Tap Tuning

[Shane Heinrich]

Hello everyone.I am rather new to lutherie and was hoping I could get some help.I have built two acoustic and five solid body electrics.I'm currently trying to learn more about tap tuning.I have read The Art Of Tap Tuning and it's been helpful.Where can I find information about the tunings of different guitar body types?

[Charlie Schultz]

Hi Shane and welcome! Note that we're primarily just testing the new forum software now, so your post might get better answered on our active site (http://www.mimf.com/cgi-bin/WebX). But someone may come along with some tips- I know there are many opinions of tap tuning.

[Dick (DT) Trottier]

Hi Shane,

I spent time looking for the same thing, some magic recipe, about five years ago with no luck. For me, tap tuning turned into an iterative thing, at first building to dimension and noting the pitch of different braces, then, on subsequent instruments, tweaking those pitches to intervals, full tones or semi-tones. Experiments were interesting, and the results were typically trade offs. For example, loosening the upper finger braces (lowering the pitch) gave a super warm tone but projection went way down.

In retrospect, I'm glad that there was no tap tuning recipe out there.... it keeps things interesting.

Good luck in your quest...

[Simon Magennis]

Where can I find information about the tunings of different guitar body types?

Kind of reminds me a bit about a joke concerning the lawns in Trinity College Dublin (which in fact were nothing very special).
Tourist: "How do you get the lawns to look so green?".
Guide: " Easy. Just water daily and mow once a week for 350 years".

So the answer to your question is carefully build a few 100 instruments and learn by experience.

[Craig Bumgarner]

I too have had little luck with tap tuning even though I am a tappin' fool and tap everything constantly during construction. Having built less than "100 guitars" though, I too have had a hard time drawing firm conclusions.

I read Mr. Smirnoff's book but have not tried his method of tuning parts to notes. That just seems off base in many ways, to me at least. What I did take away from his book however was the idea of deflection testing and THAT has been helpful. The way I use is to apply a weight roughly equal to the downward force of the strings on the bridge (20 lbs in the case of the Selmer style I build with an unglued bridge and tailpiece like an archtop) and measure the deflection. Over the last year, I've tested not only my own guitars during construction and upon completion, but also any other guitar I can get my hands on and permission to test.

Most recently, I finished a replica of a Castellucia D hole Selmer style guitar (acoustic, steel string) from the 1950s which I have the good fortune to play beside a couple nights a week. The original is a terrific sounding instrument with a very unique sound. Very loud and can cut through anything acoustically, very important in a 4-5 piece acoustic swing jazz group. Getting the physical characteristics are fairly easy but capturing the tone is, of course, much more subjective. I dimensioned the top and braces (as well as everything else) exactly like the original, BUT when I deflection tested it after gluing it to the rims, it had a good 40% less deflection, that is stiffer, than the Castellucia top. This clearly would not do so I thinned the braces (I had not yet installed the back) and the top until my deflection matched the original (.038" under a 20 lb load). Once completed, it sounds very, very close to the original. The combination of copying the physical characteristics AND the deflection testing where in my opinion a large part of the success.

Deflection testing measures the whole assembled top (or back) and a certain amount of common sense needs to be applied. There are lots of ways of getting the same deflection number. Imagine sides that were highly flexible and a 1/4" plate steel top for instance. You could still get .040" deflection out of that, but clearly would not have the same sound (if any). So deflection testing is not the complete story, but it does help me fine tune. If a top is the sum of its parts then testing the sum in some way should be helpful in understanding how the top will respond to input.

Some day, I'd really like to get my head wrapped around Alan Carruth's plate tuning with generated tones and node patterns.

Then of course there is Ervin Somogyi's tap tuning class ($5K + expenses, whew....).

Here is a picture of my little test rig, be it so humble. The plywood rim around the edge of the top is used on an unglued top to clamp it to the rims during testing in lieu of gluing. I have a couple different leg support options for the plank that supports the dial indicators which allows me to check sides and plates in the mold or completed instruments supported firmly. BTW, if you use this gig idea, be VERY careful with the weights. A ten pound weight dropped from 1 foot on a guitar top will pretty much ruin your day. Also, be sure to clamp down well as the weights destabilize the jig when applied.

[John Hall]

I stopped tapping and use the deflection test. I feel that it shows a better result to the actual strength and stiffness of the top. I feel that you can tap but you won't get real results as once the top is glued to the sides you change the frequency of the top. I get real numbers this way and I feel it helped to get my results more repeatable.

[Jeff Highland]

I can only suggest that you consign Siminoff's books to the garbage bin. The physics and other concepts are just too flawed and will lead you astray.
Trevor Gore's books on modal tuning are really the first worthwhile tap tuning method IMHO

[Jason Rodgers]

I read Mr. Smirnoff's book but have not tried his method

I suggest tonic and lime.

Craig, do you just test deflection at the bridge, or elsewhere on the top? David Hurd's "Left Brain Lutherie" method is about testing deflection all over the lower bout in a grid-like fashion. It would be interesting to know if you could get a little closer to that exemplary grand bouche by checking out the deflections in just a few other locations around the bridge (maybe 12 o'clock, 2, 4, 6, 8, and 10; or 2" in front and back of the bridge, plus under the bass and treble feet, etc.) without doing the super-thorough mapping that Hurd does.

[Ron Belanger]

I have found the method used by Kent Everett to work well for me. I have been using it for the last 6 instruments or so and I have found a big improvement in my results. More volume and sustain and balance. I still have a long way to go, but I think I'm moving in the right direction.

[Alan Carruth]

Dave Hurd tested one of my guitars that had been 'free plate tuned', and got just the sort of deflections he looks for. I think that we're all trying for the same things, and that any method that works is getting them, no matter how we approach it.

Alan Carruth

[Jason Rodgers]

That's really cool, and encouraging, to hear, Alan. Last time I remember one of these threads, you had mentioned that you and Hurd hadn't really been able to get together and swap info/ideas. Sounds like a lot of folks are having success with these methods, either separately or in combination.

[Andrew Porter]

Craig, when you tested the deflection on the original Castellucia, did you remove/loosen the strings?

[Craig Bumgarner]

Sorry to be slow coming back on this, I've been traveling without a computer.

Jason: I just test the bridge area, but surely testing elsewhere would be interesting. I've not seen David Hurd's book, so can't comment on his approach beyond saying it sounds like a good idea. It also sounds complicated, especially in the the adjustment of a new top. I should think every adjustment to a specific area would have implications elsewhere, so a full round of tests would be needed with each adjustment. For my purposes, I think I'm okay with testing just the bridge area for now. I could see adding a few areas and might do so at some point, but to date have. I might think differently on a guitar with a fixed bridge / string terminus like a classical or standard flattop.

Andrew: I test without the strings tensioned and the bridge removed. In the guitars I work on, the bridge is not glued down. When I apply weight to the top in the bridge area, what I'm trying to duplicate is the downward pressure of the strings on the bridge. In the guitars I work with, this works out to about 20-25 pounds. So, without strings and bridge, I apply 20 pounds in the bridge area and measure the deflection. I then strive to duplicate this when I build a new one. I find it is not difficult to build to a deflection of +/- .001".

I am very encouraged by Alan Carruth's comments earlier in this thread.

CB

[Barry Daniels]

I took the Somogyi class and have been attempting to put his techniques into practice. I think the key to his method is the use of a tapping form similar to what Craig shows above, but using screws around the perimeter instead of the weight to secure the top. I abandoned the form for several guitars since I use a domed top. The forms Ervin used in his classes require a flat top. So I am working on a tapping form that will use radiused components to allow the radiused top (and back) to be clamped into place. Initially, the top will be clamped upside down to allow access to the braces. Once carved, the top will be flipped over and then the back will be clamped on upside down for tapping and carving trying to make it work with the top. I will keep you posted on my progress.

[Douglas Ingram]

I've been tapping my tops and backs as I build, not to work to any particular end point, but rather to follow the changes that occur as I work.

I have been finding deflection a very useful aspect in recent builds ( I build mostly classical guitars) since I saw Daryl Perry examine one of my guitars and one of the first things that he did was to hold the lower bout of the guitar and press down on each bridge wing with his thumbs feeling the deflection resistance. I still need to press down on a lot more guitars in order to get the feel of what I should be working towards.

[Craig Bumgarner]

I've been tapping my tops and backs as I build, not to work to any particular end point, but rather to follow the changes that occur as I work.

I have been finding deflection a very useful aspect in recent builds ( I build mostly classical guitars) since I saw Daryl Perry examine one of my guitars and one of the first things that he did was to hold the lower bout of the guitar and press down on each bridge wing with his thumbs feeling the deflection resistance. I still need to press down on a lot more guitars in order to get the feel of what I should be working towards.

I've others do this too. I do the same, but my taps and thumb pressures are not yet "calibrated". Over time I might be able to judge with just my thumbs, eyes and ears, but for now, the deflection jig is a big help.

CB

[Bill Hicklin]

I've tried MIMF's own Alan Carruth's method of using Chladni patterns twice now and found it made a huge improvement over my previous steel-string guitars. Here's his article: [look for Alan's web page]. More comprehensive how-to article in the GAL Big Red Book.

[Craig Bumgarner]

I've tried MIMF's own Alan Carruth's method of using Chladni patterns twice now and found it made a huge improvement over my previous steel-string guitars.

The first impediment I've had to trying Alan Carruth's method has been the equipment required. What do you use?

[Darryl Young]

I recommend Al Carruth's video and Trevor Gore's books (Design and Build). Another video I learned some practical things from is John Mayes video.

[Bill Hicklin]

"The first impediment I've had to trying Alan Carruth's method has been the equipment required. What do you use?"

1) a PC running SweepGen (free downloadable test-tone app)
2) my old stereo amp
3) an old hifi speaker, flat on its back, with little foam blocks to support the plate
4) a can of loose tea leaves (makes for good jokes later)

2 and 3 can be replaced by a guitar amp. 4 can be just about any lightweight granular stuff.