Tap tuning using a guitar tuner?

[StuartGold]

I was reading the Siminoff book and he was discussing using a fairly sophisticated electronic set up to dial in the final tones for the back and top before they are joined. Is it possible to do this using a simple clip-on guitar tuner? If so, is it better to use vibration mode or microphone mode? In the IV kit that I am planning to build, the top is already attached to the rim, the book mentions that there are different tones for the top by itself and the top attached to the rim. This suggests that the extra bulk of the rim affects the tone of the top. Not surprising in something that uses such narrow tolerances. If it works to set the tone using a guitar tuner in vibration mode, wouldn't the extra weight/bulk of the tuner itself, change the tone? I'm a bit of a newbie to this process. I've built a guitar before and just kind of guessed while I was thinning the top. I lucked into a very nice sounding instrument. I think that the mandolin is another animal all together and I need to be a bit more anal about making sure that the thicknesses and tone are as exact as I can make them.

[Marty Jacobson]

Ok.... I've been doing a ton of tap tuning experiments over the last few weeks. Hopefully I don't lead you astray, but this is how my current understanding sits.

First of all, Siminoff makes tap tuning look very easy and straightforward in his demonstrations. But in practice, little things can change the tap tone pretty significantly. So as you are starting out, the "quantifiable" tap tone which could be measured by a strobe tuner can vary wildly depending on some of the following things:
- where you tap the plate / tone bar
- how hard you tap
- what you tap with
- what angle you tap at
- what you are thinking
- what you had for breakfast
It's just a huge set of variables, and it takes a lot of practice and feeling around in the dark before you weed them out.

Remember that Siminoff is a production guy. His method of tap tuning is really more about repeating an instrument that you know to be good than a useful way to take a shortcut to a great sounding instrument. It's very valuable and I've learned a lot from him, but this great tone doesn't come from reaching magic notes, it comes from making a good instrument, knowing what the tap tones were, and then refining that into a new instrument as you build it.
If you are tap tuning to "reach a magic note", that doesn't really do you that much good. Instead, you should be tap tuning to reach a balance of flexibility, stiffness, and "liveliness" in the top which inspires confidence in your mind that the instrument will sound good.

If you take it too literally, it can really make you tear your hair out. Say you are using StroboSoft to analyze the tap tones of the tone bars on a plate. At some stages of the tuning process, the fundamental of the braces will be so far above the "target range" (say, 7th octave A when you want to get a 4th octave G#) that it will be indistinguishable from the other random overtones. So you can remove some material, tap again, etc. As you do this, there may be a natural peak which is a result of the whole coupled top/tone bar/rim assembly which is a deceivingly pure peak at something reasonable like 530hz. But after carving the tone bars completely away, you might only be able to affect that 530 hz tone down to 505hz. That's why it can be nice to use Audacity (see below) because you can see the whole spectrum, and see what are stationary peaks like your tap hammer hitting the wood versus the actual vibration of the plate.

So anyway, I would caution against treating Siminoff's method religiously. It would be nice if you could just follow the process he outlines and get great tone. But I don't think anyone's found that to be the case. Even once you get to the point that it feels like you are doing that, it's the result of trial and error.

I think one thing that is particularly useful that Siminoff teaches (at least the way I understand it) is that of the harmonic relationships of parts in the instrument.

You cannot use a guitar tuner. They are not precise enough or quick enough to respond to the short impulse a tap tone makes. Using a compressor, maybe. But you're better off with the demo of Strobosoft, or better yet, using the FFT Spectrum analyzer tool which comes with Audacity.
This is a now-classic article on the subject:
http://www.platetuning.org/html/how_to_tune_plates.html

You can tune your plates in or out of a rim. In a rim, it makes it easier to get a repeatable measurement, but ONLY if the rim mates very truly to the underside of the plate. Also, even the most minute (.01mm) gap between a surrogate rim fixture and the back or top plate will cause chaotic buzzing, and throw the whole measurement off. Double-stick tape the plate down for a quick and dirty fixture if you want to see what it should sound like.
However, free plates ring much nicer and it's much easier to hear what's actually going on. Hold the plate about 20% in from the edge somewhere inside the rim. This will allow you to activate what I believe is Mode 5 or the "ring mode" (because the nodes are shaped like a ring), which coincidentally is not only the easiest place to hold the plate, but coincides with the frequencies we care most about for a mandolin's tonal range.

For a first instrument, you would not be too far off if you simply do the following:
- Hold the free top and back plates from 20% in from the rim frequently during carving. When it sounds really nice, sustained, and meaty, then stop carving. Compare the note to a piano if you like. It should end up ideally in tune with some note in the octave above middle C. Not too far above middle C, though, or your top is too stiff and will sound tight and lacking bass response.
The back should be higher than the top. Try for a fifth or third and see how that does. But try to keep it from being just some random relationship, or else your instrument will have some random overtones which can be really annoying. I have one of my early instruments which demonstrates this very well.. it never sounds really "in tune" because the harmonics are pretty off the wall terrible.
Then try to get the tone bars to just sound nice in relationship to each other... treble bar is a little stronger/stiffer than the bass bar, but the bass bar can have more mass (lower/fatter bass bar, taller/thinner treble bar).
That's where I'd start...

[StuartGold]

Wow! thank you for such detailed info. I very much appreciate it. It's a LOT to think about.

[Marty Jacobson]

Yeah, just don't over-think it. You'll learn more by diving in and seeing what happens than having a stack of parts sitting in your shop for three years while you try to get everything perfect. I know a lot of kit builds end up getting stagnated due to this kind of thing. Just build it and get a feel for it, and if you do a nice setup on it it will doubtless sound pretty darn good compared to anything you'd find at Guitar Center.

[sunburst]

I don't know how successful searching the topic of tap tuning would be here, but there have been quite a few discussions, and enough diligence might turn them up, especially if you're good at using the search feature here (Mike Edgerton is the master). Suffice it to say that there is no agreement on what tap tuning does, how to do it, whether is is worth doing, or even if it can be done.
My advise, on a first mandolin, is to ignore that part of the book completely. As for your guitar, you didn't "luck into a nice sounding instrument", you followed the tried and true and got good results, just as you can with a mandolin. If you want to start learning about tap tuning and make up your own mind about it's utility, feel free, but don't let it frustrate you and cause you a lot of anxiety (as that section of the book has for many who have used it as a guide). And feel free to abandon the process at any point where it seems to not be working, and don't worry what notes your parts produce if you can't get them to your goals. It will all be fine regardless.
Some experienced builders tap tune with good and predictable results, but they are working with a data base from their own past work (Peter Coombe has written some stuff about it, and his writings are probably the best information about a comprehensive approach to tap tuning). Others (including 'yours truly') don't tap tune. I abandoned the attempt of trying to make sense of all the different and apparently random results I was getting from it years ago. If consistency of sound is the goal, I can tell you that tap tuning is not necessary for consistency of sound. If varying the sound is the goal, I can't imagine building a personal database big enough to be useful for that. So, opinions vary on it's utility, but it is certainly possible to build good sounding mandolins without tap tuning.

[belbein]

This advice was passed on to me in a class on guitarmaking I took last week. It's not really tuning: what it is is maximizing vibrations throughout the "plate." All that stuff about different notes and frequencies: when I first got here I spent a lot of time reading physics stuff about sound, by people like Cohen and Cooke and others. Bottom line--Simonoff's stuff may not be bunkum, but it's beside the point. What you're doing is carving the back/front/tone bars (or braces, on a guitar) until the point where you hit the maximum vibration. If you listen to it--hold it in a node (a dead spot) and tap with your knuckle--the "plate" will have some sustain, almost reverberation. That's what you want. You carve until you get that, then stop. If you NEVER get it, then you either figure the plate is a dud and start with another one, or you figure you haven't gone far enough. There's no scientific point where you've got the perfect top, other than what your ear tells you. If there was, everyone would be able to do it. You should take solace in the fact that machines and wages slaves in SE Asia make pretty damn good instruments--and so will you. I agree with Mr. Hamlett (always a good idea): ignore that stuff about notes and concentrate on the vibration you can feel. Do your best. You're bound to be pleasantly surprised. (And stop worrying, for god's sake. You're making ME nervous!)

[peter.coombe]

In a first instrument I would ignore all the tap tuning stuff and just build it. There are many more important things to worry about. However if you want to read my stuff here are the links -

http://petercoombe.com/jaamim7.html
http://petercoombe.com/jaamim8.html

[belbein]

Mr. Coombe, glad you chimed in. I can't say that I loved reading your papers, but I really appreciated the education. And all the work you put in testing the theories. I understood only a fraction but learned a lot.

One thing I disagree with you on is that beginners shouldn't worry about this. We worry anyway. Besides that, it's clear that this is like so many other things: you can't know how to do it until you have a lot of experience doing it. So we novices may as well start. The problem with all you guys who have been doing it a long time is that you have forgotten what it's like to START. The one thing that really helped me was this: you're carving to the topo map--but that's only a rule of thumb. Then then you're going just a little further. What you're looking for is that place where the plate reverberates. Then you stop. Then put on the tone bars and trim, and listen, and trim and listen. When you get to the place where you've carved one sliver beyond a sweet vibration, stop.

So, Stuart, as one beginner to another, I suggest you should go ahead and try to adjust the vibrations (not "tune"), take careful notes of what you're doing, and then just go ahead and build the thing. If it has beautiful tone, repeat. If not, adjust. But this is clearly art, not science, and it changes with every piece of wood, and every maker's approach to the wood and every maker's hand on the chisel. Everyone--Messrs. Coombe, Cohen, Simonoff, &c.--all agree that you can't do this "tap tuning" thing until you have a lot of experience doing it. And you can't get experience unless you do it. So by the nature of the thing, at the beginning you're flying blind. So start doing it ASAP and see what you get. Be assured: if you did nothing, your mandolin would sound cool. That your 100th will sound better is irrellevant at this point.

Forget all that crap about tuning to 420 mhz and tuning this part to D# and that to A flat. It's not that it's WRONG--I'm not smart enough to know that--but it's irrelevant to we beginners. Just feel the vibrations and listen. When you hear the reverb, you're as close as we beginners are going to get before #100.

[StuartGold]

I want to thank everyone who has chimed in on this topic. Your words are very appreciated. I wont]t probably be in the thick of it until a week or so but I'll try to remember and synthesize what everyone has said and find a starting point. Can't wait to give it a try. It should be quite a ride!

[johnn0hj]

Forget all that crap about tuning to 420 mhz ....

Wow, that's some ultra high frequency I think my 70cm ham rig reaches that.

[JeffD]

Forget all that crap about tuning to 420 mhz

Microwaves!

[Tukanu]

I realize this thread is 10 years old, but the subject is new to me. I have built more than 100 flattops and never worried too much about tap tone, other than noting what a soundboard sounds like when I am satisfied with its stiffness.
I have just started making carved tops, mostly with the guidance of Graham's book on mandolins.
He makes reference to a tap tone in the braced top of around a G4.
I don't intend to invest in a scope. My 'Snark guitar tuner' gives me a pretty consistent reading, and it is in the range of F to A.
So, my question is: Is this the same reading that a scope would produce?

The picture on the left shows a reading of F before carving the braces. The one on the right shows G# after carving the braces.

[j. condino]

Yeah, just don't over-think it. You'll learn more by diving in and seeing what happens than having a stack of parts sitting in your shop for three years while you try to get everything perfect. I know a lot of kit builds end up getting stagnated due to this kind of thing. Just build it and get a feel for it, and if you do a nice setup on it it will doubtless sound pretty darn good compared to anything you'd find at Guitar Center.

+1000!