Importance of tuning tonebars and f holes

[ecklesweb]

I've built a very simple flattop A-style mandolin. #A friend gave me the Siminoff book, so I'm thinking about diving into a carved-top F-style. #One of the questions I have is whether all that business about tuning the tone bars and the f-holes is crucial. #For one thing, I'm not sure I follow that section real well. #For another, I don't think I have the equipment to actually tap tune the top to begin with. #

So, if I'm basically planning on skipping that step, am I better off not even starting? #Or will I be able to get away with it and come out with a decent instrument? #I did a quick search and didn't come up with any definitive answers. #(perhaps because there are none...)

If it is crucial, what piece of equipment should I look at procuring/begging/borrowing to do the tap-tuning?

Thanks,

Jay

[sunburst]

The consensus seems to be (and my opinion is) it ain't too important. There is not really muich you can do toward tuning to specific notes, and nobody seems to be able to relate free plate resonances or Helmholtz to anything in the completed instrument. I think that's why it was left so vague in the book.
If you want to experiment and record what notes you have, there are programs available for your computer. I don't know much about them because I have an old tube Strobocon and havent needed one, but someone will probably chime in with some info.

[labraid]

My opinion is that soundbox cavity volume remaining the same, the dominant tap tone you'll get is a direct reflection of the stiffness/strength of the top or back. It may or may not have a huge effect on final tone being a bit or a lot off the "standard", but you will get consistency if nothing else. You could probably "rough it" (following Siminoff's recommendations for graduation and tone-bar height as per the pictures/diagrams) and do exceedingly well. Remember, the first Loar's were themselves a new idea, a new recipe. Who guided him???Recipes can differ and still end up tasting better with a bit of intuition in the mix.
Which reminds me, "Worrying will spoil your brew more than any mishaps. Relax, have a homebrew" -Charlie Papazian
http://www.mandolincafe.net/iB_html/non-cgi/emoticons/biggrin.gif

Good luck!
Brian

[Chris Baird]

Unless you are a phyicist or really into math and the study of acoustics I doubt measuring resonances of any sort will help you out. It gets very complicated and so far those who have had some success with it report that it is only a small part of their whole building process. I still devote some time myself to various tests but only out of curiosity more than an expectation that I will find a magic formula for building great instruments. There are various shareware and freeware fourier transform programs that will take a .wav that you record with your computer and break it down into all it's parts; fundamental and partial with amplitude. Search for freeware FFT etc..
My advice though is to just build and take note of everything you can using the senses you've got. Bend, flex, tap and listen to the tap quality, etc.. Change things around as you build and use your ear to quantify the changes.

[labraid]

To add $.02 to Chris' post, Stradivari and many others had all those computer programs built into their head via the five senses. "Is there anything too wonderful for God?" Indeed no. Practice and desire make, well, pretty darn close to near almost perfect http://www.mandolincafe.net/iB_html/non-cgi/emoticons/biggrin.gif

[Dave Cohen]

There have been numerous threads on this subject before. More importantly, this subject has played out in the violin world before. In a nutshell, Harvard physicist Frederick Saunders was very interested in the physics of the violin. Along with Carleen Hutchins, he eventually founded the Catgut Acoustical Society. Carleen was a strong proponent of free plate tuning, and probably remains so even now (though with some reservations). However, in the mid 1990s, two investigators put a damper on the free plate tuning concept. Both Schleske and Atwood independently attempted to follow the "tuned" free plate modes into assembled violins. To make a long story less long, they couldn't do it. The violins with plates which were not "tuned" had about the same corpus mode frequencies as the violins with "tuned" plates. Now, this doesn't mean that there is nothing at all to free plate tuning, it just means that we don't know much about whatever there is to it. With hindsight, it seems clear that the corpus modes of an instrument shaped box are completely different than the modes of free plates. The modes of free plates are more like beam modes.

Siminoff's "tuning" is another story altogether. It is well known in the physics community that the normal mode shapes and frequencies of a plate are independent of how or where the plate is excited. The only exception to that is if you happen to strike the plate at the location of a node for a particular mode, in which case that mode will not occur, i.e., will not be excited, while all of the other modes will occur. So it doesn't make much physical sense to think that each "tone bar" can be "tuned" independently of the other. They can't, and they aren't. I suppose that Siminoff could make the case that he is tuning the entire plate from the vantage point of exciting it at each tone bar, but he will have to come up with a much more Newtonian explanation to convince me to take a second look.

John, it is not true that nobody has related the Helmholtz (air) mode to anything in a completed instrument. It is well known in both bowed instruments and lute family instruments (mainly guitars) that the fundamental body resonance - the (0,0) mode or T1 or C1 mode - is a doublet or triplet which should bracket the frequency of the Helmholtz air resonance in order to have efficient sound radiation in the lower frequency range of the instrument. There is scads of literature on this for violins and guitars, and now of course, a couple of Cohen & Rossing papers on this for the mandolin as well. Shoot, there are even a few papers on this for the P'ip'a and the erhu as well.

[Brookside]

I don't think this would come up as often were in not for Siminoff. I'm curious if anyone knows the source of Siminoff's "instruction" on this subject. It is very specific. Does he profess to have developed this specific method or was he taught by another? Whatever the case, build your mandolin. If you want more information on the subject, run a search of this forum for "tap tuning." You will find plenty of information.

[crawdad]

I tried to follow the Siminoff tap tuning method using my ears to get a full step between the tone bars when tapped. The closest I could get was a step and a half. He even seems to run into the same thing--get as close as you can seems to be the Siminoff mantra. Does it matter? After I build a dozen or so, I might have more insight, but not yet.

I'm carving a spruce top right now, and this particular piece of wood seems to be much more dense than the first one I carved. I think that will facor into a totally different sounding top, regardless of the shaping of the tonebars. My guess is to get as close as you can and relax after that. I also guess that carving a top with good graduations based on the Loar model, whateer that might be, is probably a good way to go.

I do know that the tonebars add strength to the top and help to focus the vibrations of the string energy as it is transferrred. So do them the best you can, but don't lose sleep over it. Since every piece of wood is different and every top is at least slightly different, none of them are going to sound the same anyway.

[Dave Cohen]

So what exactly do you mean by "focus the vibrations of the string energy as it is transferred"?

What the "tone bars" do is stiffen the plate primarily along the longitudinal direction, i.e., along the direction of the grain. That stiffening has the effect of raising the frequencies of the modes which involve bending along the direction of the grain (e.g., (0,1), (0,2), (1,1), etc), while the modes which involve cross-grain bending (e.g., (1,0), (2,0), etc.,) occur at lower frequencies.

[labraid]

I am curious, when people do these testings, do they do them through a mock bridge, ie, something where the vibrations orginate from and which places the same amount of string pressure as would a bridge... to simulate a real working situation?

[sunburst]

Dave, thanks for the Helmholtz correction.
Have you guys tested a "control" top with no bracing (bars, whatever) to see what does or doesn't happen?

[Dave Cohen]

I do holography on mandolins in playing condition, i.e., strings at tension, damped w/ a small piece of foam between the strings and the fingerboard. A small NdFeB magnet is placed on the bridge saddle w/ dental wax, then driven w/ a coil by an ac signal. At the same time, the laser interferometer is generating holograms in real time.

The problem w/ your reasoning is that a plate without braces would NOT vibrate more locally. The mode shapes would still cover the entire plate, i.e., they would be "global". That is even true for membranes, i.e., drum heads or banjo heads. Without braces, the mode frequencies would be lower, NOT higher. Braces do not "distribute vibration". They stiffen the plates, consequently raising normal mode frequencies. The scientific understanding of bass/treble balance in an instrument is not as simple as stated above, and of course is not even fully understood.

I guess that what I get annoyed with over time is the tendency for some luthiers to "invent" their own physics. Lutherie is a curious mix of art and science. There is a subset of luthiers who are very technically aware. Other more artistically oriented luthiers seem to feel obligated to couch their observations in scientific terminology without bothering to do the homework to see whether or not their terminology is nonsense. Imo, their observations are perfectly valid. I just wish that they would state those observations in artistic or purely empirical terms, rather than feeling obligated to invent fictitious physics. When fictitious physics is presented over public forums as being obvious and conventional wisdom, the left-brain luthiers are put in the position of having to refute the "conventional wisdom", which is not wisdom at all. Believe me, it is an awkward position to be in. If you just stay out of it, the fictitious wisdom can become established dogma; If you say something, you are often seen as a curmudgeon or worse.

[oldwave maker]

Thanks guys, always a fascinating thread, reminds me of looking slightly toward the sun to see the reflection of your optical nerve on yer eyeball, the more you try to look right at it the less you actually see it, hmmm, more metabiophysics?
My son won the utah state mando championship last summer, on tone more than flash, with my first siminoff clone f5 made in '93. While I am eternally indebted to Roger for overall inspiration and guiding me thru my first few mandolins, Ive always wondered: who actually has one of his, who plays one of his, how consistent are they, do they sing way up the e string, growl like a maddog on the g string, with a chop that sounds like beating on a hollow log with a louisville slugger? If Kemnitzer or Gilchrist wrote a book on top tuning, I'd buy it in a second, cuz the proof is in the pudding, I really like all the results of their art/science Ive had the opportunity to play. I attended the GAL convention a few years ago and listened to someone expound at length on building mandotone till I found out he had not actually built one yet, probably wouldnt buy his book unless there were lots of nice photos of nekkid wimmin at the workbench.....
bill, always searching for mo' betta' top wood

[labraid]

That's unfair that the only ones who can say something on the subject are the ones with hologram-majigers and interferometers. Learning is a process of making errors and having them corrected by those who know better. A process of discussion. If I say something you don't agree with, then say it how you've seen it, accept that others are not always going to be born with all your experience, and be happy they aren't, or you wouldn't have anyone to share your knowledge with. Wouldn't life be boring if we all knew it all and so couldn't offer advice in our area of expertise?

[sunburst]

That's unfair that the only ones who can say something on the subject are the ones with hologram-majigers and interferometers.
With all due respect to all involved, Dave didn't say nobody else but physics guys had anything to say. He said our observations are valid, but we need to remember that they are just that. Observations.
I have a scientific background, not to the extent of Dave, just a BS, but I understand the basics of the scientific method, and I can understand his stance of being uncomfortable when we put our observations in incorrect scientific terms. Anecdotes are not science and shouldn't be stated as such, but they are valid observations none the less.

Oh, and speculation is speculation. Nothing wrong with that either. It's almost the same thing as a hypothesis, which is the idea at the beginning of an experiment. It's not the same as a conclusion or even a theory. Let's just not call things what they ain't.

[mandough]

No one has addressed the F-hole part of the question.
I think that this is a very crucial part of the ending sound of the mandolin.
Siminoff is very vague in his book about this subject because he doesn't really state what your goal should be.
I guess he trusts that we all have a great "ear" for hearing the best tone.
If you put a small rubber grommet (like one of the big Radio Shack grommets that you didn't use after you put the small ones one your strings) you can change the sound of your mandolin greatly. I suppose that this means that the size of your F-holes is crucial to getting the "best" sound out of your mandolin.
Just an observation, no science here.

[labraid]

Where does the rubber grommet go?

[P Josey]

I usually don't get into these discussions but I do have something to say . It's fine to go on with scientific jargon around the acoustics of musical instruments. It's also fine to say you don't tune to a specific note, you just tap and flex until you hear the sound your looking for. I think it was Chris Baird that started a thread a while back trying to pin down some concrete info on tap tuning but he didn't get anywhere with it. At least Siminoff gives the less experienced a starting point when it comes to tap tuning and voicing an instrument. So although some may consider it unimportant, to the less experienced, I think it may be all there is to go on. From there, you can start to develope an ear for the sound you're looking for. Paul Josey

[Brookside]

As usual, a very colorful discussion on the subject. I posed the same question a few weeks ago in regards to "where are all the Siminoff mandos?" One guy responded and said, "I've played one, years ago, not bad." I do wish some of you other builders with great reps and a bunch of quality instruments circulating would write up a builders guide for newbies. Anyone listning?

As for "the f-hole part" it was addressed in the past, I believe by Dave. If I remember corretly that thread was what caused me to stop bothering with "tuning the f-holes" per Siminoff's instructions. I cut them to spec size and shape, smooth the edges and move on. When you see various f-hole designs that are not traditional, do you figure the luthier figured the precise amount of wood removal to the square millimeter in order to "tune" them. I don't think so.

I don't have a scientific background for the most part. My job is in fiber-optics. There is endless theory that applies to this line of work but I am just an installer. I put a good splice or connector on the media and run a signal through it. A meter or OTDR will show me that a particular splice or connector is exhibiting a loss of .05 Db more than another splice or connector. The bottem line is that the end user will never be able to tell the difference between the two in terms of the performance. Make no mistake, those who work the theory end of it are essential in long term improvement in this technology. They develop better methods for connecting and splicing and lower the overall loss of the media. My role in fiber-optics is the same as my role in mandolin building. That is to build as best I can while leaving the extensive theory to the experts. As they learn and (hopefully) share their knowledge of the science behind it all, I will apply and benefit. Once again, if any of you folks would write up a physics 101 guide for newbies, I'm sure there are many of us who would benefit from it.

[Yonkle]

I went through is topic too while building #3. I took someones advise here and just went by the numbers. Cut the F holes to the specs on the Siminoff blueprint and shaped the tone bars to the specs, sanded them and went on. Number three sounds great, it is only 6 weeks old and is very loud and has a good chop. I played in a small jam last week, one fellow had a Weber Yellowstone and the other had a 1913 Gibson A2. Mine sounded real close to the Weber, I played the gibson a while and it had a very different sound, which it should being a oval hole and being very old. Anyway I think if one is building professionally after building so many there is something to be said about tap tuning, if you are only doing one or two for your own pleasure, just go by the specs and don't worry about it. JD

[sunburst]

I do wish some of you other builders with great reps and a bunch of quality instruments circulating would write up a builders guide for newbies. Anyone listning?
That thought crossed my mind many years ago when I thought I new something about mandolins.

I'm not a builder with a great rep and a bunch of quality instruments circulating, but I saw the need for a guide with a different approach and thought I might have the knowledge to write it someday. I now realize what a pretentious thought that was! The more I learn about mandolins the less I know about them.

I still think the need is there, and maybe there is someone out there willing and knowledgable enough to write it. It would be quite a job!

[Dave Cohen]

Sunburst (John), thanks for the clarification. You said it well. I never wanted to silence anyone or put them down; it would just be nice if folks didn't invent Star Trek science and then insist that it must be true. But as for observations on tone and what is done to produce a certain tone, etc., all who have those observations are deserving of being heard.

Now for the f-hole part of the discussion. If you shave the edges of the f-holes as Siminoff suggested, you will hardly change the frequency of the Helmholtz resonance at all. We are talking a few tenths of a Hz here. Otoh, if you change the total soundhole area by about 30%, you will only get about a 7% increase in the Helmholtz resonance frequency. Now, 30% is a whopping change; you ain't gonna get there by shaving the edges of the soundholes. It is much more practical and accessible for a luthier to adjust the plate frequencies by removing wood, thereby adjusting the overall stiffness of the plate(s). There has been a series of articles in American Lutherie on how Don MacRostie accomplishes that and teaches it. He will also be demonstrating it at the GAL convention this summer.

[crawdad]

So what exactly do you mean by "focus the vibrations of the string energy as it is transferred"?

What the "tone bars" do is stiffen the plate primarily along the longitudinal direction, i.e., along the direction of the grain. #That stiffening has the effect of raising the frequencies of the modes which involve bending along the direction of the grain (e.g., (0,1), (0,2), (1,1), etc), while the modes which involve cross-grain bending (e.g., (1,0), (2,0), etc.,) occur at lower frequencies.
Hey Dave...yeah, thats pretty ambiguous, LOL....sorry. I want to explain myself, but I'm afraid I'll probably be digging myself in a deeper hole. I think "focus" is the wrong word. All I was trying to say is that the tonebars affect the resonanant frequencies of the top, which will act with the string vibration to produce sound....and that resonant frequency changes depending on how the tonebars are carved and tuned.

If we had a top and could change tonebar sets, we could try different ones until we found a tone that had a set of fundamentals and overtones that we liked the best. Oh to have a perfect world...

Maybe I'm still making no sense and maybe I'm inventing my own physics, but thats as well as I can explain it from my firsthand experience. Carry on! I promise to refrain from anything even BORDERING on physics in the future, LOL! No offense meant and none taken.

[RI Jim]

I'm with Mr. Bussman, when Nugget is ready to re-tire and decides to ( Hopefully ) put the pen to paper and tell people how to REALLY do it, THAT will be the book to own.

Tap tuning = tap the top and back, if she rings like a bell...... it's tuned !! < G >

Jim http://www.mandolincafe.net/iB_html/non-cgi/emoticons/biggrin.gif