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 Last updated  12th.   May 2012  (C)   Copyright          platetuning.org

  This site available in all the major world languages here at Google translation in  French,  Spanish,  German or Greek   ....

So, what is this site for?

This site is for people who are making a violin or viola, and also for those who want to modify a low-cost and poor-sounding instrument to dramatically improve its tone and playability.

 I’m not trying to sell you anything here. And there are no ads or malware. Really. I believe strongly in the ‘Wiki’ idea: I feel a need to communicate what I know, so that’s what I want to do for other amateurs. What I ask in return is to hear your story, so please comment in my blog, or better  mail me back to let me know what you’ve learned in fiddle making!

The parts of a violin

  First, what are the parts making up a violin? Have a look at Hans Johannsson’s site: there’s good stuff on the construction of a violin.  You can see the front and back ‘plates’ in his diagram left - click on it.

Tap Tones for the front and back of violins.

The two pieces of wood that make up he front and back of a violin are called ‘plates’ seen on the left.

       If you open up a violin, or you are making one from scratch you can change (which means reduce) the tap-tone frequencies of these plates using a tiny thumb-plane and scraper by  removing wood from the inside of them. You can measure these tap tones as you go by using a microphone and your home computer so that the violin (or viola) will sound really good. As well as thumb plane and scraper you’ll need some kitchen scales and a thickness gauge. You can then be confident that your first or your next fiddle will sound excellent! Or perhaps you could also improve the tone quality of low-cost, poor sounding violins as I do!

This isn’t my work really. It’s using, summarising and building on the years of work others, the great names have done over the last 60 and more years. I have no problem with standing on the shoulders of others. I’m an experimental researcher by inclination and training: ‘try it!’ I say. And I love reading and learning what others have written and I hope you benefit.

Good tone: the search for the grail.

At the heart of getting good tone from a violin is matching the tap tones of front and back plates. The plates’ tap tones are a measure of the key properties of the plates. What tap tones do is show up the quality of the wood itself, especially the spruce of the front or belly. So don’t just use any old wood. Use good old wood.

By setting these tap tones to chosen frequencies, as well as matching them front and back, almost any factory violin can have its tone dramatically improved, whatever wood it is made from. Have a look at the example violins (and violas) on the ‘Violin viola examples’ ref. page.   For interest I’ve also included pictures of what the best makers did over 300 years ago with some pictures of the outstanding instruments at the Ashmolean Museum, Oxford, UK. Do see them in person if you can.

The tap-tone method outlined on this website allows you to choose the tone you get too. It could be a ‘student’ tone for easier bowing, or perhaps you want a ‘solo’ instrument tone with harder bowing, but very powerful, and suited to real solo work.

My personal preference is for ‘chamber’ and ‘orchestral’ tone instruments midway between the two: easy to bow, and flexible in use, suited to an Irish pub session, a quartet or in a symphony orchestra.

The key to this choice of tones lies in the key violin body resonances or modes, and there’s more details on those modes on this page here, but that is definitely running before we can crawl. Get the plate tap tones right and the assembled body resonances, with some skill and craftsmanship, come out right!

Limitations: you need craftsmanship too

This however is not a cure to all human suffering. Much or most of a violin’s quality of sound derives from just ‘good practice’ in its making. There is no substitute for proper, patient, practiced craftsmanship and artistry in the making and modification of an instrument. It should be, it must be a work of art!  I cannot begin to teach any of that. I can only help with some of the science and engineering aspects. Go to a craftsman for craftsmanship, and set aside some years to do it.

Tuning the plates

 Plate tuning can help make your first or your fiftieth violin a good instrument - a fine reward for 10’s of hours of work. And it is not at all difficult. I personally mostly use this method to improve the tone and playability of factory-made or damaged fiddles, such as ones with bad soundpost cracks.

Significantly, I have found a way of quickly measuring Mode 2 and Mode 5 frequencies of violin backs and the back’s weight, without removing the back from the bouts (sides and blocks). So using a short knife and warm isopropyl alcohol  / water I only remove the front and fingerboard to measure and work on the inside of the back to set up the back’s tap tones (Modes 2 and 5) and Mode 5 (ring) tone. Then I modify the front to match it.

The Mode 5 of a back plate is reduced by about 15% in the bouts, as can be seen in John E. McLennan’s paper (UNSW) on page 5 & 6 . However, usually Mode 5 divides into 2 frequencies up to 40 Hz apart, one either side of 300Hz. So I can get a good estimate of a back plate’s Mode 5 while it is in the bouts ands still attached to the neck. I do this by ‘combining’ these 2 ‘modified Mode 5’ frequencies measured with the back plate still in the bouts using a ‘weighted average’ method: a chart to do this easily is shown here on the right. Just click on it and print it out. The instructions are at the top.

Mode 2 of a back plate when in the bouts is only slightly increased, but the neck with no fingerboard unfortunately has a resonant frequency at almost exactly the same frequency, so we have to move the neck’s resonance out of the way to measure it. Get in touch with me if you want to know more.

If a back is good and with specially resonant tap tones, carving a brand new spruce front can also give you remarkable results: but you have to start with good seasoned spruce for the belly though!

Arching and thicknesses

If you want to know what arching and thicknesses to use for the plates, have a look at this page.

I have included 2 figures that show how to thin plates to get Modes 2 and 5 where you want them. This data is from  Acoustics for Violin Makers by Erik Jansson in  “Chapter V: Vibration Properties of the Wood and Tuning of Violin Plates”, and here is just  page 25 extracted from it, with a scheme to gradually reduce thicknesses of plates in an appropriate way while keeping Modes 2 and 5 under control.         This series of papers by Erik Jansson is a key reference work on acoustics and the violin: and it’s free! He used to work with Carleen M Hutchins (CAS) and really knows his stuff. Have a look on the links page too.

History: let’s start at the beginning

 Every journey begins with but a single step, and every organisation begins with a single member. That’s me. My committee meetings always run without a hitch.

   I’ve always wanted a Stradivarius or Guarnerius violin, but somehow I can’t seem to muster that first £ million. I played a Guarnerius violin once, and it spoiled me: how could I, that bowing arm be making that fabulous sound? That sound, that’s  a bit like a professional soloist on a CD?  Well, with all the arrogance I could muster as a qualified engineer, I decided if I couldn’t buy one, I’d have to make one. And of course, I know that as soon as I get a Strad then my amateur scratchings will be instantly transformed into something truly wonderful ......

  I am now retired, with violin repair and violin making as a (fanatical) hobby.  I can spend time building and rebuilding violins and violas as experiments to test out ‘plate tuning theories’ as the fancy takes me. I have no commercial interests, and that gives me a big advantage: a fiddle shop just cannot afford to do that!

A rationale, and Carleen M Hutchins.

    Over the years, while trying to make some awful violins sound better, I needed a rationale to this mending and tinkering. My long-suffering wife bought me the collected works of the CAS (Catgut Acoustical Society) for Christmas 6 years ago.  A remarkably lady, Carleen Maley Hutchins (photo right) co-founded this Catgut Acoustical Society (CAS) nearly 50 years ago, and I remember her first article well: my mum showed it to me in the early 60’s when it was printed in Scientific American , Nov 1962. You may be able to get back-copies if you do a web search.  A later article by her I think in 1982 can be found here on a Russian website, which I’ve put into a .pdf file here. The excitement of that approach stayed with me. Carleen died in Aug ‘09 at the grand age of 98, and her obituary was published in the LA Times. What a lady!

    Traditionally, violin makers ‘tune’ the front and back plates around an ‘F’ to ‘F sharp’ tap tone**. Tap-tone methods has been around for well over a hundred years (see footnote) and probably very much longer. Unfortunately factory-made fiddles, all that many of us can afford, have never even heard of ‘tap tones’ or even suffered much care in manufacture. Indeed many of these fiddles have so much wood in the back that if burned they could heat a small home for an evening.

Quick and free measurement with the home computer

     What has changed over the last 10 to 20 years is that the ubiquitous home computer (right), used with a cheap microphone, has made available to us methods for measuring tap tone and violin body resonance frequencies very, very quickly. It takes me a minute or so to measure the tap tones of a violin plate. Carleen would need perhaps an hour, and Signor Antonio Stradivari? Well, he needed a very well trained ear and maybe a a ‘standard’ wooden rod or mono-cord to tap for comparison.  A good ear helps these days, but is not essential.

   At first I found that Carleen’s methods of adjusting the tap tones of front and back to an octave (1:2 ratio of Modes 2 and 5 frequencies in both) just did not seem to produce really good fiddles: but they were better. I think it’s because the wood for factory fiddles, especially the fronts, is not good, low density, prime-choice wood and you have to strip the violin right down to its parts!

Makers can pay as much for the wood as some might pay for a violin outfit.  Try Luscombe Violins in the USA, or  Touchstone Tonewoods in the UK.  Simeon Chambers (in Colorado) 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.

Theory: Dr. Nigel Harris and Patrick Kreit

          About five years ago I came across an article by Dr. Nigel Harris 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.

 Dr. Harris (right) who sells some seriously good, pricey violins at Harris & Sheldon (violin.co.uk)  links the plates’ Mode 5 (called the ring tone),   Mode 2 (the ‘X’ Mode), and the weight of the plates into what he calls each plates’ ‘Stiffness Figure’. His work on 1000 + violins shows that if the front and backs have a similar ‘stiffness’ then a good fiddle will result.

       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+.

Results

   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 (left) has published “The Sound of Stradivari” (and there is also his new site about the book here).  I came across this rather costly book (€ 285) last year. 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!

Simple theory

    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 then

    2) just the belly is glued onto the the bouts (or garland).

    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).

This makes very important  violin body resonant mode frequencies much more predictable².

So for a violin made from scratch, that is started from blocks of wood, I can measure 19 different frequencies of the parts and then the final body-mode frequencies of finished violin so the instrument ends up with the key resonances just where I want them. The chart I use to do this now is here on the right:

 Plate weight

 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 in each plate is a measure of its quality, providing it has low losses when it vibrates. A light plate has the right arching and thicknessing on good wood, and 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.

 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 about 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 ! It’s all work in progress, so I’ll include your comments, but no promises though.

So please  Email me!

PS:  Amusingly, this website is also available in the Russian language.  It is also available in all  the major world languages here at Google translation in   French,  Spanish,  German or Greek   ....

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.