The Talking Machine Forum — For All Antique Phonographs & Recordings

Wonderful sound from that horn: congratulations!

- Bill

I will have to admit that when you first mentioned making your own exponential horn, I had my doubts about your success. Now, all I can say is that I am completely amazed by your accomplishment... Your horn not only looks great, it sounds fantastic... Congratulations.

Now, please explain how you made your counterbalance for the reproducer, it looks quite interesting...

Congratulations Ethan on a wonderful project. It is a remarkable achievement, and you have been generous in sharing so much of it.

I am curious about how you setup to do the "sweep" you mention in the following sentence:

"The bass doesn’t go all the way down to 100 Hz.; on electrical records, there isn’t much
below about 130 Hz., and using an electric speaker in place of the soundbox, a sweep
from 10,000 to 0.1 Hz. shows a low cut-off around 156 Hz., but possibly peaks that might
be audible below that."

Thank you.

Thank you, everyone! I haven't any prior experience with large-horn talking machines, so it is very encouraging and informative to read your opinions of the horn's sound quality.

dzavracky wrote: Tue Aug 03, 2021 3:45 pm Boy Ethan that really turned out fantastic! Congrats on a successful project... I am looking forward to seeing the cabinet you make for it.

David

Thank you, David! I’ll be going back to college in a couple of weeks, so the cabinet will have to wait till winter break, or maybe next summer—either way, it will probably be something along the lines of a Mk IX cabinet; nothing very fancy, but a little nicer and easier to use than the current experimental version.

old country chemist wrote: Tue Aug 03, 2021 4:15 pm Have you tried some other reproducers?

At the moment, my only functional soundboxes are two Orthophonics and an Exhibition, but I would like to try some others at some point—possibly a Meltrope II or III if I can find one, or a No. 4. or No. 2 with aluminum diaphragm and lighter springs.

old country chemist wrote: Tue Aug 03, 2021 4:15 pm As an aside, I have never found an electric "Harmony record. I have several and they always amaze me at the volume and quality of reproduction from an acoustic record. A pity that here, in Britain, there are few to be found, sadly.

I believe the electric Harmonies were introduced in 1930 and the label was discontinued in 1932, so that would mean that they were only made for a year or two, as opposed to the five years of acoustic recordings (1925 – 1930). It is a pity that there aren't more of them on your side of the pond--it's rather odd; I would have expected them to be more common, as they're Columbia-made and the American and British Columbia companies shared some of their masters.

As emgcr noted, the bass does seem to be rather lacking considering the theoretical 100 Hz. cut-off; after adding a few more layers to the neck, the typical frequency content for a late-’20s Victor record is as pictured below—roughly equivalent peaks at 130 and193 Hz., large peak from around 300 to 1700 Hz., and high cut-off around 5000 Hz. I presume that the peaks around 8000 and 10,800 Hz. are mostly surface noise, and the peak at 50 Hz. may be in the recording, but is probably from the environment. I know that the recording levels are supposed to decrease gradually as frequency decreases, to prevent bass grooves from running into each other, but this response looks more erratic than I would have expected for the recording system, so I presume that the fault is in the reproduction.
Based on its dimensions, I’m guessing that the horn’s lower cut-off should be somewhere around the cut-off of the Mk IX or X; does anyone know roughly what their frequency responses typically are?

emgcr wrote: Tue Aug 03, 2021 7:17 pm Brilliant Ethan---many congratulations---the horn looks very good indeed. The shape would appear to be spot on and the sound is wonderful only lacking a little in the bass department at present. You are rightly concerned about mechanical strength, particularly as there is no metal swan-neck. Mk IX and X EMG horns were too weak and many quickly drooped/broke as I am sure you are well aware.

When adding wall thickness you will be killing two birds with one stone, firstly by increasing mechanical strength where it is especially needed around the bends to resist/prevent future drooping and secondly by increasing resistance to unwanted resonance by producing a very strong and stable sound conduit unable to vibrate. Both considerations are very important for top sound propagation. It is hard to tell but it would seem from the photos that you have achieved a slightly forward lean at the bell mouth which is a good thing as a vertical stance will give the impression of leaning backwards.

I wonder if you could include a very thin layer of something like Kevlar or carbon fibre at the high stress points before the final cosmetic finishing paper ?

You have cleverly positioned the whole phonograph in the corner of the room but you may find that the skilling (angled) ceiling might produce some strange sound reflections. It might be worth experimenting in a fully right-angled corner if you have one available ?

Superb work.

Thank you! I have indeed heard of the infamous self-destructing Mk IX and X horns—in fact, a wooden support has been part of my plan since the beginning; in its final form, something like the metal strip in the Mk X, but possibly a little longer in relation to the neck. Would Kevlar or carbon fiber be primarily rigid or tear-resistant? From pictures that I’ve seen, it looks as though the weight of Mk IX/X horn mouth usually bent the neck down, flattening it vertically until the sides cracked, in which case something stiff enough to prevent the initial sagging might be more effective than something to prevent the splitting.

Odd reflections are probably inevitable in my room; it has an angled ceiling on two opposing walls, and the only place with the standard right-angle ceiling is a five-by-six-foot niche with a window in the back on one wall, there probably isn’t a truly ideal place for such a large horn—still, trying different arrangements would be a good idea; small rooms can have a significant impact on the sound quality of large horns.

Curt A wrote: Thu Aug 05, 2021 9:32 pm I will have to admit that when you first mentioned making your own exponential horn, I had my doubts about your success. Now, all I can say is that I am completely amazed by your accomplishment... Your horn not only looks great, it sounds fantastic... Congratulations.

Now, please explain how you made your counterbalance for the reproducer, it looks quite interesting...

Thanks, Curt! I can't say that I was completely convinced that it would work out, either, especially as I didn't really have much experience designing or making horns before. The counterweight is made from Legos, with a couple of steel marbles in the two rocks at the end—it isn’t scientifically designed; I just adjusted the position of the weights until I reached the lowest weight at which the needle can still track without rattling around in the groove or jumping out from warpage or off-center pressing. Reducing the weight of the soundbox on the record to around 65 grams worked fairly well on the Alhambra and seems to work on the homemade gramophone as well, but I’ve read that larger horns need more tracking weight, so I’ll probably experiment more.

TN Allen wrote: Sat Aug 07, 2021 2:10 pm Congratulations Ethan on a wonderful project. It is a remarkable achievement, and you have been generous in sharing so much of it.

I am curious about how you setup to do the "sweep" you mention in the following sentence:

"The bass doesn’t go all the way down to 100 Hz.; on electrical records, there isn’t much
below about 130 Hz., and using an electric speaker in place of the soundbox, a sweep
from 10,000 to 0.1 Hz. shows a low cut-off around 156 Hz., but possibly peaks that might
be audible below that."

Thank you.

Thank you!--And good luck with your horn project; it sounds very interesting!

For the sweep, I adapted a speaker from a pair of headphones by removing the plastic grille, adding a metal enclosure, and fastening the metal insert from a petrified Orthophonic soundbox isolator; then I just plugged it into a cell phone, used an online sweep generator to produce the sound, and recorded it with the Audacity audio workstation software on my computer. It isn’t a perfect test—a real horn driver, or better yet, the constant tone/gliding tone records made by Victor, HMV, and Decca would be better, especially as they would test the response of the whole instrument, instead of just the horn—but it at least gives a general idea of the frequency response.

All it is very interesting, thanks for sharing it.
Although not proper for an emg style horn, I would suggest to consider making a horn crane to help supporting the huge bell, freeing the neck from that large stress. Something in the lines of the Joe Busam's Ediphonic horn, which is a huge exponential horn attached to a homemade phonograph made from an Amberola guts. The maker's name is Thomas E. Kimble.. (?)
That horn is very interesting, and sounds wonderful. Kind of an emg-phonograph... Notice how the horn is supported on a cord hanging from twin cranes at both sides, supported in turn by the machine case. A similar principle could be applied to your machine. If you make the case heavy enough, it could well support the cranes and the enormous horn.
Watch it here. I'm amazed by this machine
https://youtu.be/jhLjcfswHb0

"Thank you!--And good luck with your horn project; it sounds very interesting!"

A large exponential horn does interest me, however, I may not build it as I already have far too many unfinished projects that may well outlive me.

"For the sweep, I adapted a speaker from a pair of headphones by removing the plastic grille, adding a metal enclosure, and fastening the metal insert from a petrified Orthophonic soundbox isolator; then I just plugged it into a cell phone, used an online sweep generator to produce the sound, and recorded it with the Audacity audio workstation software on my computer. It isn’t a perfect test—a real horn driver, or better yet, the constant tone/gliding tone records made by Victor, HMV, and Decca would be better, especially as they would test the response of the whole instrument, instead of just the horn—but it at least gives a general idea of the frequency response."

That is a very clever and resourceful solution!

Testing the reproducer in place playing a recording similar to the Holm Impulse sweep would be great, but finding a source to make it accurately is probably all but impossible.

Alternatively, I've wondered about a mechanical link between a small full range speaker and the needle, which might carefully be played to vibrate the needle. Properly positioned, the vibrations might simulate the needle vibration in a record. A wire looped and glued at the intersection of the surround and cone or dome surface might be a start. The other end of the wire would then connect with and vibrate the needle.

You are already accomplished at thinking outside the box... who would have thought of making a counterbalance out of Legos?

That being said, I think you will find a good solution to the horn support question... Inigo's idea of a double Cygnet horn crane seems to be a viable idea, since it supports the weight without taking away from the aesthetics of your horn design by adding additional built in support.

Maybe you could make a metal ring that slides over the outside of the horn, past the goose neck and near the mouth that would have two metal rings to attach the cranes with a spring suspension (like an Edison Cygnet crane), instead of the cabling like used in the video... I'm sure you will figure it out.

Good luck on the rest of the project.

Curt

The Ediphonic certainly does sound good! A crane might work for my horn; the current cabinet is heavy enough to hold it up, and the non-experimental cabinet will be slightly larger, made from ¾” plywood instead of ½”, and lidded, so it should be heavy enough to hold the horn and a crane. If the wood keel doesn’t turn out well, I may try one; in addition to taking stress off the neck, it would probably take stress off the glued joints between the horn and the wood mounting rings.

TN Allen wrote: Sun Aug 08, 2021 8:58 am Testing the reproducer in place playing a recording similar to the Holm Impulse sweep would be great, but finding a source to make it accurately is probably all but impossible.

Alternatively, I've wondered about a mechanical link between a small full range speaker and the needle, which might carefully be played to vibrate the needle. Properly positioned, the vibrations might simulate the needle vibration in a record. A wire looped and glued at the intersection of the surround and cone or dome surface might be a start. The other end of the wire would then connect with and vibrate the needle.

There definitely are records from the ’20s and ’30s that were designed for frequency response testing, but I don’t imagine they’re that common. I did some brief searching on eBay, and the only one that turned up was in England, and the shipping cost was very prohibitive.

Using a speaker to drive the soundbox might work; it reminds me of a device that (I believe) was sold in the ’20s—it used the electrical signal from a radio to vibrate the needle in the soundbox, so one could listen to the radio through a phonograph’s horn.

Curt A wrote: Sun Aug 08, 2021 7:56 pm You are already accomplished at thinking outside the box... who would have thought of making a counterbalance out of Legos?

Thank you! Legos have been one of my major interests for years—in fact, when I first started to take an interest in acoustic talking machines, I tried making a tinfoil phonograph from them (it didn’t work—Legos are too inherently flexible, so I couldn’t get the needle to follow the groove it made in the foil), and made a sort-of-working hand-driven disc machine with a cardboard horn and cobbled-together soundbox.

I did some more not-very-scientific frequency response tests over the past few days, and after adding three layers overlapped halfway (six sheets) to the horn and one layer overlapped two-thirds (three sheets) to the internal conduit, there seems to be a slight improvement in bass; measuring the frequency content of the same record, the 130 Hz. peak has dropped to 125 Hz. and increased in amplitude—hopefully a sign that the increasing thickness is preventing low frequencies from passing through the horn walls. I’ll be adding more layers over the next few days, so it will be interesting to see—and, more importantly, hear—whether the trend continues.
Here are a few videos of the gramophone playing in its current state:

https://www.youtube.com/watch?v=8iXCRqzzazk

“Humoreske—Op. 101, No. 7”—The Hastings Municipal Orchestra.

https://www.youtube.com/watch?v=YKSoPkEHqPQ

“We’re the Sunday Drivers”—Billy Murray’s Trio.

https://www.youtube.com/watch?v=ndzY0kKpVfQ

“The Lamplighters”—A “Medley of Irish Reels” by Joseph Samuels and Frank Banta.

https://www.youtube.com/watch?v=7lcSOOEFIC0

“ ‘Waiting for the Robert E. Lee’ Medley Turkey Trot”—Victor Military Band.

Ethan,

Your grasp of the physics is laudable. You seem to have researched it thoroughly. I am curious about the following (below) from one of your earlier posts. I'd like to read more about this method for determining cutoff frequency in order to understand the physics better, and would appreciate knowing where to locate the material describing it because it may also relate to designing audio waveguides, which is another subject that interests me.

Also, good luck returning to college. If it is for engineering, I suspect you will be a remarkable engineer.

"Interestingly, one of the cut-off frequency-determining methods I’ve found is that the mouth diameter needs to be roughly equal to the wavelength of the lowest frequencies to be passed through the horn; my horn has a 27” diameter mouth, which means roughly an 85” perimeter—and that corresponds approximately to the wavelength of a 160 Hz. tone, which is roughly where the measured cut-off is when using the electric speaker."

This rule of the horn mouth having the perimeter of the longest wave desired to be transmitted (the design cutoff frequency of the horn) has been modified by others, maybe same Percy Wilson, telling that an acceptable approach is this same measure divided by 1.25.
Another advice from PW is that the angle of the horn to its axis at the mouth should not be lower than 41 degrees.
These are experimental rules that help reducing the size of the horn for a desired cutoff frequency.
In all, the one that saves most space is the theory of the solid angle of sound distribution, which says that once the theoretical horn has been designed, it's cross section area along the whole axis can be divided by the solid angle of sound radiation ratio to the complete solid angle of a sound source in the space (the complete spherical wavefront emerging in all directions from a sound source. Thus, if your horn is placed so its mouth radiates only to an hemispheric space (case of the horn mouth being placed emerging in an infinite wall, baffle, so it only radiates sound to one side of the wall) the cross sections can be divided by two. If it is placed at the corner of a wall and floor or ceiling, so it radiates only to a quarter space, can be divided by four. And the most interesting one: if the horn is placed at the corner of two walls and the ceiling, it will radiate only to an eighth of the complete sphere, so its cross section can be divided by eight.
This said, your horn is placed in this last case, so its cross section could be an eighth part of the theoretical area designed for a given cutoff frequency. Or reading it in reverse way, your horn placed in such a corner, produces the same effect of a full size horn with cross section areas eighth times greater. This means that the longest wavelength you may hear is indeed the square root of eighth (2.83) times the wavelength of your horn placed in the full space all around. So if your mouth perimeter is 85", placed in such corner it would sound like a mouth 2.83 times larger, 240" perimeter. So the lowest sound you'd hear would be a six meter wavelength, it is, 56Hz. So maybe the peak you registered at 50Hz is not external to the horn, but the true lowest sound transmitted by it!!
What I don't know is if the mouth perimeter rule and the 41 degrees rule apply to the original theoretical horn (full area) or to the reduced one...