Violin Forum/Message Board

[actonern]

Over and over we're taught by those that know how important it is in optimising the sound of an instrument to ensure the sound post fits really really well against the plates.

One thing I tried recently, and am throwing out there for anyone else inclined to try it, is to take the thinnest (and never used!) feeler guage that comes in the set and snip off a section about 4 cm. long. I'm talking about the ones that are like sheet metal, not the wire ones for gapping spark plugs. Insert about half that length into a small stick that's easily narrow enough to fit through the sound holes.

I discovered that lots of posts that I had previously fit, as carefully as I was able, (looking in through the end pin hole for gaps and rotating the post on axis to see if it wandered etc), were not fit good enough... the thin feeler guage would slide in a bit. Nudging the post till it fit against the back plate with no ability of the thin metal to slip in made an amazing improvement in sound.

It may not be of any use to those of you that have developed a feel for these things, but it is a handy and very easy way to identify obvious problems.

And on cellos! Wow does it reveal misfit posts!

The guage I'm talking about is really thin... foil like thin, but because it's made from tough steel it will work fine, unless abused. To use it, you just poke the stick with the foil on the end through the f holes and it will bend along the flat of the back and you push up against the post edges to see if it can slip in anywhere.

I haven't figured out a way to do the same to the top plate post interface, but someone very knowledgeable let me know that the top plate post interface is not "as critical" as the back plate interface fit.

Best regards,

E

[kjb]

interesting< I was having a difficult time picturing you doing it to the top plate until I read further. are you using a mirror also?

[actonern]

I do use a dentist mirror... but that really only gets you "so" close...

The time tested method of sticking the pointy end of the adjuster into the slot of the post and gently rotating it will also reveal posts that are on edge and not flat to the plate. I use that method with the mirror on the top plate.

Plus, (and I'm only going on a hunch here) if the post fit against the top plate is within a thou or so, the fibres of the spruce will in short order crush to effectively have the post fit very tight across the diameter...

E

[pmccombs]

[actonern]

Perpendicular...

I may have conveyed the wrong impression about a "crush fit."

It's not to encourage sloppy work, its just that a post end can, at a sufficiently small tolerance level never be fit "perfectly."

I'm just not prepared to believe that anyone can fit it to 1/10,000 of an inch accuracy... at some point it has to be declared "good enough" and because the wood of the top plate is relatively soft, time and pressure completes the 100% fit.

Looking at old tops off the instrument shows that indeed the post does indent the top, and not just in cases where abuse has occurred from improper adjustments...

E