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 Post subject: Re: PAPER HORN
PostPosted: Sat Oct 17, 2020 7:36 pm 
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Victor II
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What a great way to spend a day. The sight of all three gramophones together is just so surreal.
I'm well impressed with the Balmain design but do think the others outperform it. I'm sure there is scope for further experiments, perhaps with a more compliant fitting between the soundbox and horn.


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 Post subject: Re: PAPER HORN
PostPosted: Sat Oct 17, 2020 8:41 pm 
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Victor Jr
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What a wonderful day! I wish I had been there. I am wondering about the level of reflection that the red paint may be causing on the Balmain-style horn. It sounds very good indeed, but I suspect a tad bright because of the reflections. Might be a fun prospect to try a matte finish on the inside and re-test. Eternally fascinating, this hobby of ours...



emgcr wrote:
John Cook, the skilled maker of the red-horned Balmain-design Wilson horn gramophone visited my home on Friday and we spent many enjoyable hours comparing the audio output of three external-horn gramophones---Balmain, EMG Mk VIII and EMG Xb Oversize. It occurred to us that nobody has yet ever had the public opportunity of hearing such comparisons as, so far as is known, no original Balmain gramophone exists.

During the course of this thread there have been a few doubts expressed as to whether the Balmain gramophone is really a practical proposition and would work in a satisfactory fashion. I can confirm that it performs brilliantly in all required respects---plays perfectly with absolutely no detectable increased record wear---but does, of course, need to be set up very carefully. As mentioned previously, it is vital that the track/carriage is absolutely level in both planes. It is also extremely important that the construction dimensions result in the correct needle pressure and that the rolling track friction is as low as possible. In this case John has allowed generous tolerances in order to minimise friction and allow for irregularities in records etc. Different soundboxes were tested which resulted in slightly different lateral needle positions, thus adjustments (allowed for in the design) had to be made each time the soundbox type was changed so as to ensure correct tracking to the centre of the motor spindle. Exhibition, HMV and EMG soundboxes were assessed with the latter proving the most satisfactory.

For those wishing to make their own, John has the following initial recommendations and is also more than happy to answer questions by email/telephone etc upon request. There is much to think about before embarking but his first recommendation is to decide upon the length of (Wilson-type) horn. This decision is not easy and reference should probably be made to Peter Heath’s excellent PDF attachments earlier in this thread. It would then be wise to make the bare horn and soundbox attachment before anything else so that weight and point-of-balance can be exactly determined. John’s horn weighs 3.2 kg (7.05 lbs). Possessing this definite item, calculations can then be made in respect of track length and horn pivot point. After this, he suggests making a cheap softwood construction to prove the design before going to the trouble of finely-finished hardwood.

John has used an HMV 32 double-spring motor and the case contains a heavy cast-iron weight to act as a counterbalance. Were he to do the job again, he would construct the case to allow removal of the counterweight without having to lift the motor board.

Here are the performance videos :

https://www.youtube.com/watch?v=owX7Pnqm-Nw Balmain-design gramophone in action---close up.

https://www.youtube.com/watch?v=z16o39aT_UQ Balmain-design gramophone comparison demonstration. Steel needle. BALMAIN.

https://www.youtube.com/watch?v=nYbKo9ufA4w Balmain-design gramophone comparison demonstration. Steel needle. EMG Mk VIII.

https://www.youtube.com/watch?v=OLfxyVOWV_8 Balmain-design gramophone comparison demonstration. Steel needle. EMG Xb Oversize.


https://www.youtube.com/watch?v=8E16t5Ne4JI Balmain-design gramophone comparison demonstration. Thorn needle. BALMAIN.

https://www.youtube.com/watch?v=JRyUHCo01ok Balmain-design gramophone comparison demonstration. Thorn needle. EMG Mk VIII.

https://www.youtube.com/watch?v=HuJ8uZq7PEs Balmain-design gramophone comparison demonstration. Thorn needle. EMG Xb Oversize.

Followed by detailed photos :


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 Post subject: Re: PAPER HORN
PostPosted: Sun Oct 18, 2020 5:36 am 
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Victor III
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chunnybh wrote:
I'm sure there is scope for further experiments, perhaps with a more compliant fitting between the soundbox and horn.


Interesting comment Chunny. We did try a "lifebelt" but the particular one we used caused pitch flutter. It may well have been too soft and, indeed, the situation did improve when we surrounded it with a jubilee clip. As you say, more experimentation to be done.


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 Post subject: Re: PAPER HORN
PostPosted: Sun Oct 18, 2020 6:03 am 
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Victor III
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BassetHoundTrio wrote:
I am wondering about the level of reflection that the red paint may be causing on the Balmain-style horn. It sounds very good indeed, but I suspect a tad bright because of the reflections. Might be a fun prospect to try a matte finish on the inside and re-test.


Excellent point Spencer and you are right---the inside surface of the horn has a slightly satin finish. The horn structure is layered up with PVA which perhaps produces a harder, more resonant, surface when compared to the "softer" construction of the paper Wilson horn which employed something like wall-paper paste. Having said that, I did find on my own GRP horn bells that a physically hard surface was not, of itself, a problem---the important thing seems to be to encase the evolving sound waves in a completely mechanically stable environment. Wall-thickness is relevant for this reason.

A perhaps more important point relates to the length of the horn. Although John's horn is longer than the original Wilson examples, the total acoustic track from soundbox to bell mouth is longer in the case of the EMG Mk VIII having allowed for the internal conduit and tonearm. I shall take measurements to quantify this difference exactly. From memory and in very rough terms I think we are talking of approximately 24 inches---maybe more.


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 Post subject: Re: PAPER HORN
PostPosted: Sun Oct 18, 2020 6:24 am 
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Victor O
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Location: Near Durham, Northeast of England
What a simply wonderful post! Much joy is to be had looking and listening to these beasts of musical majesty!

Superb!!!!!
"I might of come across a darned sight cleverer if I'd kept my mouth shut....."


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 Post subject: Re: PAPER HORN
PostPosted: Sun Oct 18, 2020 12:04 pm 
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Victor III
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John is awaiting approval to be able to comment on this forum and, in the meantime, has asked me to post the following :

I must thank Graham for hosting this most interesting day.

The machine is basically a copy of Peter Heath's original machine detailed in the articles published in the Hillandale News in 2000 and re-posted on this thread recently. I saw Peter demonstrate his machine at the Northampton Phonofair and was amazed by its performance, not having heard anything beyond an HMV 157 at the time, so I resolved to build a copy. Peter's research and carefully thought out design made building this copy relatively straightforward. The railway wheels were one deviation as I did not have the facilities to machine the carriage to Peter's design. Peter had designed his machine to take an HMV 5B soundbox and I followed the same path as they were readily available. I have sent a message to Peter as it would be very interesting to get his thoughts and see if he developed the machine further. I used the machine for a while but found it impractical for regular use, the main concern is keeping it perfectly level or it can skip grooves. It also has no lid so the needle noise can be distracting. On Friday we kept the lids open on the other machines for comparison.

The choice of records for the videos was difficult and two fairly extreme examples were chosen which seemed to work for comparison purposes. FDR Jones was a fairly worn copy that I usually use to set the machine up, it has some wear to the first few grooves that can skip so we used a steel needle. Mr Sandman and Frenesi were clean copies and worked with a correctly sharpened thorn needle.

We tried a number of soundboxes and found the EMG 2 spring had a clear edge over the HMV 5B and EMG 4 spring on this machine. This soundbox was then used on all the machines and records filmed, eliminating one major variable. I am not aware if there are any records of the original soundboxes used on these machines. As the original probably had a mica diaphragm, an Exhibition was tried out of interest but gave poor results, the HMV No 4 was much better but still behind the EMG.

Graham tried a 12" record---“O del mio amato ben”---Donaudy---Gigli. This played successfully with a thorn needle but showed up an unacceptable wow and flutter in the HMV 32 motor so we did not film it. I must say that hearing this same record on his Xb oversize really showed how wonderful these machines can be and was the finest combination of the day :

https://www.youtube.com/watch?v=MsbMVQ8vu2s

The comparison with the EMG Mk VIII was perhaps the most interesting aspect for me. As you can see from the photos the main body of the horns are pretty close with a 24" mouth and very similar profile. The difference in performance in the room was noticeable, with the Mk VIII having greater clarity, base response and a certain warmth of tone, lacking in the Balmain. I found this slightly surprising as the conventional wisdom seemed to be that a perfectly straight horn with no bends should be the aim. Measuring the Mk VIII internal conduit and tone arm, these made the total sound path about 30" longer than the Balmain but also added six bends and a non-exponential section. This seems to confirm previous experiments that bends and parallel sections in this early part of the path have no detectable negative impact. Another problem may be that as the horn was designed for the larger bore of the HMV 5B, there is a sudden step in diameter when fitting a smaller bore soundbox such as the EMG.

We did discuss the finish on the horn as a possible reason for the rather bright performance, but it seemed comparable to the internal fibreglass finish on one of Graham's fine oversize horns. It is certainly something to experiment with.

I see from the earlier thread that Chunny has an original Balmain horn. It would be interesting to compare the dimensions with Peter's design and also know how much it weighs. I could not see any attachment points to suspend the horn in the photos, but they may have been out of shot.

The second point raised was that it had a lifebelt fitted. We had to use a crude rubber tube to fit the Exhibition and HMV No4 soundboxes and this caused an oscillation to build up between the soundbox and the horn so we fitted a jubilee clip to increase the rigidity of the joint. This is also certainly worth further investigation.



Last edited by emgcr on Sun Oct 18, 2020 12:31 pm, edited 3 times in total.

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 Post subject: Re: PAPER HORN
PostPosted: Sun Oct 18, 2020 12:25 pm 
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Victor Jr
Joined: Mon Nov 11, 2019 3:14 pm
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could those youtube videos be made public?


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 Post subject: Re: PAPER HORN
PostPosted: Sun Oct 18, 2020 12:32 pm 
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Victor III
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I don't see why not---all of them ? They are currently "Unlisted" which means that anyone can forward the link to anyone else to view.


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 Post subject: Re: PAPER HORN
PostPosted: Sun Oct 18, 2020 4:23 pm 
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Victor III
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More detail from John..................

Please find attached a couple of photos of the horn former as requested. It is sat up in the garage roof so it is not easy to get a clear photo. It has suffered a few knocks over the years but I think it worth keeping in case it can be of use in future. The construction was again per Peter's article with a sandwich of hardboard and expanded polystyrene discs for the large section and a roll of lining paper stepped down in narrow strips for the small end. The whole thing being skimmed with filler and sanded to a smooth profile. The ring of screws on the end was for used to rotate it with a belt drive as it dried. I had a search to see if I had any photos or notes of the construction, but I could not find anything.


Attachments:
Former1.JPG
Former1.JPG [ 1.35 MiB | Viewed 189 times ]
Former2.JPG
Former2.JPG [ 1.31 MiB | Viewed 189 times ]
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 Post subject: Re: PAPER HORN
PostPosted: Mon Oct 19, 2020 4:10 am 
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Victor III
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Thank you John. Very interesting to see an important component part of the horn construction process which I know will be extremely beneficial to others in future when repeating the same exercise. Beautifully done and congratulations again.


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