Hmv xxx 12" tabletop in oak... This morning!

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nostalgia
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Re: Hmv xxx 12" tabletop in oak... This morning!

Post by nostalgia »

I am very impressed with your detailed work. I will also use this as manual for my first own restauration work, with the
15 euro machine I bought a few days ago. I will find out how I can separate the wood parts first, to not destroy the base.
Your photos also are very clear. You obviously are very committed and devoted to your work, I appreciate much the long detailed explanation you take your time to write during your restoration. Great to see a gramophone come back to life under skilled and loving hands and a caring heart:)

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Inigo
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Re: Hmv xxx 12" tabletop in oak... This morning!

Post by Inigo »

Thanks, nostalgia.
I really love this work, and the most important: sharing it for open discussion and mutual learning.
But I'm a bit odd in that, instead of being a purist in restoration as the original, I'm in the vein, shared by others on this forum, of trying to improve the performance of these machines with modifications that must be: 1) Reversible, and 2) as less noticeable as possible. My goal is that these machines, well made, are from a period when not all about sound transmission was implemented. This happened slowly with years, and the gained knowledge was implemented in New gramophone models, the old ones abandoned as obsolete. And at the same time, all the potential to apply these acquired knowledge with but small changes, is actually there in the old machines, and it's a pity to loss the opportunity. They simply were guided by the commercial side: each advance in tech promoted a new line of products better engineered. In this sense, it would have been a commercial failure to produce instead a kit for the users to introduce the improvements in their old machines...!
Now that no more new gramophones are being produced (well, at a commercial scale) we are in a different position. We are justified to analyze the potential of our old machines, and see how near they were from acoustic perfection. Of course, some ones far from the goal, but other machines are developed and constructed in such a way that only subtle judicious changes can improve their performance greatly. And that's my goal!
On the other hand, you must watch the experiments of some of our colleagues, or other people not in the forum, constructing really amazing acoustic machines, in the same old principles and with the same materials, but with all the physics of sound transmission well implemented. Search for the 'Ediphonic' in this forum, or the marvelous new EMG horns made by our friend emgcr, and the crapophones constructed by Hideki Watanabe (watanabehi) and you'll be amazed about what can be done!
In a humble side, watch my own YouTube videos, where I use a HMV 194 with an improved 5B soundbox, and judge for yourself the results... https://www.youtube.com/channel/UCpfs5B ... 6r5kMUd9ew
Inigo

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Re: Hmv xxx 12" tabletop in oak... This morning!

Post by Inigo »

In this case, the exhibition soundbox shows very hard supporting springs, and the compliance of the needlebar is low. This is matched, hopefully, with the low compliance of the small diaphragm and the compressed border of it, squeezed between two soft rubber gaskets.
The original sound was good volume. Even with the ossified and semi-cracked gaskets, and the hard back rubber isolator, air leaks and all, the impression I got was of a not too bad sound, and this in the street, open air and full of people talking and ambient noise. Or was I bewitched by the charms this machine and the perspectives of acquiring it...? :D
My experiment goes in the sense of going to a higher (matched) compliance value, to see what happens. Generally, this would lead to a higher volume and greater bass response. But certain limits must be respected; the size of the air chamber and its capacity to handle that sound, and the horn impedance.
All t this I'm doing by trial and error, as I don't have any means to measure such quantities... The only thing is to get another exhibition and maintain it at its original specification, just for comparison.
A higher matched impedance is gained thus:
1) relaxing the pressure at the diaphragm border, using softer gaskets, and unscrewing the back plate so it frees the diaphragm movement.
2) freeing the needlebar movement. The inclusion of soft rubber washers at the springs in series with the hard springs lowers the total compliance.
Theoretically the compliance of 1 must correspond with 2.
The third compliance is that of the back isolator. But this is different. If too compliant, the energy of vibration will escape by this point and less energy goes to the diaphragm. If too hard, the energy it receives will react against the tonearm inertia, the results being that part of this energy will bounce back to the needle and act against the grooves, wearing the record fastly.
These soundboxes were state of the art in its epoch, and they were intensively tested on the Gramophones they were designed for. So any changes must be light and subtle, and very careful.
Will continue...
Inigo

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Re: Update HMV style 3 LCO - Exhibition soundbox

Post by Inigo »

I've already received the new back rubber isolators through a generous member of this forum. Originally made by Ron Stiko. Very nice. At last I can start experimenting with this soundbox, completely new for me, although I already owned an exhibition junior soundbox. But that's another story.
Ive managed to overhaul the soundbox with the original diaphragm (which seems OK) and new gaskets. But I'm using new rubber tubing gaskets from that eBay swedish provider, as sold for the Meltrope soundbox. They seem to be of adequate size (similar in size to the original dried ones) but I've observed several things that make them not work properly.
First, they are soft. But to make them enter into the soundbox is a bit tricky. And once installed (a nightmare) with the plate completely screwed, the gaskets are pretty squeezed.
Secondly, after a while, the front gasket pops out of the soundbox ring. It simply won't stay in place.
I've noticed that this soft rubber tubing must not be natural rubber; I don't know what kind of rubber it is, it has no trace of 'grip'. You can slide your fingers along the tubing without feeling any trace of the 'grip' natural rubber has. This could be part of the problem. The other being that I'm using too thick gaskets. But probably, if these gaskests were made of natural rubber, the grip would prevent the front gasket from escaping the ring.
Strange problem. I have another new tubing, bought from an indian eBay seller, which seems to be natural rubber, but I'm afraid these would squeeze the diapragm border too much.

Is there any trustable supply of gasket tubing adequate for the exhibition soundbox? I should try that. Could any of you tell me where to buy that?

I'm planning to experiment with the exhibition, moving the behaviour to a different point which has given great results with other HMV soundboxes. This is to move to another softer compliance working point: relaxing the pressure on the diaphragm edge and relaxing in parallel the pressure on the balance springs by means of rubber washers. My previous photos show the soundbox assembled this way, but the lack of a back isolator prevented me from testing it. Also, new glass diaphragms provided generously by another member will be tested.
But I'd also like to have another exhibition, just to keep one tuned to the original specification, and doing the tests with another soundbox, to be able to compare.
Anyway, I've finally managed to assemble the soundbox using a smaller bore gasket for the front ring, which remains in place. I've tested it and the sound is good, but a slight blasting in high notes (of Sarah Martin) is disturbing. Softer records sound better. Yet a bit of delicate tuning is needed, and of course, installing the proper rubber gaskets of original size.
Will report later...
Inigo

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Re: HMV Model 3 (ex L.C.O.) 12" hornless tabletop UPDATE

Post by Inigo »

Thanks to members of this forum who have helped a lot, especially to soundgen, mattrx, WDC and jamiegramo, now I have rebuilt my Exhibition soundbox with new gaskets of the proper size, new back rubber flange and a marvelous glass diaphragm. I've also modified the air chamber, relaxing the pressure on the gaskets to the minimum airtight, and filling the gap between front ring and backplate with a stretched strip rubber band. I've also added rubber washers between the balance springs and the screw heads, so the compliance both at the needlebar fulcrum and at the diaphragm edge is greater than the original specification.
I've also added a transformed copper elbow at the soundbox throat, which acts as an intermediate adaptor to correct the bad tracking angle of the original configuration gooseneck tonearm.
IMG_20190915_123432.jpg
IMG_20190915_123418.jpg
IMG_20190915_123403.jpg
IMG_20190915_123316_1.jpg
Now all is drying, and this afternoon I'll make some tests and load videos on my YouTube channel.
The latest video I uploaded was this machine, but the exhibition soundbox in original configuration: original mica diaphragm, compensated gaskets (because I still had no proper size, so it was ambled with a thicker back gasket and a thinner front one). The diaphragm screw is not sealed with wax, for the soundbox was only temporarily assembled. Nevertheless, you can see it in action, with a Decca Mildred Bailey record (very kind to any gramophone) and bamboo needle. It is in Test I video here: https://youtu.be/4tVigBi43P4
I've done some more videos on this configuration, which I'll also upload later.
After these, I will add the Test II videos, using the new exhibition configuration. More info will follow, for those interested in 'anorak' experiments... 8-) ( ;) jamiegramo). We will see how it performs...
Inigo

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Re: Hmv xxx 12" tabletop in oak... This morning!

Post by Oedipus »

This is a Model 3, made from 1913 until 1923; from July 1922 it was (in the UK) re-named Model 58, but this had a dark oak case (as did the last Model 3s), and was normally over-stamped 58 on the label on the base. From the start, the Model 3 had a cast iron horn, as did the smaller 1a, though not the Model 1, which had the motor-in-horn arrangement. Model 58s also normally have needle bowls.

The position of the brake and speed control do not indicate a change of model number, merely a change of motor, which can affect the position of the speed control. Over a ten-year production run, particularly at that time, when the war interrupted the inception of motor manufacture at Hayes and import restrictions affected the available stock, motors could vary.

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Re: Hmv xxx 12" tabletop in oak... This morning!

Post by Inigo »

Have you all seen what a beautiful preparation of the soundbox for more compliance, etc...?
I must tell the truth: after some testing, I've discarded this configuration. It sounded horrible! The blasting and fuzzing was terrible... After adjusting the balance screws it didn't improve, so I blamed: 1) the rubber washers on the balance screws; this simply didn't work, and adjusting the screws with these rubber washers is a nightmare; I've switched again to the felt washers, much more kind on adjusting. 2) the gap sealed with the rubber band; I've removed the rubber and freed the backplate; after some twisting, it's clear that the factory setting, full pressed backplate, gives a ringing sound at the treble with less bass, and if relaxed, it does less ringing on the treble and increases the bass; it has to be adjusted again.
What is clear to me is that exhibition is a very different affair from the no.4, and things that work there wouldn't work here. The balance screws are a difficult matter...!
Will continue until I get a satisfactory solution.
Acoustic records with loud tone needles sound very shrill. Electrical records with thin soft needles sound acceptably good, even a loud singing baritone passage I've been testing time after time had a good sound, but a little buzzing that must be corrected.
What has been a success is the tracking adaptor. The soundbox has no noticeable deviation at naked eye, and electric records on loud passages don't wear. A little marvel! Still I must do a measurement with the protractor and register the degrees of error for the record. Will continue reporting...
(The YT videos will have to wait...)
BTW, i am having problems with the orientation of videos when uploading. I see them straight on my pc, but when uploaded, some get sideways, and i cannot find how to correct this! :oops:
Inigo

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Re: Hmv xxx 12" tabletop in oak... This morning!

Post by Inigo »

I've just extracted the springs again, cleaned with towel paper and a cloth, and reassembled. I've made the mixture of molykote and graphite, 12 spoonfuls molykote and 3 of graphite powder. I've filled the barrels with this mix, well spread inside before mounting the springs, and a bit more between the coils after the sittings were installed.
I've seen that part of the noise comes from the bull gear and the spindle worm. Moving the hear with nude hand, it makes the spindle rotate, but with noise. I've added some of the spring graphited grease to the spindle worm, and it seems to reduce the noise a bit. But I suspect this is the main source of noise. I've installed the thin washers on the spring arbour at the same places where I found them, one just under the lid of the bull gear side, and another at the opposite, just between the arbor and the screwed stanchion. The gearing seems to run well, despite the noise. But I'm afraid this could make the motor to loose power, although it is at the most powerful gearing... this should be hardly noticed... Will continue. I'm now going to assemble the motor and adjust the governor.
Inigo

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Re: Hmv xxx 12" tabletop in oak... This morning!

Post by Inigo »

The heavy runner again!
Testing the motor with regreased springs did well. After some running, the motor moves the spindle e with only one turn of the crank from the zero-power status. Good.
Assembled and with the turntable load it's the same, but s full winding plays two 12" sides, not bad, provided the springs are the original ones, or an old replacement, for they are stamped with the Victor brand at the outer end.
I've also done soundbox tests. The exhibition has new rubber gaskets (thanks, soundgen), new rubber isolator from Ron Stiko (thanks, mattrx), and new glass diaphragm to which the needlebar is attached with epoxy (thanks, WDC). At the back I've installed a tracking corrector (thanks, jamiegramo) made from an old sample I cut years ago from a standard 18mm (or ⅝" approx) 45° copper elbow, made for experiments with other soundboxes, probably the no4. It simply fits almost perfectly to correct the error of my exhibition installed on the gooseneck. I've simply adjusted it a bit, and glued onto the back connection using Pattex, something like Elmer's vinyl glue mixed with a white filler that gives it a certain thickness and consistency. The other end had a pin properly installed which gives the needle a 50° angle with the record. It only needed a thin newspaper strip to help airtightness. I painted it black with water enamel. Still the soldering of the pin has a rough aspect; it would need some filling out of the external protuberances and irregularities of the welding, to give it a better look.
I did some tests in factory adjustment after the failure of previous experiments (see photos in previous posts) removing all the added rubber padding and assembling it as originally intended. After some tweaking I managed to set the screws at a good point, and the sound was good. Still, harsh with loud acoustic records, and better with electrics, specially when using thin soft steel needles from dear old friend Barry Williamson, at Phonoservice, Liverpool. These are as good as the needles from soundgen, but a bit thinner. Soundgen soft steel needles also work wonders with electrical records. Still I've not tried bamboos again with the exhibition, for I ran out of bamboos with rounded shank; I must cut a supply.
The balance springs on my exhibition are incredibly thick, and hard. It's not at all easy to set them properly. I had to turn the screws only a fraction, proceeding by ¼ or even 1/16 of a turn from test to test! The problem is to set the securing nuts once you arrive to a good status of things. They tend to rotate the screws too! Three hands are needed for this work!

After these tests, still I insisted on relaxing the backplate by unscrewing until the pressure on the gaskets is soft, as needed for airtightness and no more. Simultaneously I added again the tiny felt pads under the balance screws. This makes easier to adjust them to a lower pressure on the springs, and eliminate some of the buzzing. I've not yet arrived to a conclusion about of the sound improves or not. I need to get a second exhibition comparison... But they are so expensive... The Gramophone costed me almost the same as a good exhibition!
After another test, at least four acoustics it is better in its original configuration (backplate fully screwed in). Still I've left the felt washers, for they seem to help with these hard springs. With electrics, there is a sensation of less bass, but the wind is clear and crisp, with no distortion. Soft thin steel needles.
Inigo

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Re: Hmv style 3, 12" tabletop in oak. Revert to standards.

Post by Inigo »

After regreasing the springs with Molykote and a bit graphite, as per Marco's advice, and several weeks of use, I must say that it works like a champion.
But I've ended my experiments with the Exhibition. Another trial was done with the relaxed pressure on the backplate, sealing with vinyl glue and all that, plus the felt washers between the screws and the balance springs. After several weeks of use, I must say that this doesn't give a satisfactory sound with this horn. The altered Exhibition gave a slightly deeper sound with more bass. But this didn't sound good on some strong acoustic recordings. It had a resonance that definitely sounds better if moved upwards in the frequency spectrum. The famous ringing tone of this soundbox is better placed as it was originally, at least when associated to this machine horn. I've reassembled and adjusted the soundbox again in its original configuration, and the sound with acoustic records is definitely better this way.
The transformation of the diaphragm and balance springs compliance works well with no4/5 soundboxes and larger horns, but not here. It seems that the small Exhibition in the original adjustment was well suited for these smaller horns, judging by the overall sound.
And I'm surprised that this machine sounds better with loud steel needles instead of soft ones. The treble sounds better, and with a louder volume, but the overall sound is much better... Certain records sing with a very natural sound... It's clear to me that the original design was better for acoustic records of the era.
Still there's one only modification I've retained, and it is the added elbow connector for correcting the tracking angle. It works very well, and I'm most confident playing records on this machine without damage.
Regards,
Inigo

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