Ways or devices to let the back of the guitar resonate

[rio]

Wow, thanks to both of you. That is all incredibly interesting info.


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[Matt Cushman]

The key to building consistent performing guitars is in predicting how each part will perform in the finished guitar. That is one reason I always check and record a plates deflection at a set force. The deflection test has been around for awhile in mandolin building for the simple reason that it works. When judging a plates stiffness using thumb pressure and other methods you have to depend on how it feels while being flexed, which is hard to record on paper.

[brewster]

i have tonegards i use with my mandolins. it does what its supposed to and allows max back interaction for the volume and tone. very audible diff standing w/ and w/o the tonegard. gonna get one for 16" archie soon, but when i sit with the archie i tilt it just a bit to get the back off the belly land.
david grisman and rickie skaggs , among the top mando world stars, use them.

[brewster]

good trick matt! one of my violin maker friends uses a 2lb wt and measures 4 spots, before and after the F holes are cut. Red Diamond mandolin maker don macrostie also uses deflection ((has made a cool jig to give him 6 deflection point readings (3/side) at a time)) to get max sound production and consistency in his instruments. i have his first july 9th model and its fabulous.

[Ol' Fret]

The key to building consistent performing guitars is in predicting how each part will perform in the finished guitar. That is one reason I always check and record a plates deflection at a set force. The deflection test has been around for awhile in mandolin building for the simple reason that it works. When judging a plates stiffness using thumb pressure and other methods you have to depend on how it feels while being flexed, which is hard to record on paper.

Matt, plate deflection tests are great - I didn't intend to be dismissive in my post. Others use to define the Chladni patterns for getting well-tuned free plates, a loudspeaker below the anti-nodal area, audacity, etc. Whatever works for you is fine. OTOH, the old masters didn't have these aids, but trained their sensorium steadily - which led to some superb results.

There are good luthiers who claim that they don't tap tune, and I'll take them by their word. Anybody who is getting consistent results is doing something, but maybe not consciously. Therefore it's doubtful that really good carved archtop instruments can be mass-produced in a consistent and mainly profit-oriented way, like the shareholders demand today in the global market. That and the possible - though not compulsive - feed-back problems of the really resonant acoustic-electric archtop models was the reason why the bigger manufacturers soon turned to the laminated guitar construction: cheaper materials, smoother sounding and more consistent and predictable tone, less trained employees, and - at the bottom line - higher gains.

[Matt Cushman]

Matt, plate deflection tests are great - I didn't intend to be dismissive in my post. Others use to define the Chladni patterns for getting well-tuned free plates, a loudspeaker below the anti-nodal area, audacity, etc. Whatever works for you is fine. OTOH, the old masters didn't have these aids, but trained their sensorium steadily - which led to some superb results.

There are good luthiers who claim that they don't tap tune, and I'll take them by their word. Anybody who is getting consistent results is doing something, but maybe not consciously. Therefore it's doubtful that really good carved archtop instruments can be mass-produced in a consistent and mainly profit-oriented way, like the shareholders demand today in the global market. That and the possible - though not compulsive - feed-back problems of the really resonant acoustic-electric archtop models was the reason why the bigger manufacturers soon turned to the laminated guitar construction: cheaper materials, smoother sounding and more consistent and predictable tone, less trained employees, and - at the bottom line - higher gains.

I enjoyed your post Ol' Fret. I tap and flex the plates throughout the carving process but I always check the deflection before assembly. It is a simple but informative step. Just a very slight thinning of the recurve area can result in a measurable change in the flexing of a back plate. Flex testing was a big step forward for me. I should also mention I most often build with acoustic goals in mind. If feedback is a problem you may have to plug the F-holes.

[neatomic]

here's jimmy bruno retelling his freddie green story (around the 2:30 mark)

cheers

[Alter]

how about holding the guitar sideways (with the headstock pointing about 45 degrees towards the front)? The way say, adam rogers or rodney jones play? It gets some getting used to for your fretting hand, but it 's easier on the other hand, and there is much less friction and contact between guitar and body.

[Gato Jazz]

Considering that's the guitar's top vibration the one producing and projecting the sound, finding a way to allow the back to resonate, will in fact reduce in half the heard projection of the sound.

Why this might be good thing?

I'm all ears!

But damping it with something soft like your body will still suck energy out of the system, wouldn't it?. The vibrating back will transfer that energy to you body, which in turn will dissipate is, but not as audible sound. Unless you have a rock hard body (hit the gym!) I think damping the back of a guitar with your body will not increase the sound we get.

By the way, what's your connection with Argentina? I've been to Casa Núñez a couple of times myself (I live in Buenos Aires). Would that guitar-inside-a-guitar concept be similar to the "Virzi tone producer" inside the old Loar L-5? Or the wooden resonator inside the first Selmer-Maccaferri grand bouche guitars?

[Jp267]

A few post in and it's already a great thread. Lots of good stuff. Thanks all!

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[LtKojak]

what's your connection with Argentina?

Born and raised.

I've been to Casa Núñez a couple of times myself (I live in Buenos Aires).

Does Casa Núñez still exist? Wow! Talking about a blast from the past! I have a diploma of classical music performance from the Manuel de Falla Conservatory in Buenos aires.

Would that guitar-inside-a-guitar concept be similar to the "Virzi tone producer" inside the old Loar L-5? Or the wooden resonator inside the first Selmer-Maccaferri grand bouche guitars?

For what I remember it was, it doesn't seem to be either of those. His idea was a suspended smaller body inside the body, but I wouldn't know without looking at the patent. It's unfortunately not present in Google patents.