How to improve strangled B


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What could be the reason and how would you improve the situation when otherwise good sounding student violin (1920s, Laberte-H. 3/4) has weirdly weak lower part of the A-string: B-flat and B are lame and weak (strangled is the right word), C is better and D is normal.

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For a "reason", there is a natural dip in fundamental frequency power between the two main body resonances, and that dip is right where you say it is "strangled".  See the response plot below.  There could be other issues as well, but I'd guess this is the main one.  If this is correct, there's not a whole lot that can be done about it, as it is an overall character of the structure.  You could try moving the post around, and that might do a little bit.  One other possibility is a tailpiece resonance tuned to ~B, which could happen if the tailgut free length is fairly long, over 5mm I'd say.  If it is, try shortening the free tailgut length and hope for the best.

5a8d86046a95e_Responseplot.jpg.749c7b67c5421bdaa3580455f6c24462.jpg

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5 hours ago, antero said:

What could be the reason and how would you improve the situation when otherwise good sounding student violin (1920s, Laberte-H. 3/4) has weirdly weak lower part of the A-string: B-flat and B are lame and weak (strangled is the right word), C is better and D is normal.

It´s wolf note.

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1 hour ago, David Burgess said:

Don, would that also apply to his 3/4 size?

It would depend on the specifics.  I have a brick-like Seidel 3/4 size, and the mode frequencies are about a full tone higher than the average good full size.  If the 3/4 is thinner, it could be very similar to a full size for the structural modes.  

I suppose it is also possible that the instrument in question is extremely thick, which could raise the resonances so far that the "strangled" notes are in the gap between the A0 resonance and B1- resonance, but I think that is unlikely, and would sound exceptionally bad in other places too.

The tailpiece resonance issue shouldn't be any different.  It is also be possible that a chinrest resonance could strangle a note, so it might be worth seeing if a different chinrest makes a difference.

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4 hours ago, Don Noon said:

For a "reason", there is a natural dip in fundamental frequency power between the two main body resonances, and that dip is right where you say it is "strangled".  See the response plot below.  There could be other issues as well, but I'd guess this is the main one.  If this is correct, there's not a whole lot that can be done about it, as it is an overall character of the structure.  You could try moving the post around, and that might do a little bit.  One other possibility is a tailpiece resonance tuned to ~B, which could happen if the tailgut free length is fairly long, over 5mm I'd say.  If it is, try shortening the free tailgut length and hope for the best.

5a8d86046a95e_Responseplot.jpg.749c7b67c5421bdaa3580455f6c24462.jpg

Notice in Don's  plot the dip is deep at 500Hz so for a B note with a pitch frequency of 494 Hz the fundamental harmonic is indeed small as Don pointed out which could lead to a weak note.  But  for Don's instrument there is a peak at around 1000Hz so the second harmonic is fairly high and this B note might not be awfully weak.

A really bad situation would be having the deep valley at the 500Hz and another deep valley at 1000Hz so both the fundamental and 2nd harmonic would be small.  

A peak spacing of one octave is bad because it produces overly strong notes.  And a valley spacing of one octave is bad because it produces really weak notes.

A nice combinations are peak + valley or valley + peak.  

Bad combinations are peak + peak or valley + valley.

Even good makers like Stradivari sometimes had bad combinations which is one reason why some of his violins are great and some are only so-so.  I think this happens by chance.

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Thanks everyone, so far!

Your information is really very interesting, although I feel I can hardly do much about it!

Observations: the tailgut is ca 8 mm, I will see to it. The instrument plates are not extremely thick; it is quite reasonably built (not a masterpiece :) though) but still rather a top side of the (trade) range for 3/4: Le Couturieux.

I will let you know, what is the outcome.

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19 hours ago, antero said:

What could be the reason and how would you improve the situation when otherwise good sounding student violin (1920s, Laberte-H. 3/4) has weirdly weak lower part of the A-string: B-flat and B are lame and weak (strangled is the right word), C is better and D is normal.

Does it improve, or change with a new sound post / or sound post adjustment ?  Easy enough to cut a new post, looking for a better (perfect) fit.

 

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18 hours ago, Marty Kasprzyk said:

Notice in Don's  plot the dip is deep at 500Hz so for a B note with a pitch frequency of 494 Hz the fundamental harmonic is indeed small as Don pointed out which could lead to a weak note.  But  for Don's instrument there is a peak at around 1000Hz so the second harmonic is fairly high and this B note might not be awfully weak.

A really bad situation would be having the deep valley at the 500Hz and another deep valley at 1000Hz so both the fundamental and 2nd harmonic would be small.  

A peak spacing of one octave is bad because it produces overly strong notes.  And a valley spacing of one octave is bad because it produces really weak notes.

A nice combinations are peak + valley or valley + peak.  

Bad combinations are peak + peak or valley + valley.

Even good makers like Stradivari sometimes had bad combinations which is one reason why some of his violins are great and some are only so-so.  I think this happens by chance.

I should have added that all many of the adjustment suggestions proposed function by moving the various peaks and valleys around to avoid bad combinations.

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As suggested, I shortened the tailgut for 3...4 mm and it made some improvement: not a whole lot, but enough to notice.

Another observation: I played around a bit with the soundpost and it eventually fell over. And guess what - all strings and positions, including mentioned B had exactly the same power - in somewhat slightly sore way as it could be without a post.

So for now, with the same post slightly more south-west, it is already (not yet completely) better.

I haven't tryed different A yet - a radically different I probably don't have at hand -I don't keep very large variety for fractionals. What is a good steel - Prim?

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If you want to see if it's a tension issue or a resonance issue, detune the strings a whole tone down and see if playing a B (C sharp position) has the same issues. If it's resonance, the problem should still be there on the B sounding note. If not, I would look at the fingerboard as David suggested, or perhaps try some different strings.

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