babyhead
Well-known member
I did a search for it here and didn't find much. Who has followed the link?
Genius. I want one.
JohnRoberts...
Genius. I want one.
JohnRoberts...
The spacing matters for very precision note tuning as the speakers and surface area of the tuner, if too close to to the drumhead, they acoustically couple and increase the effective mass of the drumhead shifting the note very slightly (lower). The spacing using the standard struts we provide deliver accuracy within the resolution of the tuner. While the basic technology works (I have a tympani in my lab) we do not currently support tuning tympani which have no raised rim support to rest on, and the drum resonances are very much different so the scan algorithm is completely different. The better behaved overtone relationships would be much easier to work with, while the lack of simple mechanical support is more difficult.I was wondering too. John knows some about drums, assumes his customers do too, and I'm left in the dust. Zig-zagging through the manual gave me enough clues.
It sits above but close to the skin. How you do that is not too important. Apparently he supplies some bridge-work to suit common drums, tympani may need adaptation, and if nothing else you steal some curtain rods and wood-scraps and duct-tape.
There are interactions between the two heads. At the lowest fundamental both heads act as one system. The 1st overtone which I use is not significantly affected by second head. I describe this in detail on my website see https://www.resotune.com/About_drums.htmIn that position, a speaker sings a sliding tone and the ear or mike hears the skin resonate at its preferred frequencies.
If you do that to a 1-string violin, you get several body resonances and several string resonances. You can tell which are string because they are narrow and very nearly exact multiples (440, 881, 1323...) while body resonances are broad and not so harmonic.
A drum's shell resonances are weak. There may be a second skin but when measured very close to the top (batter) skin the bottom skin is weak. The circular membrane's resonances are not even close to the 1,2,3,4 harmonic series of a string, but the ratios are well-known (for normal shapes, squares, circles; you build a lima-bean shape drum it will have different ratios).
PRR is close.. The two speakers couple into the same general node. My strategy of using two microphones is to locate one mic over the midpoint of the drumhead and the other spaced a few inches toward the rim. For the (0,1) mode fundamental both mics get a strong reading, for overtones of the (1,x) series there will be a null in center mic and strong signal spaced away from the midpoint. While great in theory this alone is unreliable if tuner is not precisely positioned or drum rattles and burps. Secondly while the math is well defined for a single drumhead, the coupling of a second drumhead more in one resonance mode than others causes an offset between the strict mathematical relationships between resonances. I use a combination of multiple strategies and the tuner can still be fooled by a too loose drum head that isn't vibrating simply or from very poor tuner placement.Now, John's patent and product shape show/suggest two speakers far enough apart to excite two areas. And he has animations showing how the second resonance wobbles half-and-half. So I'm thinking that this is how the micro-brain knows that it has found second resonance, except it would seem to find it as a null not a peak. Well, sometimes it is easier to dip a null than find the tip of a hill. And surely John spent much time with tinker-toy speaker/mike arrays and a 'scope before picking this particular technique. I'm glad he did it, and am glad it wasn't me.
Anyway, from the second resonance you can predict and check the first resonance. If the prediction fails, you could really have found the 5th resonance of a super-loose skin (drums are not as standardized as piano notes, and even that piano-tuner machine sometimes got lost).
yes.. cleared head has more good sounding sustain, less undesirable noiseThen it gets into skin set-up theory. Anybody licensed to possess a drum-key "should" know this stuff.... I don't.
Analogy: a marimba bar has two resonances. The lengthwise resonance is the pitch, different on each bar. You can also excite a sideways resonance, weaker, higher, and about the same on every bar (they's all the same width). The marimba player strikes to excite the length and not the width. Obviously a skin with the 12 and 6 (o'clock) pegs tight and the 3 and 9 pegs loose could have two resonances, and that would not get the whole skin working together.
Analogy: piano has 3 strings per higher note; this improves Sustain. Energy transfers from one string to another and the net result is longer energy storage. If the three strings are not very near the same pitch, it is not only dissonant (sour, honky-tonk), the sustain drops off fast. Presumably getting the whole skin working together has some similar benefit on a drum.
I am playing with DSP and have some ideas but haven't yet found an approach that works without the two speakers. They do not in fact couple into different nodes but acoustically couple to the same drumhead node. Their spacing is to straddle the lug and isolate it from the other lugs for measurement and adjustment. Doing this with only one speaker, or external excitement, can still be adjusted but does not readily converge. Not unlike when tuning by ear you must sometimes go around the lugs a few times because they interact with each other. I could make a much cheaper tuner but the lack of quick convergence is annoying to me and inappropriate for a precision process.So this machine seems to require you to move it to straddle each key, to get all 8 tuning pins and their skin-sectors singing the same frequency. We could picture a version with 8 speakers and no walk-around, but drums come different sizes and sometimes more/less pins. And the full-head tuner would be too big for the headphone/pistol case he offers to carry it, really a major addition to the drummer's burden. When the base 2-speaker model falls to $39 (gitar tuners have fallen lower, which was inconceivable when the first ones came out), John can re-goose the market with bigger one-step versions for drum-techs who value speed more than price or portability.
The tuning to a specific pitch is a fallout of the clearing process. As long as I have a crystal time base, and I predict someday it will be used, I provide that capability. My very first prototype was analog but it quickly became obvious that an analog approach required far too much customer involvement. Perhaps sophisticated drum techs could master such a system but I needed to reduce this to push a button and it finds the resonance, push another button and arrows tell you which way to turn the lug. I still have customers who can't master that, but drums are not simple instruments.Obviously if it can sense each section, it can sense the whole drum if you want a specific pitch. This is a matter of interpretation because a circular membrane does not have the simple 1,2,3,4 overtone progression of a string or pipe, and the "sense of musical pitch" is not so strong. Some drummers pitch, others just go where the head and shell sing together nicely and the drum-kit has a nice spread of pitches. The optimum overall-pitch algorithm may be different from the peg-balance algorithm; that's why he has a micro-CPU instead of ramp-generators and flip-flops. Another page of code, another menu-item, it could drum-hum "Dixie" if the market wanted that feature.
Movie on drummercafe site is not loading for me, even after you said "fixed", but it may be "me" or this computer. One of your neighbors must have a camcorder for grandchild movies, slip him a six of beer to shoot a clearing-round and post it on YouTube. You can add URLs in YouTube descriptions, but nothing beats printing BIG on a card for your closing shot.
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