The Talking Machine Forum — For All Antique Phonographs & Recordings

Thanks for posting all this information as it is really interesting. One thing I did want to ask was if it was possible to share the details of how the horn was made - ie what type of paper used (sugar paper?), the glue, and the technique if that was possible. I have seen other horn projects on you tube and their horns always seem to turn out wrinkly on the inside yet this one is as smoothe as smoothe can be both inside and out. Was any release agent used between the horn and its former? I wondered if there was a secret to achieving the perfect looking horn?

I think we can all thank Graham and Mr John Cook for the wonderful "Balmain" type gramophone photographs and descriptions.
A really interesting machine, and beautifully made. If I ever get round to finishing one that I have started, I only hope it will be half as good!

The horn is not too bad but there are wrinkles on the inner surface that do not show up in the videos. I could have spent more time trying to sand them out but I was worried about damaging the horn. Regarding the construction, I followed Peter Heath's instructions in part 2 of his excellent article. Unfortunately I cannot find any notes or photos of the process so I will outline it as I remember it.

I used lining paper from a DIY chain, they had two weights and I used the heaviest which was 0.25mm/0.0010" thick. Peter had worked out a series of arcs to make the strips of paper follow the shape of the horn so I followed these and it worked well. He recommended starting and finishing with lengthwise strips so I tried this and it does give a nice overall appearance. The paper strips were cut using hardboard patterns which I still have per the photo below showing the three curves, the inner/outer finishing strips and a spare paper cut from one of them.

I wrapped the former in Clingfilm to stop the horn sticking to it which seemed to work well enough but a mould release agent might be a better option. Perhaps Graham could advise on his experience with release agents.

Diluted PVA was used to stick the layers on. PVA gives a harder shell and during the trials I did talk to Graham about this as I wondered if it contributed to the colder sound, but it seemed similar to the fibre glass used on his wonderful horns. It would be interesting to try another one using wallpaper paste, but it is a lot of work and hopefully Alistair's horn may answer that question.

It was built up in layers in several stages and left slowly rotating to dry out and prevent sagging between sessions. The bell it is about 4.5mm thick but I made the neck 8-9mm thick as I was worried about it breaking when being handled.

Hopefully this helps but let me know if I can add anything further.

Thank you for providing so much specific information and your thoughts on the process - this is very much appreciated. Yes it will be very interesting to see whether the glue used does make a difference to the tonal sound quality of the resulting horn.

Also welcome to the board as I notice this was your very first post.

The release agent I used was "APW", a Bonda product made by Bondaglass-Voss Ltd, Beckenham, Kent which is described as a mixture of soft waxes used to release hard polyurethane foams and casting materials from GRP, wood and silicone moulds that have complicated or porous surfaces. On new moulds "APW" is applied several times, depending on porosity. It provides a soft release film and seals the pores of the mould. It is water soluable (if found necessary in extremis etc) to aid release, is applied with a cloth or sponge and has a drying time of 15-60 minutes. The advice, I think, would be to experiment with the actual materials being used---different in this case---before "going for gold" ! It is possible that the use of water might not be advisable for a paper horn in the event of a difficult release ? On the other hand, there is every reason to hope and expect that "APW" would work without water having to be employed as a last resort. In the case of the GRP bell mould where all materials were waterproof, a removable section (unbolting) was built into the design to allow a small collapse of the diameter in the event of all else failing. It has never had to be used yet---touch wood (or GRP) !

Your wish is my command Sir ! Done............

One interesting aspect of the performance comparison between Balmain and EMG Mk VIII gramophones with Wilson horns is the length of acoustic track. I have two EMG Mk VIII models here---an early example made when the firm was located in High Holborn (1924 to 1929) and a later one which came out of Grape Street (1929 to 1948). The earlier horn has a final diameter of 24 ½”, whilst the later one measures 23 ¾”. The lengths are slightly different too---earlier 48 ½”---later 49 ½”. The internal conduit has a length of 19” and tonearm right up to soundbox 16 ½”. Thus, the early auditory track totals 84” and later 85”. John’s Balmain has a length of 53.7” to the soundbox meaning that the difference is quite considerable---the Mk VIII “speaking length” is longer than the Balmain by some 31.” (787mm).

Also notable is the fact that the Mk VIII, Mk IX, Mk X and Mk Xa all had roughly similar conduit lengths. It was not until the advent of the Mk Xb and Mk Xb Oversize that the length was increased by 2”.

The early conduit is made of heavy cast iron weighing 5 ½ lbs (2.5 kg), whilst the later model employed bronze. In both cases EMG clearly understood the vital importance of “deadweight” to forestall unwanted frequencies.

Well Graham and John, I have just enjoyed viewing and listening to the three gramophone comparisons, and each one I enjoyed. The clarity was excellent in that large upstairs room.-and you were playing 1950s type 78s.
Thank you very much both of you for your time and efforts. I am sure it is appreciated by all on the forum.
Alastair.

How interesting! Mass is the first reactive impedance found by the vibrations to react against losses of sound... starting with the important reaction at the soundbox mass. Dead mass is what kills the sound leaks at first instance in the travel of sound until it reaches you. Of course, the masses needed are proportionally larger at the beginning of the chain, when the sound is very intense over a small vibrating mass, and they can be lower as the sound develops into less intense energy over a greater volume and mass of air. As in sound isolation techniques, several different values of mass are needed to retain the different frequencies of sound. An interesting matter to think about...

So mass is needed at the small end of the horn and it can be relatively lighter at the big end....?