Replies to This Discussion

Permalink Reply by Roadkill a.k.a. John Maw on December 22, 2010 at 11:28am

Hi Hoov.

 

Very interesting thought you have brought to the thread. I have a couple of questions.

 

Is there a way that you can see of getting golden section (golden ratio, golden mean or any number of names for the same thing) to take account of the characteristics of the individual box? I see from what you said that it might be a way of finding a specified point on the box according to a geometrical formula but how does this help to establish the differing nature of boxes of various designs and patterns?

 

What I have found in testing just a few boxes is how varied the sound characteristics are. The test is not only intended to find the point of best resonance, but to establish how that resonance falls off as the sound source is moved around the box. From what I have seen so far, from a pure resonance point of view placing the sound source at the centre of the box seems to always give the best characteristics. However, on some boxes the sweet spot is well spread, indicating that the bridge could be place in a number of places and still produce a good sound. On others the resonant spot if quite small indicating that correct bridge placement may be more important on a box like this.

 

Mentioned in the original post was the point that a rule takes no account of the vibrating nature of each box but assumes uniformity. A test assumes that there is no uniformity, but is there a way to apply a rule such as golden section in a more flexible way?

Hoov said:

Interesting discussion!

I am a newbie coming from the visual arts and from that realm the Greeks came up with the "Golden Mean" as a way to find dimensional "harmony" in a rectangle.  It works for the rectangular top of a CBG too.  First determine the (inside...unglued) corners of the rectangle.  Use a straightedge to determine the diagonals. Then use a square or compass to strike a line which squares one diagonal and intersects the opposite corner.  (You may want to duplicate your box on a piece of paper to do this rather than poke holes into your box.) The intersection of that line and the diagonal it squares will be a potential sweet spot for your bridge.  Run a line square to the centerline of your box through this point and this line will be the dynamic centerline of your bridge.  Then determine neck length and position it from this sweet spot based on your fretboard (nut to bridge) dimension.

Can't hurt to try it. Pull out your drafting tools (and a tuning fork) and go at it.

The biggest problem that arises with this method is that the folks who decorate the boxes often key off of these same dimensions and you often engage key graphic elements of the box cover as a result of finding this sweet spot. 

Next approach is to extend the bridge base or bracing to engage (activate/vibrate) the "diagonals" or some proportional segment of the line length (space) between them. 

Good fodder for experimentation.

 

 

 

 

 

Permalink Reply by Hoov on December 22, 2010 at 1:19pm

John

The construction does help you to find a potential area on various box top sizes.  Since Box tops differ in size and aspect ratio the construction can help find this proportional sweet spot.   It is similar to finding a harmonic on a guitar string.  If you can see the fretboard markings it is easier to find the harmonic,  if you have no markings it is more difficult and you may take longer to find the spot.

But as you said there are many factors which influence the performance of the box as a vibrating, resonating, surface.  Obviously a gometric construction can't address those.  That is where testing has merit in the process. 

Though the concern I have about all of these methods is that once we have added the rest of our hardware to a box and cut sound holes it will can change the way the top resonates as well.  Perhaps we should seek a bridge position after all that work is done though that backwards approach creates a significant set of challenges.  

 

 

 

 

 

John H. Maw said:

Hi Hoov.

 

Very interesting thought you have brought to the thread. I have a couple of questions.

 

Is there a way that you can see of getting golden section (golden ratio, golden mean or any number of names for the same thing) to take account of the characteristics of the individual box? I see from what you said that it might be a way of finding a specified point on the box according to a geometrical formula but how does this help to establish the differing nature of boxes of various designs and patterns?

 

What I have found in testing just a few boxes is how varied the sound characteristics are. The test is not only intended to find the point of best resonance, but to establish how that resonance falls off as the sound source is moved around the box. From what I have seen so far, from a pure resonance point of view placing the sound source at the centre of the box seems to always give the best characteristics. However, on some boxes the sweet spot is well spread, indicating that the bridge could be place in a number of places and still produce a good sound. On others the resonant spot if quite small indicating that correct bridge placement may be more important on a box like this.

 

Mentioned in the original post was the point that a rule takes no account of the vibrating nature of each box but assumes uniformity. A test assumes that there is no uniformity, but is there a way to apply a rule such as golden section in a more flexible way?

Hoov said:

Interesting discussion!

I am a newbie coming from the visual arts and from that realm the Greeks came up with the "Golden Mean" as a way to find dimensional "harmony" in a rectangle.  It works for the rectangular top of a CBG too.  First determine the (inside...unglued) corners of the rectangle.  Use a straightedge to determine the diagonals. Then use a square or compass to strike a line which squares one diagonal and intersects the opposite corner.  (You may want to duplicate your box on a piece of paper to do this rather than poke holes into your box.) The intersection of that line and the diagonal it squares will be a potential sweet spot for your bridge.  Run a line square to the centerline of your box through this point and this line will be the dynamic centerline of your bridge.  Then determine neck length and position it from this sweet spot based on your fretboard (nut to bridge) dimension.

Can't hurt to try it. Pull out your drafting tools (and a tuning fork) and go at it.

The biggest problem that arises with this method is that the folks who decorate the boxes often key off of these same dimensions and you often engage key graphic elements of the box cover as a result of finding this sweet spot. 

Next approach is to extend the bridge base or bracing to engage (activate/vibrate) the "diagonals" or some proportional segment of the line length (space) between them. 

Good fodder for experimentation.

 

 

 

 

 

Permalink Reply by Roadkill a.k.a. John Maw on December 22, 2010 at 3:09pm

Hi Hoov.

 

Thanks for explaining. I think I see the point that you are making about the proportions, but the difference between a string and a cigar box is that a string has a very simple structure in the sense that as long as it is made properly it should be uniform along its section. A cigar box is made of a much more complex concoction of pieces of wood, which itself is variable. Some of the wood may be ply and some solid, it will be assembled very cheaply with inconsistently glued joints. Many of them are stamped with makers logos and have labels on. All in all that make the behaviour of a box much harder to predict than that of a string.

 

A couple of post back I think that I did mention that I would retest after cutting sound holes and fitting bracing. I intend not to finalise the cutting of the tail end of the neck until that point in the making. It may all be a waste of time or even counterproductive, but somehow I doubt it. My feeling is that even though this may not get the bridge in the absolute best place, on balance it is likely to get it nearer than without testing. On top of that it is both easy, quick and cheap to do. On that basis why wouldn't you?

Hoov said:

John

The construction does help you to find a potential area on various box top sizes.  Since Box tops differ in size and aspect ratio the construction can help find this proportional sweet spot.   It is similar to finding a harmonic on a guitar string.  If you can see the fretboard markings it is easier to find the harmonic,  if you have no markings it is more difficult and you may take longer to find the spot.

But as you said there are many factors which influence the performance of the box as a vibrating, resonating, surface.  Obviously a gometric construction can't address those.  That is where testing has merit in the process. 

Though the concern I have about all of these methods is that once we have added the rest of our hardware to a box and cut sound holes it will can change the way the top resonates as well.  Perhaps we should seek a bridge position after all that work is done though that backwards approach creates a significant set of challenges.  

Permalink Reply by Hoov on December 23, 2010 at 1:11pm

Whatever floats your boat.

BTW

Why don't you post a video illustrating your methods.

 

BTW

Have you tried using the fork atop your intended bridge?

That is a variable you haven't addressed but is apparently as huge an area of concern as all others. A bridge redistributes the force and vibrations accross your box top and therefore will impact the tonal results.  How large should it be and should it be flat or footed. Your tuning fork touches only one very small spot on a box top?   Is that adequate to test accurately? Shouldn't it activate the box top through the intended bridge that is 1.5 to 2.5 inches wide?

These are serious questions but are posed with tongue in cheek.

We all need to learn as much as we can about the craft and use the methods that bring us the results we seek.

Follow your path to the source of your satisfaction.

 

 

 

 

 

John H. Maw said:

Hi Hoov.

 

Thanks for explaining. I think I see the point that you are making about the proportions, but the difference between a string and a cigar box is that a string has a very simple structure in the sense that as long as it is made properly it should be uniform along its section. A cigar box is made of a much more complex concoction of pieces of wood, which itself is variable. Some of the wood may be ply and some solid, it will be assembled very cheaply with inconsistently glued joints. Many of them are stamped with makers logos and have labels on. All in all that make the behaviour of a box much harder to predict than that of a string.

 

A couple of post back I think that I did mention that I would retest after cutting sound holes and fitting bracing. I intend not to finalise the cutting of the tail end of the neck until that point in the making. It may all be a waste of time or even counterproductive, but somehow I doubt it. My feeling is that even though this may not get the bridge in the absolute best place, on balance it is likely to get it nearer than without testing. On top of that it is both easy, quick and cheap to do. On that basis why wouldn't you?

Hoov said:

John

The construction does help you to find a potential area on various box top sizes.  Since Box tops differ in size and aspect ratio the construction can help find this proportional sweet spot.   It is similar to finding a harmonic on a guitar string.  If you can see the fretboard markings it is easier to find the harmonic,  if you have no markings it is more difficult and you may take longer to find the spot.

But as you said there are many factors which influence the performance of the box as a vibrating, resonating, surface.  Obviously a gometric construction can't address those.  That is where testing has merit in the process. 

Though the concern I have about all of these methods is that once we have added the rest of our hardware to a box and cut sound holes it will can change the way the top resonates as well.  Perhaps we should seek a bridge position after all that work is done though that backwards approach creates a significant set of challenges.  

Permalink Reply by Roadkill a.k.a. John Maw on December 23, 2010 at 1:28pm

Hi Hoov.

 

Good point. If you have a look at my third post on this issue I think that I did introduce the idea about using a bridge or at least a suitable substitute. What I haven't worked out is a way of reproducing the pressure of the other two or three strings on the bridge at the same time. Possibly a weight might be useful. Equally possibly this is making the test too cumbersome to be appealing to most people. However it is done, the test is never going to be perfect, but it may still be useful, although that has yet to be established with any certainty.

Hoov said:

Whatever floats your boat.

BTW

Why don't you post a video illustrating your methods.

 

BTW

Have you tried using the fork atop your intended bridge?

That is a variable you haven't addressed but is apparently as huge an area of concern as all others. A bridge redistributes the force and vibrations accross your box top and therefore will impact the tonal results.  How large should it be and should it be flat or footed. Your tuning fork touches only one very small spot on a box top?   Is that adequate to test accurately? Shouldn't it activate the box top through the intended bridge that is 1.5 to 2.5 inches wide?

These are serious questions but are posed with tongue in cheek.

We all need to learn as much as we can about the craft and use the methods that bring us the results we seek.

Follow your path to the source of your satisfaction.

Permalink Reply by Tim Gale on January 17, 2011 at 7:24am

I have read through this discussion and find it very interesting and informative.  I think the idea of using a tuning fork is something I need to try.  The one thought I had is are you using a tuning fork relative to the eventual tuning you intend for that guitar?  If you are going to tune to an open G, do you use a G tuning fork?  Does it matter?  You would think that different boxes might resonate better to a different note.  Maybe this could be used also to decide what tuning will work best for a particular box, or maybe different tunings would sound better at different bridge placement.  Guess I need to get some tuning forks now...

Permalink Reply by Roadkill a.k.a. John Maw on January 17, 2011 at 12:09pm

Hi Tim.

 

I have only used an A tuning fork because that's what I had already (used to tune harpsichords) but I think I have a C fork somewhere, so maybe the first step would be to try that as well and see if the behaviour is the same. Incidentally, I got another box a few days ago (Bering Casinos) and the most resonant point was right on the edge where it joins the side. Most unexpected.

 

On reading your message my first thought was that it shouldn't matter because we are going to play almost every note and therefore every note should sound as good as the others. Second thought was that maybe it does make more sense with CBGs because they use open tuning and most playing will probably play in only that key to which the instrument is tuned. Third thought is that some people will retune often if needed to fit in with other musicians (I retune when following online lessons such as the ones from Keni Lee). So I don't know but it is an interesting idea. I must see if I can find that C tuning fork now.

 

Cheers

Tim Gale said:

I have read through this discussion and find it very interesting and informative.  I think the idea of using a tuning fork is something I need to try.  The one thought I had is are you using a tuning fork relative to the eventual tuning you intend for that guitar?  If you are going to tune to an open G, do you use a G tuning fork?  Does it matter?  You would think that different boxes might resonate better to a different note.  Maybe this could be used also to decide what tuning will work best for a particular box, or maybe different tunings would sound better at different bridge placement.  Guess I need to get some tuning forks now...

Permalink Reply by Roadkill a.k.a. John Maw on January 18, 2011 at 12:05pm

I found the C tuning fork and have tried it on five boxes of various sizes and proportions. The C fork gave similar but not identical results. One box in particular seems very sensitive to placement with the A tuning fork but not as much with the higher C. Incidentally I did the tests with and without a substitute bridge. It didn't make that much difference and the results were similar on all boxes. Not sure what conclusions to draw from this.

Permalink Reply by Tim Gale on January 18, 2011 at 1:31pm

I don't know what this all means either.  I guess what I would do is set up a jig where you could get a box done except for the neck(bracing, soundholes, etc) and string it up with your jig so that you can vary the the placement of the bridge and nut.  Then you could try different bridge placements and still adjust the nut to fit the scale.  It would be interesting to see how this would compare to the tuning fork testing you are doing now.  Keep posting what you find out.

John Maw said:

I found the C tuning fork and have tried it on five boxes of various sizes and proportions. The C fork gave similar but not identical results. One box in particular seems very sensitive to placement with the A tuning fork but not as much with the higher C. Incidentally I did the tests with and without a substitute bridge. It didn't make that much difference and the results were similar on all boxes. Not sure what conclusions to draw from this.

Permalink Reply by Roadkill a.k.a. John Maw on January 18, 2011 at 2:11pm

Hang on a minute Tim. It sounds as if you are volunteering me to do this. That's much more work than I had in mind when I came up with an idea for a quick and simple resonance test. Seriously though, that would be a very good way to establish the position, but I think it will take a keener or more prolific maker than me to put it into practice. Great idea though.

Tim Gale said:

I don't know what this all means either.  I guess what I would do is set up a jig where you could get a box done except for the neck(bracing, soundholes, etc) and string it up with your jig so that you can vary the the placement of the bridge and nut.  Then you could try different bridge placements and still adjust the nut to fit the scale.  It would be interesting to see how this would compare to the tuning fork testing you are doing now.  Keep posting what you find out.

Permalink Reply by Tim Gale on January 18, 2011 at 5:18pm

I was hoping :)

John Maw said:

Hang on a minute Tim. It sounds as if you are volunteering me to do this. That's much more work than I had in mind when I came up with an idea for a quick and simple resonance test. Seriously though, that would be a very good way to establish the position, but I think it will take a keener or more prolific maker than me to put it into practice. Great idea though.

Tim Gale said:

I don't know what this all means either.  I guess what I would do is set up a jig where you could get a box done except for the neck(bracing, soundholes, etc) and string it up with your jig so that you can vary the the placement of the bridge and nut.  Then you could try different bridge placements and still adjust the nut to fit the scale.  It would be interesting to see how this would compare to the tuning fork testing you are doing now.  Keep posting what you find out.

Permalink Reply by Chuck Dubman on January 19, 2011 at 9:12pm

Build a tester, similar to a diddley-bow.  I took a 3 foot length of 2 x 8 and screwed a couple of raised blocks to the ends.  One block was drilled through, 3/32" bit, to act as a tailpiece, the other was drilled to accept the largest eyebolt / tuner I had available.  Boxes (or resonator bowls) get tested for sound and bridge placement by placing them under the string with a 2" piece of thin scrapwood acting as a floating bridge.  You'll find out very fast what works.  As per exact placement of a cigar box bridge, without exception, dead center puts out by far the loudest and the best sound.  Any deviation thereof is purely for looks.  Potential loss of volume is why we have amplifiers, anyway.

 

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