Little Thorens Gramophone

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jboger
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Re: Little Thorens Gramophone

Post by jboger »

mrrgstuff:

Interesting to watch you dismantle your reproducer. May I add my two-cents worth? I would re-use the mica; it's totally salvageable not to mention original to the soundbox. You surmised that the inner brown paper is original. I believe it is. I have another Continental reproducer (Swiss?) that had such a textured piece of brown paper inserted inside. It serves no purpose other than to be decorative, so one doesn't see the bare metal behind the mica. My paper had become so deteriorated and brittle that it simply disintegrated.

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mrrgstuff
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Re: Little Thorens Gramophone

Post by mrrgstuff »

jboger wrote: Mon Mar 29, 2021 9:06 am mrrgstuff:

Interesting to watch you dismantle your reproducer. May I add my two-cents worth? I would re-use the mica; it's totally salvageable not to mention original to the soundbox. You surmised that the inner brown paper is original. I believe it is. I have another Continental reproducer (Swiss?) that had such a textured piece of brown paper inserted inside. It serves no purpose other than to be decorative, so one doesn't see the bare metal behind the mica. My paper had become so deteriorated and brittle that it simply disintegrated.
Thanks for watching the video :D

The mica is indeed in better condition than expected, although has a bit of a split at one point and a portion of delamination. I have already made a replacement plastic one (next video) and cleaned up the mica one too. I certainly plan to try the plastic one, but may also put the mica one back in for comparison.
The wax on the outside and the modifications to the back may have fooled me into thinking this was less original than it actually appears to be.
I think I have ruined the backing paper :( but should be able to replace, its nothing very special.
Just deciding now what to do with the main body. The dull grey effect I think is oxidisation. The metal I think is spelter or pewter or some other pot metal like alloy. The clean metal is a sort of straw colour, not brass.
Thanks
mrrgstuff

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mrrgstuff
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Re: Little Thorens Gramophone

Post by mrrgstuff »

I've now made a replacement diaphragm, but not yet fitted it. It seems to have more of a 'ring' than the mica one, but its also thicker which might compress the gaskets too much :!:

https://youtu.be/BSfWrBLuN_M

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Inigo
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Re: Little Thorens Gramophone

Post by Inigo »

Your experiments are very interesting. I've also made some copies of the Meltrope diaphragm with thin aluminium sheets from food trays, and they sounded as good as the original. I keep a box full of bits of things I collect that seem suitable for diaphragms, as thin stiff plastic sheets, thin porex sheets, metals, etc. for experimenting. I've read that the better phonograph diaphragms made by a fellow colleague are the truetone ones, which I read somewhere were made from pressed porex material. I want to try it myself.
I keep in that box any bit of modern materials that I feel sounds 'gramophonic' when scratched with a fingertip.
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jboger
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Re: Little Thorens Gramophone

Post by jboger »

mrrgstuff:

I have watched your videos with interest and like what you are doing. I do have a couple of comments (don't we all?). For this type of reproducer, one in which the diaphragm is inserted through the front, I have found the original mica to be a bit oversized compared to the opening. The thinness and flexibility of the mica provides some "give" so one insert the mica. You of course can not do that with the cd case. Now I would like to make a prediction. I believe your new diaphragm is too thick and rigid to set up a good sound wave with sufficient amplitude; it may vibrate with the needle but not really flex. But we are all good experimentalists and the proof's in the pudding. So I wait to be shown wrong.

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mrrgstuff
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Re: Little Thorens Gramophone

Post by mrrgstuff »

jboger wrote: Sun Apr 04, 2021 9:50 am mrrgstuff:

I have watched your videos with interest and like what you are doing. ... I believe your new diaphragm is too thick and rigid to set up a good sound wave with sufficient amplitude; it may vibrate with the needle but not really flex. But we are all good experimentalists and the proof's in the pudding. So I wait to be shown wrong.
Thanks :D I find this sort of technology fun to play with

It has taken a while, but I have now got the soundbox back together. The thicker diaphragm was a bit of a squeeze but I have also been experimenting with different types of materials for gaskets and found something which works:

https://youtu.be/IkCCI8Vvisk

There are some sound tests at the end and I would be interested in hearing what you (and anybody else) thinks :?:

Thanks :P

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Inigo
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Re: Little Thorens Gramophone

Post by Inigo »

MHO... volume is adequate, but freq response is severely curtailed, both in the treble and the bass. A good, thin and stiff mica diaphragm with supple gaskets gives a much better and clearer sound. You're also aware of this, and my observations don't have the intention of make you disappointed, absolutely! In the other hand, I encourage you to experiment with this same arrangement to see how far can it go in delivering a good sound... to find its true limits.
My advice is to try this same diaphragm with more compliant gaskets. The stiffness of the diaphragm is an advantage, although it's higher mass than the mica ones will filter out the treble. Anyway, my guess is that using softer gaskets will improve the bass and the overall volume, although the diaphragm mass filter will continue killing the treble.
I've read somewhere that Bob Waltrip used a soft silicone caulk instead of rubber gaskets, and this makes the diaphragm more like floating between the very flexible silicone rings. This will also have a counter effect, undesirable, which is that the weight of the soundbox will tend to press the diaphragm out of its equilibrium position when the soundbox weight rests on the needle. This effect is partially counteracted by the gaskets stiffness, so if you reduce it too much, that bias on the diaphragm position will take its lot on the resulting sound. Besides that, due to lateral forces of the record and a slight wow in the grooves, the weight momentum on the diaphragm will be unstable, so that bias may derive from one side to the opposite, rendering the sound variable. So the gaskets must be softer, but not too much. A nice problem to solve. The commercial solutions were always a compromise between all these opposite effects, and undoubtedly, the best solutions are in the orthophonic line of soundboxes.
Inigo

gramophoneshane
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Re: Little Thorens Gramophone

Post by gramophoneshane »

jboger wrote: Sun Mar 14, 2021 9:30 am I picked up an internal horn Thorens gramophone recently at a local auction. I have found on line a number of Thorens catalogs, 1907, 1910, and 1914. The latter depicts a model called a No. 201 Sphynx, which has some similarities with mine (primarily the grill in front) but also significant differences. I have not found too much on line about internal horn Thorens. Perhaps someone could point me in the right direction. If someone has the same machine or something like it, could you post a picture?
What a great little machine.
I've never seen a round Thorens motor before.

jboger
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Re: Little Thorens Gramophone

Post by jboger »

Mrrgstuff: Sounds pretty good. Wasn't expecting that.

Gramophoneshane: In my area, at the local auctions I go to, I see, of course, mostly US phonograph-related items. But here and there I see foreign machines as well, such as this little Thorens. I once saw a day-night phonograph (which I think was French), an outside-horn Zonophone (which I think was English), an ugly Pathé (if I recall correctly), and plenty of Swiss music boxes. What I'd like to see, not necessarily buy, would be a non-US cylinder machine like a Pathé. That I haven't seen.

I've seen these machines advertised at the higher-end auction houses here in the States, but those are not the sort of auctions I go to. My sort of auctions have everything dumped on tables, and there might be as many as three people calling bids: one selling furniture, another jewelry, and a third selling whatever. When one table is done, we move to the next. We follow the auctioneer around the room. There's seldom any order in which items are sold. One item might be a glass vase that sells for a buck, the next might be a stoneware crock that sells for a thousand. There's no telling what an item will sell for. It all depends on who comes that day. Just because these auctions are at the opposite end from Sotheby's, however, doesn't mean things can't sell for a pretty penny. They most certainly do.

Covid-19 shut most of this down for the past 1-½ years and a lot of auction sites have moved on-line. But now that the pandemic seems to be subsiding, many of the live, on-site auctions are returning.

Anyway, that little Thorens with the round motor was bought at one of those local auctions that I describe above. Probably more than you wanted to know.

John

gramophoneshane
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Re: Little Thorens Gramophone

Post by gramophoneshane »

jboger wrote: Mon Mar 15, 2021 3:03 pm It's a long-neck.
Actually, no its not. Not in the true sense.
It's just the common European style used but most German and Swiss manufactured soundboxes that didn't use a bayonet fitting. Some have a locating pin or screw and some don't, as some tonearms have a slot for the pin or screw and some don't.
They also made adaptors so a bayonet fitting soundbox can be converted for use on a non- bayonet arm, and visa versa.

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