Experimentation with an Exhibition Soundbox

[Governor Flyball]

I was looking for something softer for the gasket. I searched around and found this. It is 3. mm OD 1.3mm ID surgical tubing. It is very soft an elastic and provides a good seal. It worked well on the Exhibition and I plan to try it next on a Victor No. 2.

https://www.ebay.com/itm/176221867862?var=475672384831

[jamiegramo]

I was looking for something softer for the gasket. I searched around and found this. It is 3. mm OD 1.3mm ID surgical tubing. It is very soft an elastic and provides a good seal. It worked well on the Exhibition and I plan to try it next on a Victor No. 2.

https://www.ebay.com/itm/176221867862?var=475672384831

Thanks for posting that link although I can not see the size small enough that you quote. It’s in China but they don’t ship to the UK! I never saw that before.

[jamiegramo]

I am glad others have been surprised at the tracking error at the beginning of the disc. I like the 15 degree correction. However to provide a a good average tracking correction, you would need to move the needle arc forward ahead of the spindle. This would then mean that the tracking force towards the center of the disc as there would be no anti skate force to counteract ir. It begins to get more and more complicated! I made a similar compromise in a Columbia Grafonola 50 to reduce the tracking error at the record outer start and accepting a slightly increased error at the record center.

I wonder if they thought about such things in those far off days?

In tilting the reproducer forward to create less tracking error this does create too much overlap (the distance the needle goes past the spindle). However I believe the benefit does outweigh this. I have not noticed a problem with the tracking force in my experiments. I made a few adapters that tilted the reproducer into correct alignment but also pushed it back to achieve best overlap.

[Governor Flyball]

Curious. I earlier posted the eBay source of my gasket material but it has disappeared. I bought some surgical natural rubber tubing from China. It is extremely soft and provide a good seal.

https://www.ebay.com/itm/176221867862?var=475672384831

[Hoodoo]

That latex gasket tubing might be worth a try, though I am happy with the regular white tubing sold by a number of suppliers.
In my earlier comment I was referring to the black rubber isolator that contains the ring to mount the reproducer to the tonearm.
The equivalent part on my Meltrope (and EMG reproducers) is much softer.

[Inigo]

I feel the same about modern rubber gaskets, seem harder than old natural rubber...

[jamiegramo]

Very interesting.
My experiments go in that direction, also trying several home made diaphragms made of metal, plastic and cardboard:

Inigo, did any material stand out as better than others for diaphragms? Let us know if you can. Did you try plastic coated cardboard or laminated cardboard? There’s also materials like compressed foam.

[CarlosV]

Did you try plastic coated cardboard or laminated cardboard? There’s also materials like compressed foam.

Some of these materials were used in Edison diamond disc and Opera diamond B reproducers: I utilize a diaphragm made of what looks like compressed foam that produces a marvelous sound, but its creator does not make them anymore. Wyatt Markus produces one made of dollar bills (!) glued together, and it sounds nice, much better than the original, although not as good as the foam - he also made a diaphragm like that for the HMV/Victor nr 4, that sounds good but I removed it because it looks very strange with part of George Washington's face instead of the black background, and it also hides the words etched inside it. There is no such problem with Edison reproducers, as normally the diaphragms are not visible.

[Inigo]

Very interesting.
My experiments go in that direction, also trying several home made diaphragms made of metal, plastic and cardboard:

Inigo, did any material stand out as better than others for diaphragms? Let us know if you can. Did you try plastic coated cardboard or laminated cardboard? There’s also materials like compressed foam.

Those two black are made from very thin and stiff, fine corrugated cardboard, and sound good, but too stiff, and gave no treble... My comparison corner stone is HMV no5a/b.
The others are all metal (kind of) from food trays, dessert cups lids, wine bottles caps, etc. They all sound well, but not too well, lack of treble too, certain tubby sound. I don't know if to blame the material, the diaphragm corrugations or the small air chamber of the Exhibition, which I suspect too small to offer a good cushion for a too compliant diaphragm. The material is not true metal; si those are made of thin tinplate or aluminium foil, covered by thin plastic material by both faces. I think the plastic provides resistance, but kills the ease for transmitting the high frequencies through the metal. The thinner among these sound better, but are too delicate. I have to buy thin gauge duraluminium sheet to try that...
I've not tried yet some plastic I've got from the bottom of certain food trays, which is round, very thin, stiff, and has impressed some corrugations in the shape of crossed diameters and concentric rings... When scratched with the finger tip it sounds promising... Seems to pass the treble. But I've not yet tried it on the soundbox.
I have a dedicated box with many materials for future experiments, as stiff thin paper, several types of thin metal sheets, cardboard, plastic, and foam sheets. I've read somewhere that the pressed foam can be made from thin styrofoam sheets pressed under a heated iron... I have to try this also.

[Orchorsol]

I've bought natural rubber surgical tubing from China before but found it degraded very quickly, starting to revert (rubber technical term for crosslinking breaking down chemically) to gum and crusty sulphur within a year - very poor quality. Your mileage may differ of course! I prefer to use a known reputable type of NR tubing which I know a number of EMG enthusiasts use - the same material that's used here in the UK for vintage bicycle valves.