Thank you Alan Carruth!

Construction and repair of Classical Guitar and related instruments
Paul Micheletti
Amateur luthier
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Location: San Diego, CA

Thank you Alan Carruth!

Post by Paul Micheletti » Mon Apr 23, 2018 6:25 pm

I was working hard and fast to get a guitar done before a show this last weekend. I got the strings on this guitar on Thursday for a show on Saturday. Just in time!

I was tuning it up to pitch, and heard some truly awful sounds come out of this beautiful guitar on the open A string. It created a resonant zithery wowowowowowowow noise that sounded absolutely dreadful. Humming into the soundhole showed that the main body resonance was directly on the open A pitch. Dismay set in. This is the first guitar I've made with a sound port, and the added aspiration from this port moved the resonance up right onto an open string.

I remembered this recent thread regarding a resonance on G and reviewed all of Al's suggestions there:
viewtopic.php?f=11&t=119000#p1266337

I just completed finishing on the guitar, so modifying the shape of the ports was undesired because I would have to refinish with only another couple of days until the show. So I scrolled down to the suggestion of loosening up the back braces. My back has 4 braces. The upper ones are about 1/2" tall in the center and the lower ones are pretty tall at 5/8", so there is no structural risk in removing material from them. I created a stack of about a dozen layers of blue masking tape 4" long and stuck this thick stack of tape to the third brace down (one of the 5/8" tall ones) and it moved the pitch down to just below the resonant A. From Alan... added mass is equivalent to lower stiffness so I know what brace to shave down.

I loosened the strings and took out my tiny brace plane and lowered that back brace down a bit. I have huge hands, but I was still able to plane this brace down a bit under control. Tightened the A string back up to pitch, and the resonance was reduced. Then lowered the pitch of the string a bit until I heard the awful warble. The warble was still a bit closer to the A than the G# pitch, so I planed a bit more off that brace until the resonant pitch was exactly halfway between the G# and A.

The guitar hasn't sold yet, but a couple of folks I met at this show are very interested. Thank you Alan for providing the great info to quickly salvage this instrument at the last minute!

I'll post up some pictures of the guitar to this thread soon...

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riemsesy
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Location: Netherlands

Re: Thank you Alan Carruth!

Post by riemsesy » Mon Apr 23, 2018 6:32 pm

you know this is a heart warming post of you.
to read such a gratitude gives me a smile on my face :)
Best regards, Richard Frank
-Yamaha GC22s
-Raimundo 128c

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souldier
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Re: Thank you Alan Carruth!

Post by souldier » Mon Apr 23, 2018 7:26 pm

Plugging the sound port usually drops the pitch around a semitone as well, depending how large it is. Some also add a mini tornavoz to also bring down the pitch to counteract the raising of the pitch caused by the sound port. Quite amazing how many factors come into play in producing sound from an acoustic instrument. Glad things worked out for you.
"Success grants its rewards to a few, but is the dream of the multitudes.
Excellence is available to all, but is accepted only by a few." - Christopher Parkening

Paul Micheletti
Amateur luthier
Posts: 553
Joined: Sat Jan 16, 2010 12:48 am
Location: San Diego, CA

Re: Thank you Alan Carruth!

Post by Paul Micheletti » Mon Apr 23, 2018 7:33 pm

Hi Souldier, I tried plugging the soundport with my hand, and it didn't seem to do much. Not nearly as much as loosening up the stiffness of that back brace. I thought about adding a mini tornavoz, but the time crunch made that less desirable. Deadlines are quite motivating!

Paul Micheletti
Amateur luthier
Posts: 553
Joined: Sat Jan 16, 2010 12:48 am
Location: San Diego, CA

Re: Thank you Alan Carruth!

Post by Paul Micheletti » Mon Apr 23, 2018 10:44 pm

Here's a few pictures of this guitar that Alan helped provide insight into resolving an unwelcome resonance. It sounds clean and clear now.

My 9th classical:
Image

This is the Port Orford Cedar neck that was so difficult to carve in a thread here from last month:
Image

Nice set of Indian Rosewood, with curly maple bindings:
Image

Image

My Ram horn rosette design. White faces looking into the soundhole, brown faces looking away:
Image

Headstock and fingerboard are both Indian Rosewood too. With Gotoh premium tuners.
Image

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bacsidoan
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Location: Ohio, US

Re: Thank you Alan Carruth!

Post by bacsidoan » Mon Apr 23, 2018 10:53 pm

Beautiful guitar! I like the rosette and the fingerboard a lot. I had a guitar with rosewood fingerboard, and it did wear out on me (scalloping) after I played it daily for a few years.

CT20
Posts: 134
Joined: Mon Aug 19, 2013 11:19 pm
Location: Connecticut

Re: Thank you Alan Carruth!

Post by CT20 » Mon Apr 23, 2018 10:58 pm

Looks great! So happy for you that you solved the sound issue by remembering the reference from such a great source of knowledge.

Di Mauro
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Joined: Tue Apr 10, 2018 11:15 pm

Re: Thank you Alan Carruth!

Post by Di Mauro » Tue Apr 24, 2018 12:29 am

That is a really nice classical guitar you made. The port orford cedar neck stands out. I’m carving a IRW neck right now, what a pain In the butt. There are a lot of inspiring reads and pictures etc for nylon sting guitars on this site. Thanks for showing us your 9th classical build

Stephen Faulk
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Re: Thank you Alan Carruth!

Post by Stephen Faulk » Tue Apr 24, 2018 5:37 am

Nice work.

I like the Port Orford neck, I guess you got the rasps out. I have a wall lined with neck sized pieces of Hinoki been eyeing them for necks someday. The only thing that holds me back is really the majority of players are slow to uptake new materials. You can pour your heart and soul and best work into a material they are not accustomed to.......

Did you put any carbon fiber spars in the neck?
Patience at the bending iron pays in rounded dividends!

Alan Carruth
Luthier
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Re: Thank you Alan Carruth!

Post by Alan Carruth » Tue Apr 24, 2018 2:11 pm

It's nice when something works; it can seem like a bit of a welcome change sometimes! As souldier says, the guitar is such a complex thing that there are usually several approaches that will help. Having a few choices is wonderful, especially when a deadline looms. It's a nice looking instrument. Those ram's horns have me thinking....

Paul Micheletti
Amateur luthier
Posts: 553
Joined: Sat Jan 16, 2010 12:48 am
Location: San Diego, CA

Re: Thank you Alan Carruth!

Post by Paul Micheletti » Tue Apr 24, 2018 4:53 pm

For bacisdoan: Fingerboards are always a tradeoff. Ebony does wear better over the years than rosewood, but it comes with lower stability. Ebony really likes to move compared to rosewood, so you get the pointy fret ends more often with humidity swings. This is a student-level instrument (and I don't expect all students to properly humidify their instruments) so I chose rosewood.

For Di Mauro: I cannot get my head around the idea of a solid rosewood neck. The thought of the neck weight alone makes me wonder how easy it would be to play. Is there a benefit for having a rosewood neck? Have you done one of those before? I wish you luck carving that!

For Stephen Faulk: I did dig out the rasps, but only to dig a trench to go across grain to get the target level for heel and hyoid transistions. I wrote up the method used here: viewtopic.php?f=11&t=118942#p1266182.

I didn't put any carbon fiber reinforcement, but did insert a large quartersawn hard maple reinforcement. The core of the neck is 3/4" wide by 1/2" deep of hard maple. I'm not sure that this neck needed it, because it was the stiffest neck blank I've ever seen. My "scientific method" for measuring neck stiffness is to put the blank on my bench, support one end up off the bench with a chunk of wood, wrap one finger under the blank, and then lean my body weight on the middle of the blank. If my finger gets squished, it's a floppy neck. If I can't feel it move at all, it's stiff. Most Mahogany and Spanish Cedar I can feel some flex, but not a lot. This POC neck had no flex at all. And it's about half the weight of Mahogany.

Everyone who has played it has remarked upon the lightness of the neck. Not only the color, but the weight. I keep forgetting to weigh the entire guitar, so I don't know that number. But it is very light.

For Alan: Thanks again!

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souldier
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Re: Thank you Alan Carruth!

Post by souldier » Tue Apr 24, 2018 5:48 pm

Paul Micheletti wrote:
Mon Apr 23, 2018 7:33 pm
Hi Souldier, I tried plugging the soundport with my hand, and it didn't seem to do much. Not nearly as much as loosening up the stiffness of that back brace. I thought about adding a mini tornavoz, but the time crunch made that less desirable. Deadlines are quite motivating!
Try stuffing it with a cloth and see what happens. I've tried this myself with several guitars and it usually equates to a semitone drop, unless the hole is very small to begin with. This is why I like guitars with adjustable magnetic covers because it allows the player to adjust the "volume" of the soundport as well as shift the resonances around based on what fits the song best.
"Success grants its rewards to a few, but is the dream of the multitudes.
Excellence is available to all, but is accepted only by a few." - Christopher Parkening

mlau
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Joined: Thu Jan 14, 2016 5:42 pm

Re: Thank you Alan Carruth!

Post by mlau » Mon May 14, 2018 3:16 am

Paul Micheletti wrote:
Tue Apr 24, 2018 4:53 pm
For bacisdoan: Fingerboards are always a tradeoff. Ebony does wear better over the years than rosewood, but it comes with lower stability. Ebony really likes to move compared to rosewood, so you get the pointy fret ends more often with humidity swings. This is a student-level instrument (and I don't expect all students to properly humidify their instruments) so I chose rosewood.

For Di Mauro: I cannot get my head around the idea of a solid rosewood neck. The thought of the neck weight alone makes me wonder how easy it would be to play. Is there a benefit for having a rosewood neck? Have you done one of those before? I wish you luck carving that!

For Stephen Faulk: I did dig out the rasps, but only to dig a trench to go across grain to get the target level for heel and hyoid transistions. I wrote up the method used here: viewtopic.php?f=11&t=118942#p1266182.

I didn't put any carbon fiber reinforcement, but did insert a large quartersawn hard maple reinforcement. The core of the neck is 3/4" wide by 1/2" deep of hard maple. I'm not sure that this neck needed it, because it was the stiffest neck blank I've ever seen. My "scientific method" for measuring neck stiffness is to put the blank on my bench, support one end up off the bench with a chunk of wood, wrap one finger under the blank, and then lean my body weight on the middle of the blank. If my finger gets squished, it's a floppy neck. If I can't feel it move at all, it's stiff. Most Mahogany and Spanish Cedar I can feel some flex, but not a lot. This POC neck had no flex at all. And it's about half the weight of Mahogany.

Everyone who has played it has remarked upon the lightness of the neck. Not only the color, but the weight. I keep forgetting to weigh the entire guitar, so I don't know that number. But it is very light.

For Alan: Thanks again!

Paul,

Thanks for the tip on the neck blanks.
I'm thinking of getting back into building, and have a stash of port orford cedar...

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