Re: Gilbert portable.
Posted: Tue Sep 05, 2017 3:00 am
I have redone the soundbox, after having received a different gasket tubing gently provided by Carlos. This material is much softer and thinner than the usual white tubing for Exhibitions, and closing the soundbox was much easier.
To evaluate the results without too much placebo effect I tried to use the smartphone as an audiometer. The increase in volume turned out to be quite negligible, however I think that the overall sound was better: less "tight" and with a bit more bass. I also think there was less wear on the grooves, and on the needle's point as well.
As the diaphragm seemed still pretty much compressed, I redone once more by trying to cut one of the tubing in half (originally, the soundbox had a sort of half-tube below the diaphragm). However, the half-tube has proven impossible to install inside the soundbox, as it tended to curl and wouldn't stay flat, how hard I tried.
I then tried to made a back gasket with a ring of high quality paper. With the paper ring, the diaphragm sits very low into the soundbox, however the soundbox itself is shaped accordigly and the diaphragm will not hit the back. With this paper gasket it looked as if there would be a lot of compression inside the soundbox chamber, and I thought that perhaps this compression was what the arm needed to sound at its best. Again, this solution was closer to how the soundbox was originally found. However, playing an actual record shown that there was no significant sound improvement, while it was evident that the needlebar could no longer stay in the vertical "neutral" position, and it was also clear that the needlbar could move very freely when pulling the diaphragm, but was basically stuck when pushing the diaphragm. (As a side note, this confirms that this type of diaphragm is very stiff, it should be considerd and treated like a mica diaphragm).
As the latter condition seemed unacceptable, also in order to prevent groove damage, I've redone the soundobox once again, re-putting in place the pair of soft tube gaskets provided by Carlos. Unfortunately at this point, having redone the work many times, the needlebar tiny screw was stripped and is held in place more by wax than anything else, and one of the two spring-loaded screws of the needlebar hinges shown sufferings too. Quite obviously I will stop here and be happy with the results. This is probably the sound that this gramophone can deliver and used to deliver; I was perhaps too much impressed by the arm design and expected something different.
To evaluate the results without too much placebo effect I tried to use the smartphone as an audiometer. The increase in volume turned out to be quite negligible, however I think that the overall sound was better: less "tight" and with a bit more bass. I also think there was less wear on the grooves, and on the needle's point as well.
As the diaphragm seemed still pretty much compressed, I redone once more by trying to cut one of the tubing in half (originally, the soundbox had a sort of half-tube below the diaphragm). However, the half-tube has proven impossible to install inside the soundbox, as it tended to curl and wouldn't stay flat, how hard I tried.
I then tried to made a back gasket with a ring of high quality paper. With the paper ring, the diaphragm sits very low into the soundbox, however the soundbox itself is shaped accordigly and the diaphragm will not hit the back. With this paper gasket it looked as if there would be a lot of compression inside the soundbox chamber, and I thought that perhaps this compression was what the arm needed to sound at its best. Again, this solution was closer to how the soundbox was originally found. However, playing an actual record shown that there was no significant sound improvement, while it was evident that the needlebar could no longer stay in the vertical "neutral" position, and it was also clear that the needlbar could move very freely when pulling the diaphragm, but was basically stuck when pushing the diaphragm. (As a side note, this confirms that this type of diaphragm is very stiff, it should be considerd and treated like a mica diaphragm).
As the latter condition seemed unacceptable, also in order to prevent groove damage, I've redone the soundobox once again, re-putting in place the pair of soft tube gaskets provided by Carlos. Unfortunately at this point, having redone the work many times, the needlebar tiny screw was stripped and is held in place more by wax than anything else, and one of the two spring-loaded screws of the needlebar hinges shown sufferings too. Quite obviously I will stop here and be happy with the results. This is probably the sound that this gramophone can deliver and used to deliver; I was perhaps too much impressed by the arm design and expected something different.