#1
|
|||
|
|||
What Are we Tapping For?
I've read where different builders of both acoustics & electric guitars are tapping the wood for tone. I certainly tap the wood to listen for the thud one gets when there's a crack in the wood, much like a baseball player would do when he hits the knob end of the bat on home plate to tell if the bat has a crack in it; but other than tapping the wood for crack detection and the resonance of the wood are you builders tapping to achieve a certain note or frequency for each piece, back, top, sides, neck, fingerboard and if so are you trying to tune the various parts of the guitar to a certain note(s), a certain amount of bass, mid-range or treble? If so are you trying to have certain parts of the guitar have more prominent frequencies, like the neck to be bright, but the body to be have more bass?
Thanks & Merry Christmas to you all! |
#2
|
|||
|
|||
Merry Christmas Mr Bond, while I can't speak for we I can for me. I tap firstly to gauge damping, a thud is high damping and a long gong is low damping. Then I tap via a mic into a spectrum analyser but I don't think that helps your purpose much, however its main intention is to tune the tops main mode of vibration (monopole) to a specific frequency.
Jim |
#3
|
|||
|
|||
Listening for the basic ring, attack, body, and sustain. Listening for pitch (not all people care about pitch, but classical guitars usually end up near G# on the top). Listening for over-tones.
__________________
---- Ned Milburn NSDCC Master Artisan Dartmouth, Nova Scotia |
#4
|
|||
|
|||
Hey Guys,
Thanks for the info.! Interesting to note one is trying to tap for a certain frequency or note like G#! Is this a similar reason why a person would not want a pickup over a harmonic like the imaginary 24th fret area, because one doesn't get the full spectrum of harmonics and overtones on a 22 fret guitar where the neck pickup is placed under the 24th fret as opposed to a 24 fret guitar and the pickup is more under the 26th fret? IE. It's better to have it tuned to a frequency or note less likely to disrupt keys or open tunings most people play in like E. Quote:
|
#5
|
|||
|
|||
Quote:
The 24th fret occurs, theoretically, at exactly 1/4 of the open string, low enough on the harmonic/overtone sequence that notes of that pitch can be heard, though I'm not sure of relevance that has to pickup placement. The 26th fret occurs at a MUCH higher harmonic/overtone, one that probably contributes little to the overall tone, and is thus likely irrelevant to pickup placement. Quote:
|
#6
|
|||
|
|||
The 24th fret is at 1/4 of the open string length; a 'node' (stationary point) for the 4th, 8th, 12th, and so on modes, and an 'antinode' (maximum excursion) for the 2nd, 6th, and so on, modes. A pickup with zero aperture (reading the motion of only a point on the string)would not 'hear' notes with a node at that point, and would pick up a lot of the antinodes.
As soon as you fret the string, the whole picture changes. Dana Bourgeois taps for the 'feel' in different spots. When I was able to track his process once at a luthier's convention, it seemed that he was tuning the pitches of different modes of vibration of the top so that they would couple strongly with other resonances, either of the air inside or the back. Strong coupling can be sensed as a 'kick' if you leave your finger resting on the top after you tap it. Many makers like to hear a wide variety of tones as they tap in different places. Some try for tones in a scale or ones that are harmonically related. Some advocate having all the tap tones fall between played notes, to avoid 'wolf' tones. |
#7
|
|||
|
|||
Quote:
|
#8
|
|||
|
|||
The thing I have never quite understood about tapping, is how the information derived aurally, from tapping, guides the builder's decisions about how to alter/rectify/fine tune the soundboard based on the received info.
It is a well documented fact that an experienced builder will be able to tell just by tapping that a certain amount of wood will have to be removed from such and such a brace in order to achieve the optimum tone once the soundboard is glued up and the box closed, but just how they arrive at their conclusions has always been a bit of a closed book to me ... When it comes to fretting and setting up a guitar to get maximum playability, I follow a set procedure which guarantees the outcome every time. I don't guess. I don't speculate. When it comes to constructing a soundboard, is there a similar set of rules which guarantees the best possible outcome every time, or ...is it just a crapshoot ? |
#9
|
|||
|
|||
Quote:
Start by understanding that string instruments, including guitars, historically were developed and improved by trial and error, er, I mean "empirical methods". The scientific theory regarding much of the acoustics and even mechanical structure of things largely came afterwards. And, most instrument makers, historically, likely weren't at the pinnacle of the scientific fields involved. Historically, the process of learning the craft involved apprenticing with someone already considered a "master", that is someone already well-established and knowledgeable in the field. Ideally, the master taught the apprentice "all" that he knew, bringing the apprentice fairly quickly ( a few years) to the current state of the art. A talented apprentice would build upon what he was taught, with each generation of apprentices gradually discovering new things about the craft that improve the instrument. This includes methods of work and methods of getting instruments to sound a certain way. These methods, historically, involved "feel" and "intuition". For example, Jose Romanillios once showed me a method he uses for determining appropriate stiffness of a top in a finished classical guitar. It involves squeezing the ends of the bridge with one's thumbs to determine how "springy" feeling it is and to watch how the top deforms as you do it. (He can also use this method to determine the thickness of the top, the placement of the braces and the height and width of the braces anywhere on the top, to within .1 mm.) The downside to the "feel" methods is that they need to be experienced first-hand. That requires either someone to teach them to you - "See, when you do this, that happens, feel how that feels when you do that..." or, "Do you hear THAT?..." - or a lot of experience in which one makes certain correlations via one's own observations. This can't be taught well in books, videos or on-line forums. In more recent years, considerable scientific measurement has been done on guitars and considerable science has been applied to guitar design and response - an amount unprecedented in the history of guitar making. These methods provide additional tools to achieve repeatable, specific desired results. These, potentially, take much of the "guess-work" out of doing so. They also are something that can, like the scientific method, bring an orderly, repeatable approach to guitar making. It begins to get closer to a formula in which some of the variables are known, measured and manipulated to produce a repeatable result. Potentially, it reduces some of/much of the "touchy-feely" part that was previously done by hands-on feel - something that took time, experience and, perhaps, a good teacher. While the scientific approach is quickly gaining momentum, it is, I believe, still largely in its infancy. To date, to the best of my knowledge, the most complete material on the application of practical scientific methods is found in Trevor Gore's books. I'm continuing to work through the material he presents - not an easy read and probably largely inaccessible to those without some science background. Obviously, many makers use varying amounts of both approaches - feel/intuition and science. Perhaps something to keep in mind is that there are now exponentially more "guitar makers" than ever before. Many now learn the craft via books, videos and the internet. Relatively few learn the craft in a traditional apprenticeship at a master's bench. This leaves the novice maker in a situation in which they don't learn the "feel" of the craft but the science may be well beyond their ability to apply meaningfully. For those in that situation, the craft becomes largely a woodworking project. That said, it isn't really that difficult to use a time-tested design to produce a steel string guitar with a very pleasant tone, one equal to many of the better factory-made instruments. |
#10
|
|||
|
|||
Quote:
Jim |
#11
|
|||
|
|||
Thanks for everyone's information! This thread was better than I thought it might be with lots of great info.!
|