be filtered out? Modern Gramophones says that tight bends should be kept at diameters below about two inches (indicating that loose bends can occur safely at larger diameters), but does not specify when a bend is tight and when it is not.
Were E.M.G. gramophones designed specifically to face straight out from corners of rooms—that is, 45° from each wall? E.M.G. horn mouths have always seemed to have too small a final angle, to me; but while researching horn design, I came across an article that—I believe—suggests that, for a given rate of taper (cut-off frequency), a horn designed to play out of a corner not only can, but should, have a smaller mouth than the same horn as designed to play perpendicular to a wall, if a smooth frequency response is desired. (I will be posting another thread specifically about this fairly soon, as I am not at all sure that I interpreted the article correctly, but this post is already a trifle lengthy to ask here.)
Should anyone happen to have any useful advice or information, I thank you for your time, and for your patience in wading through my post—I have been researching and trying to design horns for some time now, so I have several months’ worth of questions.
- Ethan
as with most things you can’t always expect the first one to turn out perfect. But hopefully I can make the first one really good