Pine Bodied Parlors

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Decided to start a separate thread, originally posted in the Parlor thread but realized things might get out of hand and I did not want to monopolize someone's thread. I already went through writing this post but my browser crashed, have to do it all again. My machine is getting uppity about scrips.

Last year I found some thinner pieces of pine that I sanded down and made a bunch of sides and backs out of. I found some quartered cedar fence boards and some quartered pine and made some tops. Built one guitar and this year decided to throw the whole bunch together to see what different arrangements would do to the sound. This was before I was introduced to two fine books, would have done things differently if I started over. But this is what I got.

Original guitar, does not sound bad for what it is but it can use some tweaking.



The four from this year. Two cedar, two pine, tried to make them similar.



Starting from the left #1, the lower bout has thicker braces laid down as compared to #3 which has the lower bout braces vertical. Pine tops, #2 has a three piece back and #4 has a double thickness back also with laid down braces.



Also I had some sides that did not turn out that well, used them and doubled up the sides on #1 and #2



Did some testing of the bodies without bridges. Used a USB mic I bought from a second hand store for $5, works great.



I got the following numbers, pardon me for not using your numbering scheme, I'll get it yet.

Pine double thickness back (#4)
132, 256, , top 241, back 287

Pine three piece back (#2)
124, 241, 300, top 234, back 281

Cedar flat back brace (#1)
123, 275, , top 241, back 247

Cedar tall back brace (#3)
127, 245, 428, top 234, back 221

Then today I redid things as I was told how to capture the plots.

My original numbers for my completed guitar, I got 122, 218, 260 Hz. Funny things are happening as I type, just going to post this and add more in the next one.

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Glad I did that, Adobe Flash crashed in another window. Anyway here is the graph for my completed guitar. I got 122, 218, 260




Just redoing some of these as I was typing in the frequencies before the program crashed.

For the guitar I am building now, #4 the one on the far right, I made up a little jig to string up a couple of the strings and had the bridge floating. I did the measurements and the graphs with some double sided sticky tape holding the bridge on. Just as a recap the frequencies with no bridge was,132, 256, , top 241, back 287.



Response of the top with bridge. 118, 183, 215, 285, 353



Main resonance of the top without the sound hole, 176 Hz, seems I don't have a graph for this one.

Back, 259 Hz and a peak at 353 Hz.



Had a hunch and I tapped the upper back. And there was my 353 Hz.



Which is all well and good, but how does this compare to the box without a bridge, since it comes off so easy... ...maybe another post with the responses side by side.

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Top with bridge. Seem to recall the bridge being 22 grams.



Top with no bridge.



Top no bridge no sound hole.



Back - no bridge.



No bridge - sides. Funny how they have a little step for a block of frequencies, otherwise bot much happening there.



Now the real interesting one would have been the top with no sound hole and comparing the one with the bridge and without the bridge. And then compare that to it with the bridge glued in place. I was working between two computers doing this and going back and forth I seemed to have lost that image. Oh well, next time.

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Redid the top with a bridge with no sound hole, can't edit my last post, I'll put the two in here.

With bridge, top resonance 177 Hz.



Redid the without bridge also, top resonance 192 and 261 Hz.

[DarwinStrings]

G'day Fred, I notice that it looks like you are doing your testing there with the body clamped into that carriage. The carriage will be effectively adding side mass to the body and lowering the frequencies you are trying to look at so you should have a look with the guitar free of that extra mass to get where it really is.

Jim

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I have a jig to act as a tailpiece for the two strings (can't manage playing three yet) and it is attached by the clamps and the back block. I knew it would skew the readings but I was more concerned at finding out which resonance is coming from what part of the body and whether you could attach a bridge to the top with double sided tape and if the box would be anywhere close in response to the top with the bridge glued on. I thought it might be useful if it did for someone who wanted to see what different bridges would do to the top.

In the end I do not think I was consistent enough to say yes or no to that one. I did get the bridge on and strung up with five strings, a set where I stole the E string from. I have not done the frets yet but I tuned to E major and got my slide out. I already had a peak at what this guitar sounds like, absolutely no bass. I also realized I thought I had box #4 and actually it was box #2 with a three piece back. Even just after gluing up the top I felt this one was a dog, maybe why I started with this one first so if I do a dumb mistake to it I won't feel bad about it. Took picture of it and my first build.



You can really see the three pieces of my first guitar. I knew nothing about runout when I started, I got lucky the outside pieces are going the same way. Back to this guitar. I guess I can experiment with shaving braces and see what happens.

[kiwigeo]

G'day Fred, I notice that it looks like you are doing your testing there with the body clamped into that carriage. The carriage will be effectively adding side mass to the body and lowering the frequencies you are trying to look at so you should have a look with the guitar free of that extra mass to get where it really is.

Jim

Fred,

+1 to Jim's comments. Try holding the guitar in playing position. I hang my mike from my workshop ceiling and adjust my chair until mike is right distance from guitar. I'm using a Shure SM57 running into USB port on my laptop. Im running VA as you are.

Cheers Martin

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OK, guitar resting on the back edge and headstock.



Top frequencies, 218, 379



Top resonance 203 Hz



Back, 267, 286, 360



Now I got to look at these to see what I have.

[kiwigeo]

Some of the VA plots look erratic (two top plots in last post) while others are smooth curves as I normally get from my set up. Whats going on there?

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Skip the sunburst one for now, back to my first guitar. It sounds OK but not sure if it is quite right. Took this response of the top.



I have started to put the frequencies in the picture name, much easier to keep track of them. Dips in the frequency has a negative sign before the number. So for the above the composite top response, Lapcat 002 comp 122 -154 219 -254 275 309 550 643, also throwing in the uncoupled top and back resonances. Let me know if I have any of it wrong.

T(1,1)1 = 122 Hz
Fh = 154 Hz
F1 = 199 Hz
T(1,1)2 = 219 Hz
Fb = 257 Hz
T(1,1)3 = 275 Hz
T(2,1)1 = 309 Hz Cross Dipole
T(1,2)1 = 550 Hz Long Dipole
T(2,1)1 = 275 Hz Cross Tripole

There are 3.94 semitones between T(1,1)2 and T(1,1)3.

Now the T(1,1)1 of 122 Hz pretty much lands on B which is 123 Hz and T(1,1)2 of 219 Hz land on A at 220 Hz. I could move the top resonance by adding mass to the sides. Or I could move the top and air resonance down if I shave the top bracing a little. Getting late here, think I will sleep on it.

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Almost had these two ready as gifts for Christmas. Well at least now I have time to measure them.