sceyral
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Post by sceyral on Oct 25, 2021 8:51:01 GMT
As a Physics teacher (and amateur musician, and Reso guitars lover), I was involved, many yrs ago, in a French national contest : "The Physics Olympiads", where grade 12 students work on a mini research project. We chosed : "Frequency Spectrum of a RESOPHONIC GUITAR" Without any knowledge in lutherie or acoustics, these pupils built a resophonic Lap Steel, and studied its spectrum : because of the simplicity of the instrument, it was easy to switch, from the cone to a plain wood discus (with a bridge) making comparisons easy : we discovered that the main contribution of the cone was a strong reinforcement of some special frequencies : the [1000 Hz-3000Hz] domain, the exact zone of prominent human voice harmonics! * the student group was very proud to be awarded with a Bronze Medal, at the Olympiads Finals! I don't know if many forum members can read french, but you'll find the report for that work in the attached file below. As a retired person today, with a vast amount of free time, I could translate it (on request by interested members), if i'm not too lazy... LE CONE RESONANT DES GUITARES NATIONAL.doc (320 KB)  |
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Post by pete1951 on Oct 25, 2021 14:09:40 GMT
This looks like a great project, why didn’t you teach at my school?
I would even have learnt French!
Pete
I notice you used a single 250k pot for the ‘blend’ control. How well did it work? I don’t think I have seen this style of control on a guitar before ( usually a dual- gang pot with a centre notch is used)
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sceyral
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Post by sceyral on Oct 25, 2021 15:04:17 GMT
This looks like a great project, why didn’t you teach at my school? I would even have learnt French! Pete I notice you used a single 250k pot for the ‘blend’ control. How well did it work? I don’t think I have seen this style of control on a guitar before ( usually a dual- gang pot with a centre notch is used) You'll find the wiring diagram on the report (with the preamp layout) if you can download it. In fact, our main goal was to remain simple, as high school students are not that capable in electronics! a) Not knowing where to record the sound, we needed two sources : one next to the neck and one next to the biscuit. b) The project had to be somewhat glamorous and the lap steel playable : it HAD to look like a real guitar ! c) To divide the project and give some work to anyone, I had to include a printed circuit board (preamp) and a primitive mixer. d) a simple switch, between the 2 PUps, could have been enough for our experiments. e) I HAD a 250k pot in my lab, my budget was not imperial, and it DID work ! (French Education ministry, Physics Olympiads Committee, and industrial sponsors allowed me a pharaonic 2k€ (12000 FF in those days) subvention for the whole project!) f) I had already used such a pot, on a personal and earlier project (copy of National Resolectric), with proven results. g) the main concern was to adjust the preamp gain, so that the piezo output level matches the magnetic mic. Best regards,  Attachments:
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Post by leeophonic on Oct 26, 2021 5:12:31 GMT
Judging by the amount of resophonic guitars I have owned there is something in the frequency of these things.....
Lee
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Post by pete1951 on Oct 26, 2021 7:29:00 GMT
Has the question ‘Why do resos sound so good?’ been answered? Probably not.
Have a group of school children been exposed to Resonator Guitars, and sound make? Definitely!
Could one of them may get to Paris and become an apprentice to Mike Lewis ? That would be something special.
Exposing young people to resos will also get them listening to blues and Dobro music, most of us on the forum are not ‘young ‘. (ok, I don’t have the statistics, I am making an assumption) so this project ( I can see several changes I would have made , but it may well have gone over budget and taken too long) was a brave attempt to spread the word. Well done Serge.
Pete
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sceyral
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Post by sceyral on Oct 26, 2021 7:54:57 GMT
to Pete1951 : none of them former students are luthiers, today : two (girls) are MD, and two (boys) are engineers. That contest was a significant promotion for the School and the City: the Mayor was so happy, that he welcomed the group to the City hall, and gave (to each of them) a nice MontBlanc fountain pen ! After the contest and the bronze medal, I arranged a "blues week" in my High School, with an exhibition, lectures on Blues History, and a wonderful concert : Patrick Verbeke (Vcl, Gt) and Claude Langlois (Dobro, National and pedal steel) came to our small town, played in front of hundreds of students : Claude played the students' Lap Steel on stage, making them proud beyond any limit. Olympiads students went to restaurant with the musicians... An unforgettable moment. I recently had news from a crew member (a girl, 43 yrs old, now working as cancer specialist Doctor, in an hospital) : she remembers that week, as a prominent milestone in her life...and still uses her MontBlanc pen.
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Post by Stevie on Oct 26, 2021 8:38:12 GMT
Some folks can measure their mark by comparing what's changed after dipping their hands into a bucket of water. Then you get a few who really do make a splash. And then fewer still for whom altruism is a mantra. You seem to be one of the relative few Serge.
e&oe ...
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Post by blueshome on Oct 26, 2021 9:43:04 GMT
I wonder if a similar exercise has been done with National style guitars - triplate and single cone? I’m sure the results would be different.
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sceyral
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Post by sceyral on Oct 26, 2021 11:07:04 GMT
I wonder if a similar exercise has been done with National style guitars - triplate and single cone? I’m sure the results would be different. Never read anything about that; it would be, anyway, pretty tough to do, the main concern being, in Physics, to study one parameter after another : "all things equal otherwise". Few brands can be used: Mule Resophonics (as I know) is the only one possible, as the same model (same body, same size, same alloy, same neck...) can house a biscuit type single cone, or a T-bridge tricone system... For other makes, the differences forbid any sensible comparisons (long or short body; steel, brass, or german silver; 12 or 14 frets; stamped or rolled F-holes; maple or mahogany neck; rosewood or ebony fratboard...) : it's endless. When Mike Lewis was building my Style 1 Triplate, I talked extensively with him, in his workshop : he made every mod "à la feuille" (by trial and error, and by ear) Open an online subscription, buy the guitars at Mules's, ship them to my home, I'll do the job, "Ad majorem Resophonic Science Gloriam"!.. |
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Post by linkous on Oct 27, 2021 6:49:45 GMT
Without any knowledge in lutherie or acoustics, these pupils built a resophonic Lap Steel, and studied its spectrum : because of the simplicity of the instrument, it was easy to switch, from the cone to a plain wood discus (with a bridge) making comparisons easy : we discovered that the main contribution of the cone was a strong reinforcement of some special frequencies : the [1000 Hz-3000Hz] domain, the exact zone of prominent human voice harmonics! Without much science about frequencies: Isn't the fundamental voice frequency (very) much lower? Something between 80 Hz and 300 Hz? |
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sceyral
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Post by sceyral on Oct 27, 2021 7:19:13 GMT
You're absolutely right, but no contradiction : when you sing a C4 note (262 Hz), you produce many, many frequencies at the same time (and NOT the only first one, as a human voice is not a sine wave generator!) : 262,524,1048,2096,4192... though the fundamental voice frequency domain is [80;300], the harmonics go far beyond : (500: 5000 Hz).
The energy for harmonics is much lower than the fundamental one, but we hear them (if not, we couldn't make any difference between two persons singin' the same note!).
Moreover, the maximum sensibility for our ears is around [1000;1500Hz] :any reinforcement for frequencies (in that domain), which is exactly what the resonator makes, is over detected.
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Post by Pickers Ditch on Oct 27, 2021 8:36:50 GMT
All of this thread is interesting reading and I, like Pete, wish that my Physics lessons included subjects, experiments and fun like this. So, Serge and his students have applied science to understand the physics and properties of resonator guitars in a strictly controlled experimental environment - a great achievement. The final part of sounding good comes from the artistic side though. Two seperate players can play the same guitar with the same set up - nothing changed - in the same room - within seconds of each other and the guitar will sound different to whomsoever is listening. It's all down to touch and feeling which cannot be measured scientifically. This is the magic of music - no two people/players sound the same playing the same guitar, fortunately. Serge, I applaud what you did with your students but having come up the scientific route through my long lifetime, I still prefer the artistic side of the equation as to what sounds good. Sorry to appear to be a sous-marinier  Bien a vous, PD |
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sceyral
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Post by sceyral on Oct 27, 2021 9:30:11 GMT
To Pickers Ditch : in fact, I'm two faced: both a Physics teacher (and a teacher's teacher) AND a guitar picker and blues lover (since my teenage) : Reso guitars have always been a deep mystery, since I discovered them ("Bukka" White and Fred McDowell, in 68, as I still was a HS student!). When that Physics Olympiads contest started, back in '92 (to bring more students to Physics ans Chemistry), I HAD to be a part of it! Working part time in a small town HS, we were far away from Universities and major companies (for sponsoring) : our subject had to be cheap, and reachable for students! The choice was obvious...
My students (though nice and motivated), didn't belong to the over educated upper class, so music was quite attractive: the Olympics winner that year (our main competitor, from a major technical HS in Lyon), made a radar system for airplane models : during the presentation, they could control the flight inside the University amphitheater : all the crew's parents were Engineers, PhD...
Today, I'm retired (70 yrs old), don't work much on Physics, but still play, daily, my Style O and Tricone !
And I do agree that the human side of guitar playing has nothing to do with Physics!..
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Post by blueshome on Oct 27, 2021 11:13:01 GMT
The last place I would start such experiments would be with a Mule. They do not have the typical National sound - I would start with a Style O and a Triplate.
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sceyral
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Post by sceyral on Oct 27, 2021 11:59:29 GMT
to blueshome : never seen (or played) a Mule gt before. Already played Amistar (good), Republic (fairly good), Johnson (awful) '80 era Dobro33 (hardly decent, quite good with a cone change), Fine Resophonics (wonderful) and National Resophonics(wonderful)... Explained above the reasons of that Mule choice.
A National Style o and National Triplate, head to head, comparison would be completely biased : to many elements differ. You will never know what you're measuring: cone? body size? alloy? neck length? Apertures size and shape? Thickness and nature of plating ? This is navigation by dead reckoning ("au pifomètre" ou "au doigt mouillé" !)
Even a 1930 and 1936 Style O rarely sound the same...: if John Dopyera (who experimented much) used 3 cones and a german silver body, he had good reasons (whatever the cost),causing the argument with Georges Beauchamp (single cone and brass body). I'm not sayin G.B. was stupid; Dopera was an esthete, and GB was a business man: as the National Co profits did stagnate, he considered that Tricones were not the answer...
Even the tiniest mod changes your sound: switching from maple to ebony (for the biscuit, on a StyleO or Duolian) is not negligible...
In fact, the general sound quality is not that important : what we study, is the contribution of EACH (isolated) factor, taken for granted we CAN isolate it.... It's a vast amount of work (maybe enough for a PhD...)
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