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 Post subject: Difference between HMV 101 and 102 'arm'
PostPosted: Sun Mar 04, 2018 8:16 am 
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Victor III
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I noticed that at the end of the 'arm', where the sound box is inserted, the HMV 101 seems to have a metal insert where-as the HMV 102 does not have one

I just wondered why this would be.

Thank you very much for any information about this.


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 Post subject: Re: Difference between HMV 101 and 102 'arm'
PostPosted: Mon Mar 05, 2018 11:29 am 
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Victor IV
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I guess the internal metal piece in the 101 tonearm is designed to butt close to the opening in the back of the soundbox producing a continuous conduit ? Can't think of any other reason :? The 102 soundbox has a conical plug which presumably is designed to increase the air pressure behind the soundbox , perhaps doing this it then doesn't need a continuous conduit ? out of my depth here though


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 Post subject: Re: Difference between HMV 101 and 102 'arm'
PostPosted: Mon Mar 05, 2018 12:56 pm 
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Victor III
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Evidently all this is just matching the bore/design of the tonearm (which of course is the start of the horn system; on both models carefully designed but quite different) with the aperture of each soundbox where they connect. The "phase plug" in the 102 soundboxes is a mysterious thing but was clearly thought to have some beneficial effect on the sound.
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 Post subject: Re: Difference between HMV 101 and 102 'arm'
PostPosted: Mon Mar 05, 2018 7:12 pm 
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Victor IV
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In addition to reducing the size of the tonearm's throat, it looks like it certainly would add some weight to the end of the tonearm where it mates with the sound box, possibly forcing the #4 sound box to remain in a more balanced position--perpendicular to the record's surface. (Along this line, I'm wondering what the weight of the #4 sound box is compared to that of the Exhibition and #2.)

The Victor tonearms used on those models equipped with the #4 sound box--the VV-1-4, VV-1-5, VV-1-6, VV-2-30, VV-1-70, etc.--so far as I know, were not fitted with the inside tube. I know for a fact that the VV-1-5 had a conventional throat.

OrthoFan


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 Post subject: Re: Difference between HMV 101 and 102 'arm'
PostPosted: Tue Mar 06, 2018 9:18 am 
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Victor III
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soundgen wrote:
I guess the internal metal piece in the 101 tonearm is designed to butt close to the opening in the back of the soundbox producing a continuous conduit ? Can't think of any other reason :? The 102 soundbox has a conical plug which presumably is designed to increase the air pressure behind the soundbox , perhaps doing this it then doesn't need a continuous conduit ? out of my depth here though



Oh yes, I see what you mean. Different designs of the N0 4 and No 16 sound boxes required different 'arm designs.

Thank you
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 Post subject: Re: Difference between HMV 101 and 102 'arm'
PostPosted: Tue Mar 06, 2018 9:22 am 
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Victor III
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Orchorsol wrote:
Evidently all this is just matching the bore/design of the tonearm (which of course is the start of the horn system; on both models carefully designed but quite different) with the aperture of each soundbox where they connect. The "phase plug" in the 102 soundboxes is a mysterious thing but was clearly thought to have some beneficial effect on the sound.


I see - could you please clarify to me what you mean by 'phase plug' - which part of the hmv 102 is this please ?
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 Post subject: Re: Difference between HMV 101 and 102 'arm'
PostPosted: Tue Mar 06, 2018 9:31 am 
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Victor III
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OrthoFan wrote:
In addition to reducing the size of the tonearm's throat, it looks like it certainly would add some weight to the end of the tonearm where it mates with the sound box, possibly forcing the #4 sound box to remain in a more balanced position--perpendicular to the record's surface. (Along this line, I'm wondering what the weight of the #4 sound box is compared to that of the Exhibition and #2.)

The Victor tonearms used on those models equipped with the #4 sound box--the VV-1-4, VV-1-5, VV-1-6, VV-2-30, VV-1-70, etc.--so far as I know, were not fitted with the inside tube. I know for a fact that the VV-1-5 had a conventional throat.

OrthoFan


Most interesting. So some Victors didn't have the insert then. I have just weighed the No 4 sound box and it is just over 5 ounces.

I haven't seen any other 101's and assume they have the insert as standard but this is worth checking when I find another one to look at.

Thank you very much.
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 Post subject: Re: Difference between HMV 101 and 102 'arm'
PostPosted: Tue Mar 12, 2019 2:26 pm 
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Victor Jr
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The difference between the arms is indicative of the difference between two different systems.

Victor introduced the Orthophonic Victrola, with its radical new soundbox design and larger bore swan neck tonearm fitting, in the fall of 1925. Some time later, and I'm not certain when but it would have been between 1925 and 1927, Victor brought out their No 4 soundbox - a design that had been created in 1914, then shelved for over a decade - as a means for owners of older Victrolas with the narrower gooseneck tonearms to play the new electrical records more satisfactorily. The No 4 was also fitted to at least one portable and low-end table cabinet Victrola as well, but it really wasn't something Victor went out of its way to publicize.

By contrast, HMV went with the No 4 soundbox from the beginning of the electrical era in 1925. It was the heart of "The New Gramophone", along with exponential horns and a new swan-neck design tonearm. But my guess (and this is only a guess) is that HMV's engineers designed their system to include a smaller/narrower throat at the soundbox junction in order to increase the overall taper rate of the entire arm/horn assembly. The way to do that without making the No 4 incompatible with its US cousin (or the older tonearms) would be to keep the same outside diameter, but place the "real" fitting inside the outer tube. Which is precisely what they did, and it's on every single New Gramophone from the 101 portable to the most expensive cabinet models with gold plating.

If you compare the Victor and HMV versions of the No 4 soundbox, you can see immediately that the inner throat of the HMV version is much much smaller, and is designed to butt up against the inner tubing of the swan neck fitting used in all HMV New Gramophones, including the 101 portable. The Victor, by contrast, has a much larger throat because it was designed to fit the larger dimension of the older Victor gooseneck, which had no secondary inside tubing.

By the time HMV finally adopted the Orthophonic system, circa 1927 or 28, they also went with the corresponding Victor tonearm design, eschewing the idea of an inner narrow-bore parallel tube, and matched the 5a (and later 5b) soundbox to the same dimensions as the Orthophonic (which was known as the No 5 in England).


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 Post subject: Re: Difference between HMV 101 and 102 'arm'
PostPosted: Tue Mar 12, 2019 2:49 pm 
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Victor III
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shoshani wrote:
The difference between the arms is indicative of the difference between two different systems.

Victor introduced the Orthophonic Victrola, with its radical new soundbox design and larger bore swan neck tonearm fitting, in the fall of 1925. Some time later, and I'm not certain when but it would have been between 1925 and 1927, Victor brought out their No 4 soundbox - a design that had been created in 1914, then shelved for over a decade - as a means for owners of older Victrolas with the narrower gooseneck tonearms to play the new electrical records more satisfactorily. The No 4 was also fitted to at least one portable and low-end table cabinet Victrola as well, but it really wasn't something Victor went out of its way to publicize.

By contrast, HMV went with the No 4 soundbox from the beginning of the electrical era in 1925. It was the heart of "The New Gramophone", along with exponential horns and a new swan-neck design tonearm. But my guess (and this is only a guess) is that HMV's engineers designed their system to include a smaller/narrower throat at the soundbox junction in order to increase the overall taper rate of the entire arm/horn assembly. The way to do that without making the No 4 incompatible with its US cousin (or the older tonearms) would be to keep the same outside diameter, but place the "real" fitting inside the outer tube. Which is precisely what they did, and it's on every single New Gramophone from the 101 portable to the most expensive cabinet models with gold plating.

If you compare the Victor and HMV versions of the No 4 soundbox, you can see immediately that the inner throat of the HMV version is much much smaller, and is designed to butt up against the inner tubing of the swan neck fitting used in all HMV New Gramophones, including the 101 portable. The Victor, by contrast, has a much larger throat because it was designed to fit the larger dimension of the older Victor gooseneck, which had no secondary inside tubing.

By the time HMV finally adopted the Orthophonic system, circa 1927 or 28, they also went with the corresponding Victor tonearm design, eschewing the idea of an inner narrow-bore parallel tube, and matched the 5a (and later 5b) soundbox to the same dimensions as the Orthophonic (which was known as the No 5 in England).


Thank you very much for explaining shoshani.

A most interesting account of the reason why.
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 Post subject: Re: Difference between HMV 101 and 102 'arm'
PostPosted: Wed Jun 05, 2019 8:55 am 
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Victor Jr
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I'm revisiting this old topic because I made an accidental discovery the other day, one that really increased my level of respect for the lab-coated technicians at Hayes.

The swan neck of the tonearm of The New Gramophone had an inner tube and an outer tube; the bayonet fitting on the back of the soundbox would slide into a groove in the outer tube, just as it would any standard gooseneck, but it would of course clear the top of the inner tube which was something like 80mm on the outside and 78mm on the inside, according to my calipers. The inside of the backplate of the HMV No 4 soundbox had a throat opening of 78mm - the exact size of the inside of the inner swan neck tube, so that when fitted onto the end of the tonearm the two would connect together.

But. While the wider swan neck fitting for the 5/5a/5b soundboxes did not have that inside tubing, the inside of the backplate of both the 5a and 5b has the exact same 78mm throat opening. Which means that with the correct sized rubber isolator and brass ring (the socket into which that assembly was fitted was the same size on the backplate of the 4 and the 5a/5b), not only would the 5a or 5b fit a swan neck designed for a No 4, the fitting itself was fully backward compatible.

I'm actually putting this to a test; I recently picked up a pair of HMV 109 tabletop gramophones from a fellow TMF member, and while I put an all brass HMV No 4 soundbox on the older of the pair, I'm having our own MicaMonster fit a No 4 brass ring and his own proprietary isolator into the back flange of a spare 5a I have, specifically for the newer of the pair.


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