Simeon Chambers (in Colorado, USA) has a good range of wood at reasonable prices and plate thickness maps for sale too. He suggests the light Englemann spruce for bellies, with a density (specific gravity) of 0.34 to 0.38, which is much less than than normal European spruce at 0.45, but European makers seem to prefer Bosnian Spruce.
To get a violin to sound good you need to get the 6 key resonances below 600 Hz in the right place and these resonances need to be in ‘harmony’ with each other.
1) The air inside the instrument resonates through the f-holes, so it has to the right internal air volume and the f-holes need to be the right size or area. This gives strength to the G-string’s sound. (This is the Helmholtz resonance)
2) The air column along the length between the end blocks resonates rather like a church organ, so the body needs to be the right length,
3) the arching and channel around the violin needs to be the right shape, and
4) the tap tones or speed of sound along and across the top (belly) and back plates needs to be within tight limits. These give strength and quality to the A-string’s sound.
5) The plates need to be as light as you can make them for sound volume - but with tap tones not too low (see 4) above.
6) the bridge and sound-post must be fitted correctly so the violin talks, and so the higher frequencies, all of them, and there are lot above 600 Hz, can come out.
There is a lot to get right.
Theory: Dr. Nigel Harris and Patrick Kreit
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 air volume, f-hole area, arching, body length, sound-post and bridge must all be right too.
About five years ago I came across an article by Dr. Nigel Harris (interviewed here!) that seemed to be the next step in the elusive connection between the tap tones of a violin’s plates, its playability (the violin’s is ease of bowing), and a real quality and depth of tone. In addition, as Dr. Harris puts it, it can make a given tone reproducible, violin to violin.
I did develop an elaborate theory over the last few years based on combining Dr. Harris’ and Carleen Hutchins work, but it dawned on me a few months 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 4 similar (ideally identical) violins:-
1) with a heavy front and heavy back plate,
2) with a heavy front and light back,
3) with a light front and heavy back, and finally
4) with a light front and light back plates,
and then see what the differences are.
The criteria for the quality of the resulting violins would be based on
a) where the key 6 resonances below 600 Hz fall, and
b) what the 2 violins are like to play: their tone and response under the bow.
Fortunately, with practice, the key body resonances 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+.
For 1), with 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 maple back I made) showed that the weight of the belly and back plates has almost no measurable 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) and when belly and back are heavy only the Mode 5 and Mode 2 plate frequencies mattered. 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.
2) For a violin with a heavy front and light back I had mended and tuned the plates on an old Hopf copy from about 1810/1820, which gave very good results - but it isn’t Strad. model of course!
3) I have yet to find a violin with a light front and heavy back to work on, so there is still plenty of work to do........... and for ....
4), a good quality violin with light plates?
Well fortunately, Patrick Kreit (on the right in the photo below) has published “The Sound of Stradivari” (there is also his new site about the book here).
I came across this rather book (costing € 285) in 2010. Mr. Kreit links the Mode 5 frequencies of the violin’s plates to the resonant modes of the final violin body, step by step. He has done 10 to 20 years work in exploring the relationships between violin plate’s resonances (with Mode 2 set to half Mode 5) and the 6 key body resonances: see the ‘Resonances of the Violin body’ page. He has found a method for consistently getting the lightest possible plates .... so I did not need to make a Strad-model violin with very low plate weights to compare it with: all the data is in his book.
Limitations to Dr. Harris’ work have shown up too in Jo Curtin’s work, published in The Strad Journal: vide this page revealed by his his article on Strads. The effects of gluing each plate to the stiff bouts seems to dominate!
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 air volume, f-hole area, arching, body length, sound-post and bridge must all be right too.
My findings so far are that Carleen Hutchins 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 will turn out sounding good!
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 withoiut the neck.
These are easily and quickly measured, but do require that one of the plates is first temporarily glued (using very weak glue and cigarette papers!) to the bouts or garland, and then removed before the other plate is then 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 figure right (click on it - it is a .pdf file).
So for a violin made from scratch, that is started from blocks of wood, I can measure the 19 different frequencies of the individual parts and then also the final body-mode frequencies of finished violin. So the instrument ends up with the key body resonances just where I want them.
The chart I use to do this now for all violins is here on the right. It is particularly good for violins made starting from blocks of wood. (Again, click on it - it is a .pdf file that can be saved): -
So 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, a lot. The weight, or rather the lack of weight or 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, then there is less wood for the bow and strings to move: it will respond more quickly and give out more sound energy.
So, if you are making a violin you will to need to buy the best wood you can afford. However, ordinary wood will make a good violin (as the Chinese student violins now show!) provided you get the plate tap tones right!
Quick results: Plate Tuning for Dummies!
There is a page called “Plate Tuning 4 Dummies” for those who want quick results and simple rules of thumb to make a good fiddle first time round, but you really need to check and adjust the tap tones of the partly assembled and even the fully assembled instrument to get a really good one. There are no short cuts, because every piece of wood is different.
I have 8 or 10 beautiful and well-made violins by amateurs that look wonderful on the outside, but play like the old cheap school fiddles - simply because they did not have their plates tuned at all!
So have a a glance here for the basics: but you’ll still need to know how to hear and or record a tap tone on the “How to Tune Plates” page of course!
What this is all about? Make a $150 violin sound like a $3000 violin
So this web site is all about just how to measure tap tones to help you make a new violin, or to modify an existing and poor-sounding $100 factory fiddle to get it to play and sound like a $2000 violin.
So have a look at the various pages here. In particular, have a look at how to easily measure tap tones, and how to use them to get matching front and plates even when using less than the best spruce and maple. I’ll show too the various stages of how I modified some constructionally challenged instruments.
You can’t do much damage to a £40 ($60) violin: at worst it’s £40 of experience. But Warning: but do not do this on your Concert Strad.
Feedback: tell me what you think, and tell me your experiences.
Let me know what you think of this site and its contents: violin plate tuning seems to evoke strong emotions in luthiers ...... so email me now at email@example.com ! It’s all work in progress, so I’ll include your comments, but no promises though.
Footnote ** : F# is 370 Hz, F (natural) is 349.2 Hz, and E is 329.6 Hz. The reference here is to Ed. Heron-Allen’s book on violin making of 1885-6. Believe it or not he refers to Modes 2 and 5 and ‘nodal lines’ on p.133, and tells the reader how to make them visible using sand and a bow! Yes, that’s from 125 years ago.
Footnote 1) Many authors (Hutchins, Molin, Moral, Schleske) use the terms “eigenmodes” or eigenfrequencies”: they are just body resonances of the violin corpus, in part or finished state.
Footnote 2): In particular the B1-, B1+ and CBR body resonances. Since the two coupling frequencies are present on the finished violin, they are in fact “eigenmodes” or “eigenfrequencies” 1 of the whole, finished violin. So thay can be adjusted or set at the intermediate stage during the building of a violin, i.e. with just one plate at a time glued to the bouts or garland. The two Coupling frequencies then control and set the key B1-, B1+ and the CBR (C2) body resonances.