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Anyone use Chladini testing for archtops?

PostPosted: Thu Nov 09, 2017 6:54 pm
by Eldon Howe
Anyone use Chladini testing for archtops?

I tried it on my last Nomex top archtop, but all the glitter just moved to the edges in most modes?

Re: Anyone use Chladini testing for archtops?

PostPosted: Thu Nov 09, 2017 8:28 pm
by Peter Wilcox
I'd think you need a flat level surface - otherwise the glitter just mostly goes down hill.

Re: Anyone use Chladini testing for archtops?

PostPosted: Fri Nov 10, 2017 6:29 am
by Beate Ritzert
Chladni figures in a raw archtop plate:

http://www.gitarrebassbau.de/viewtopic. ... 08#p107708

(and please excuse my link into that other forum - i don't know a better way to refer to these).

Re: Anyone use Chladini testing for archtops?

PostPosted: Fri Nov 10, 2017 11:05 am
by Eldon Howe
thanks Beate,
I could not find a translator. But this helps a lot.
Just to complicate things this is a 27" scale Baritone 8 string like the taylor.

Re: Anyone use Chladini testing for archtops?

PostPosted: Fri Nov 10, 2017 1:17 pm
by Alan Carruth
I've been using Chladni patterns on my archtops right from the first one. I wrote it up in my three part plate tuning series in 'American Lutherie' back in '91-92: it should be in the GAL 'Red Book #3? Anyway, I've learned a few things since then which, although they don't change much of what's in the articles, are useful refinements.

As with violins, it's easier to check the 'free' plate modes on archtops by putting the plate on pads with the inside up, like a dish. The glitter runs down toward the center, but tends to stop on node lines. You sprinkle it up slope from where you expect the pattern to be, and it slithers down when you hit the frequency.

On guitars the 'X' mode doesn't seem to be very important; you're mostly working on the 'O' mode. I try to get those to have good shapes, be clearly defined in frequency, and I like to match the top and back 'O' mode frequencies if possible. I generally tune the plates before I cut in the holes or add in the bars. Usually what happens is that you can get decent looking modes at that point, but they get messed up when you cut the holes. Putting in the bars and tuning things gets the top 'O' mode back in shape and frequency (if you ate all of your vegetables). What's supposed to happen than is that the main top and back 'ring' modes come in vey close to the same pitch on the assembled box. The combination of the bridge mass and the down force of the strings drops the top mode pitch so that it's a semitone or a whole tone lower than the back. Sometimes it even works!

I'll see if I can dig out any pictures of this stuff, and I can also scan in the data sheets I keep on this for the guitars I make. I'm going to be pretty busy with a family wedding the next few days, but I'll try to keep track of the thread and give some input when I'm able.

Re: Anyone use Chladini testing for archtops?

PostPosted: Fri Nov 17, 2017 3:19 pm
by Eldon Howe
Beate Ritzert wrote:Chladni figures in a raw archtop plate:

http://www.gitarrebassbau.de/viewtopic. ... 08#p107708

(and please excuse my link into that other forum - i don't know a better way to refer to these).



Thanks Beate, I’ve found resonances near those frequency’s and ones used by flat tops.
The using tea leaves the patterns are not as clear and more grouped in the center.
The back showed the fewest resonances. I can still remove 1.5mm on the back most places.