Who has done work on needle bar/diaphragm resonance and mass

[JerryVan]

Do you place the putty directly on the mica, or does it suffice to attach to the needle bar, just adjacent to the mica connection?

[PeteLeoni]

On needle bar not on mica, thus:

[PeteLeoni]

Right on the crook is perfect for the #2
Not going anywhere and that stuff is remarkably stable. If any of you have ever used it, it does not dry up or get hard. Pretty much pure titanium dioxide. I think that tungsten putty might be even better, it's what I used on my acoustic guitar pickups but I have none handy. At any rate this is great. Vernon Dalhart
"The Letter Edged In Black" Never sounded so good on a Victrola.
Now that there record is will jerk a tear from a statue.

[PeteLeoni]

And yes I will post a video.

[PeteLeoni]

And yes I will try tungsten putty instead of beeswax because that would probably seal just as well plus add mass. Tungsten putty is very flexible may seal well.

[PeteLeoni]

I ordered the tungsten putty. It's about the same weight as lead so about half as much should work. And I will try it on the inside around the screw which would make it virtually invisible. No more poor sound out of the #2 reproducers would be a winner. I am looking for a reasonable #4 to rebuild as a baseline since everyone seems to think that's the best compromise.

[PeteLeoni]

Even though I seem to be (almost) the only fool that's into this right now (I think that is gonna change) I want to report that the lowly #2, when tuned and damped with the titanium putty, is the best sounding one of all of the (properly rebuilt) drivers between
Exhibition, #2, and a Silvertone that uses Exhibition type mica and gaskets. Honestly a phenomenal improvement. Video soon.

[CarlosV]

Even though I seem to be (almost) the only fool that's into this right now (I think that is gonna change) I want to report that the lowly #2, when tuned and damped with the titanium putty, is the best sounding one of all of the (properly rebuilt) drivers between
Exhibition, #2, and a Silvertone that uses Exhibition type mica and gaskets. Honestly a phenomenal improvement. Video soon.

Did you add the putty in the inner side of the diaphragm? and how do you determine the correct amount? trial and error? It will be nice to see and listen to the video, it is always fun to improve on the performance of such machines!

[Orchorsol]

If you haven't already, may I suggest reading Wilson & Webb: https://www.gramophonemuseum.com/images ... s-1929.pdf

[Lah Ca]

The use of the putty is probably analogous to what has been done with violins, cellos, and guitars (and such) in an effort to eliminate wolf tones (loud, shrill, unwanted resonances, usually at specific frequencies, but sometimes broader spectrum). Ironically, higher end instruments are more susceptible to wolf tones because they are very acoustically live. Frustratingly, the wolf tones are often seasonal, even when instruments are kept in a humidity controlled environment. Wood is organic and is constantly changing with humidity and temperature. Anyway BluTack has long been used as a temporary, non-invasive solution. Wolf tones can sometimes be mitigated by moving a chunk of BluTack around an instrument's top until a spot is found where the BluTack will dampen the resonance.

In my reading, I have noted claims that increasing the mass of bee's wax (which can be worked into a soft pliable putty) on the needle bar where it joins the diaphragm will change the sound of the reproducer and can mitigate harshness or shrillness in the sound.

On one of the reproducers for my 1920 Aeolian Vocalion machine, someone, in the distant past, had doctored the needle bar with a thick paste of shellac, which I assume might accomplish the same thing as the putty but with a lesser dampening effect. Upon taking the reproducer apart to rebuild it (which involved using alcohol on the shellac), I discovered that the layers of mica where the needle bar attaches to the diaphragm had started to separate. The shellac may have been an effort to extend the effective contact surface of the needle bar out past the damaged area of mica and get rid of any unpleasant sound caused by the separating mica.