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1st.. Jan. 2021

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 Patrick Kreit’s book.

     I did develop an theory over the last few years based on combining Dr. Harris’ and Carleen Hutchins’ work, but it dawned on me a year or two ago that the significance of plate weight at the heart of Dr. Harris’ idea of plate stiffness figure mentioned above is easily tested: I just needed to make a violin with a heavy front and heavy back plate, and

 -  see where the key 6 resonances below 600 Hz fall, and

- what it is like to play: the tone and response under the bow.

    Fortunately, with practice, the key body resonances under 600 Hz are quick and easy to measure, and if the weight of each plate really is a significant factor then the violin with heavy plates would probably turn out to have low key body resonances, in particular B1- and B1+.

Results

   With a heavy back and heavy front (belly) I found that taking an old Maidstone Strad-model violin to pieces and reassembling it (in fact with a new heavy maple back I made) showed that the weight of the belly and back plates had little effect on any of the key body resonances.

          Most importantly, B1- and B1+ resonances. The belly is 17 to 20 grams too heavy (at 82 grams), and the back 25 to 30 grams too heavy (at 127 grams). The Maidstone, originally a very cheap violin for beginner students dating from about the year 1900, now plays very well and easily and with good tone, especially on the A and G strings. Details of all the parts and final body resonances can be found here as a .pdf page using the format laid out below. Dr. Harris’ theory implies that the key body resonances would be low if the plates have normal tap tones, but they were not.

     The profound limitations to Dr. Harris’ work have shown up too in Jo Curtin’s work, published in The Strad Journal: see this page and revealed by his his article on Strads. The effects of gluing each plate to the stiff bouts seems to dominate!

Patrick Kreit.

     Several years ago  Patrick Kreit (on the right in the photo) published “The Sound of Stradivari”,  an excellent book on violin-making  (costing € 485 now).

  Mr. Kreit links the Mode 5 frequencies of the violin's  plates to the resonant modes of the final violin body, step by step, and describes the only step-by-step method I have ever come across to make the lightest possible plates. That matters.

    He has done 20+ years work in exploring the relationships between violin plate's resonances (Mode 2 and particularly Mode 5) and the 6 key body resonances: see the ‘Resonances of the Violin body’ page.

Simple theory

   As I said, I have concentrated on getting the tap tones of the plates where I want them, but tap-tones are just a part of the whole: the internal air volume, f-hole area, the arching, the body length, the sound-post and the bridge must all be right too.

    My findings are that Carleen Hutchins broadly got it right: if you set the Mode 5 tap tone of front and back with the belly just a few Hz below the back  at 340 to 350 Hz (measured with low moisture content in the wood), your fiddle can turn out sounding really good! There is much more detail on the ‘Plate Tuning for Dummies page’ that shows how very important the plate weights are too.

Coupling Frequencies

    To get more consistent results, especially helpful for beginners, the other change to traditional practice the Mr. Kreit introduces is measuring and setting what he calls the Coupling Frequencies.

  There are  two Coupling Frequencies are the tap tones or resonant frequencies measured when

    1) just the back plate is glued onto the bouts (or garland) and without the neck attached,      and then

    2) just the belly is glued onto the the bouts (or garland), again without the neck.

        These are easily and quickly measured, but do require that one of the plates is first temporarily glued (using diluted weak glue and cigarette papers!) to the bouts or garland, and then removed before the other plate is glued to the garland.

     This puts an important intermediate step between setting the tap tones of the pates and then setting the difference between the coupling frequencies of back and belly to about 25 Hz, as shown in the important chart on the right. Click on it - it is a .pdf file.

 This does makes the violin body resonant mode frequencies much more predictable.

   You will also find a model that predicts these key violin body frequencies, that have a major effect on what it sounds and plays like, on the ‘Plate Tuning 4 Dummies’ page.

    So using this ‘hierarchy’ of relationships(right) for a violin made from scratch - started from blocks of wood - you can measure the 19 different frequencies of the individual parts and then at the end measure the final body-mode frequencies of the finished violin that have been predicted.

   So the instrument ends up with the key body resonances where you want them. The chart I sometimes use to do this for violins is here on the right - click on it.

Plate weight

   Does it matter if violin plates are heavy even though they are tuned to the right Mode 2 and 5 resonant (tap tone) frequencies?

    Well, yes it does, and a lot. The weight, or rather the lightness of each plate is a measure of its quality, providing that it has the right tap tones and low losses when it vibrates. A light plate with the right arching and thicknessing on good wood has less wood for the bow and strings to move: it will respond more quickly and give out more sound energy.

   If you have a look at the page on ‘Plate tuning 4 dummies’ I show you how to make the best of the wood or plates you have to make a violin that will sound very good indeed, but there is no substitute for buying the best low density stiff wood you can afford! 

   ‘Ordinary’ wood will make a good violin (as the Chinese student violins now show!) provided you get the plate tap tones right!