I've been searching through the articles on this site for information on selecting the position where the bridge should be. Obviously on an unfretted instrument you can move the bridge and experiment, but on a fretted guitar, once the frets are on and the neck is fixed that's it. You have committed yourself.

 

So is there any way to know on a box for box basis (not using formulas because I'm pretty sure that they are worthless unless you always use identical boxes) where the bridge should be to get the best results?

 

Now I've already done some test, but I don't know if they are the work of a visionary (don't laugh) or a pointless waste of time (odds on the latter). I was thinking that as far as the box is concerned it gets most of the string vibration through the bridge. If you want to simulate vibrations coming from the bridge can you use something else that will transmit vibrations and see (or rather hear) how they sound and make a choice based on that. I found a tuning fork and tried it at various places on three boxes that I intend to use soon.

The results from the three were quite different. Not surprisingly all gave the warmest and clearest sound in the centre of the box. The top one gave quite progressive results getting better quite gradually towards the centre. The left hand one was very even across it's width until right near the edge. The right hand one was a surprise as it sounded best right in the middle, tone falling off and getting soft of nasal even an inch away from the motif. Shame as I don't really want to put a bridge right on the motif but my tuning fork test suggests that it may be the best place.

 

So, finally, to the question. Has anyone done any tests - similar or otherwise - that give a good indication of where to put a bridge and that do not rely on ratios or formulas, but take into account the different characteristics of each box?

 

 

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Replies to This Discussion

Hello John, The bridge is at one end of the scale length. The nut or zero fret being the other. For example, if you use a guitar scale length of 25.5 inches, then set the mark at where you want the bridge to be, then measure 25.5 inches to where the nut will be. Take an old yard stick, mark it at 25.5 inches, set one end of the stick at where the bridge will be, the other end will be where the nut will be. Design the whole guitar around those measurements, adding the headstock length, and length beyond the bridge. Example, 6 inches of headstock + 21.5 inches of fret board + 4 inches to bridge, (middle of box), + 4 inches to end of box = overall length. Clear? 

Hi Richard.

 

Thanks for the response.

 

It seems that I may not have expressed myself too well. I understand how to design a guitar of a particular scale length. It goes without saying that for a given scale, if you place the bridge very near the tail end of the box the neck will have to be shorter and if you place the bridge further away from the tail the neck will have to be longer, but that was not my question.

 

The issue is weather anyone has established reliable test to find the best place to put the bridge in order to get the best sound from any particular box. It is a question of getting the most pleasing sound from a box and choosing the bridge placement according to the characteristics of the particular box and not by any generalised formula.

Richard Sanabia said:

Hello John, The bridge is at one end of the scale length. The nut or zero fret being the other. For example, if you use a guitar scale length of 25.5 inches, then set the mark at where you want the bridge to be, then measure 25.5 inches to where the nut will be. Take an old yard stick, mark it at 25.5 inches, set one end of the stick at where the bridge will be, the other end will be where the nut will be. Design the whole guitar around those measurements, adding the headstock length, and length beyond the bridge. Example, 6 inches of headstock + 21.5 inches of fret board + 4 inches to bridge, (middle of box), + 4 inches to end of box = overall length. Clear? 

Honestly, I can resaw a stack of soundboards out of the same board, and each ONE of them will be a bit different. Toss out your math formulas; this depends on the characteristics of each piece of wood. Sorry. You can probably get "good enough" by putting the bridge about 1/4 to 1/3 the length of the box.

You are on the right track in testing each box. I've never used a tuning fork, but that has lots of merit. I just tap it with a pencil's eraser. You might look at "The Art of Tap Tuning: How to Build Great Sound into Instruments" by Roger Simonoff. You can see a few pages online at Amazon and see if he addresses your questions.

Hi Alan.

 

Thanks. Your suggestion about the Roger Simonoff book took me to the Siminoff web site. 

http://www.siminoff.net/pages/siminoff_book_editcorexTAP.html

There looks to be a lot of information there, although for a relative newcomer like me it may take some time to get to grips with most of it.

 

Just as a further test I have tried the same thing but with a piece of wood placed on the box as if it were a bridge and the tuning fork held against that. The results were similar but a little more predictable, particularly on the Padron box where very small changes in position made very noticeable changes in the sound. What is frustrating me now is that it looks as if the Padron box might make a super instrument but only if I put the bridge so that is obscures the makers brand and so spoils the look. They say you can't have everything. In this case it may be true.

 


Alan Roberts said:

Honestly, I can resaw a stack of soundboards out of the same board, and each ONE of them will be a bit different. Toss out your math formulas; this depends on the characteristics of each piece of wood. Sorry. You can probably get "good enough" by putting the bridge about 1/4 to 1/3 the length of the box.

You are on the right track in testing each box. I've never used a tuning fork, but that has lots of merit. I just tap it with a pencil's eraser. You might look at "The Art of Tap Tuning: How to Build Great Sound into Instruments" by Roger Simonoff. You can see a few pages online at Amazon and see if he addresses your questions.

Okay, I understand your question. I place the bridge where the response is best, according to my ears, and experience, and where it needs to be in the final product, and not to any formula or test result. I make mandolins, and where the bridge needs to be is governed by the size of body, type of wood, neck length, and type of sound / F hole used. Each cigar box, even similar ones, sound very different, as do mandolins. Mandolins are fairly predictable, but cigar boxes are very unpredictable. Also, the bracing will affect tone, and volume. One builder said I needed to make 100 mandolins before all factors would be in the best place, according to the type I build. I am on number 43. I learn from each one. Some I've thrown away, some I sell, some I give away, a few I cherish and play everyday. Trust your ears. Give them to other players to test fly, and get feedback. Make a lot of CBGs.

John H. Maw said:

Hi Richard.

 

Thanks for the response.

 

It seems that I may not have expressed myself too well. I understand how to design a guitar of a particular scale length. It goes without saying that for a given scale, if you place the bridge very near the tail end of the box the neck will have to be shorter and if you place the bridge further away from the tail the neck will have to be longer, but that was not my question.

 

The issue is weather anyone has established reliable test to find the best place to put the bridge in order to get the best sound from any particular box. It is a question of getting the most pleasing sound from a box and choosing the bridge placement according to the characteristics of the particular box and not by any generalised formula.

Richard Sanabia said:

Hello John, The bridge is at one end of the scale length. The nut or zero fret being the other. For example, if you use a guitar scale length of 25.5 inches, then set the mark at where you want the bridge to be, then measure 25.5 inches to where the nut will be. Take an old yard stick, mark it at 25.5 inches, set one end of the stick at where the bridge will be, the other end will be where the nut will be. Design the whole guitar around those measurements, adding the headstock length, and length beyond the bridge. Example, 6 inches of headstock + 21.5 inches of fret board + 4 inches to bridge, (middle of box), + 4 inches to end of box = overall length. Clear? 

It would be well worth your time, then, to read the reviews Siminoff got on his tap test book on Amazon. Some people loved it, and an equal number of people felt ripped off. I'm too new at this game to have a personal opinion, but it does raise questions.

 

Jeeze, when I started out on building my first guitar, I thought all the big questions had been answered back in the 18th century. Now I see that a lot of this was no more than educated guess work. I suppose this would be dull, paint-by-numbers sort to thing otherwise.

Oooh! Dibs on your next factory reject! Unless you've shattered the soundboard (I've done that), I bet you toss away stuff better than CBG's I love. Lol.

Richard Sanabia said:

. I am on number 43. I learn from each one. Some I've thrown away, some I sell, some I give away, a few I cherish and play everyday.

Hi Richard.

 

I am very interested in your reply and in particular a couple of points. You said "I place the bridge where the response is best, according to my ears,". That is exactly the sort of method that I am interested in. But how do you test? The point is that once you have made and fitted a fretted neck your bridge placement is determined. You can't change it or the fret spacing is wrong. But you can't play in instrument without a neck (and strings and all the other stuff). So how, in the early stages of making and instrument, do you test? What is the method?

 

The other thing that particularly interests me was that you said "Also, the bracing will affect tone, and volume". This was another thing that I was thinking about. I intend to brace this box. I think I can put in at least most of the bracing before committing myself too much to a bridge position, but the struts were going to be thickest at the bridge position, that being the point of greatest stress on the top. It sounds from what you are saying that it is possible that the "sweet spot" might move (or grow or disappear altogether ;-) once the bracing is in. Is this likely?

 

Many thanks.

 

 

Hi Alan.

 

Don't come the "I'm too new" stuff with me. I've seen the photos of your instruments and jolly marvellous they are too. If you were a veteran of one single and lonely guitar (like me) you could claim that. From where I stand you are a master, so there.

 

If you consider how much they got right in the 18th century it is staggering, and they didn't have resources like CBN in order to help them to compare notes (pun intended) and learn from each other.

Alan Roberts said:

It would be well worth your time, then, to read the reviews Siminoff got on his tap test book on Amazon. Some people loved it, and an equal number of people felt ripped off. I'm too new at this game to have a personal opinion, but it does raise questions.

 

Jeeze, when I started out on building my first guitar, I thought all the big questions had been answered back in the 18th century. Now I see that a lot of this was no more than educated guess work. I suppose this would be dull, paint-by-numbers sort to thing otherwise.

Nothing to test, just finish it, set everything the best you can, and hear how it sounds. Guitar makers will take a big unfinished body, set a candle near the sound hole, rap a knuckle on the back, and HOPEFULLY the candle will blow out. If it doesn't, oh well....... That test doesn't work on a mando, the flame will flicker, as mandolins have a different resonance range, and with a CBG, nuthin'.. Too many variables with CBG materials. Have fun, don't worry about making the next Martin. The experience you gain with each one will allow you to know the final result with each way you brace, and glue up the final box. The thinner the better. The best mandolins I have done are the ones that seem to be on the verge of collapse. The best mandolin I have heard was an old Carlo Sayati built in 1905 of Birch and Poplar. The thing would groan when tuning, but what a sound when played. A SWEET ring and WONDERFUL woody tone. Seemed to weigh a few onces. Eight mandolin strings put great stress on any mandolin. 

John H. Maw said:

Hi Richard.

 

I am very interested in your reply and in particular a couple of points. You said "I place the bridge where the response is best, according to my ears,". That is exactly the sort of method that I am interested in. But how do you test? The point is that once you have made and fitted a fretted neck your bridge placement is determined. You can't change it or the fret spacing is wrong. But you can't play in instrument without a neck (and strings and all the other stuff). So how, in the early stages of making and instrument, do you test? What is the method?

 

The other thing that particularly interests me was that you said "Also, the bracing will affect tone, and volume". This was another thing that I was thinking about. I intend to brace this box. I think I can put in at least most of the bracing before committing myself too much to a bridge position, but the struts were going to be thickest at the bridge position, that being the point of greatest stress on the top. It sounds from what you are saying that it is possible that the "sweet spot" might move (or grow or disappear altogether ;-) once the bracing is in. Is this likely?

 

Many thanks.

 

 

I found the best way to brace a CBG was to use fan bracing, with the center of the fan under where the bridge sits. The bracing holds up the top, and adds a "ring" to the voice. Ladder bracing is a lot easier, but the tone is duller. Keep the braces light. Build upside down, so the box lid is the bottom, that allows you to access the top until you develop your style, and hear how the changes you make affect tone. Don't run the neck against the top, that sounds DULL unless you use a pickup. Try a design like this so the top can vibrate. It ain't traditional, but sounds louder.  This is not a real CB, and the strong Birch top allows me to use it without braces. View looking from the bottom. Sound port is on the side, pointing to the player. It's audible when jamming with others. 

Richard Sanabia said:

Nothing to test, just finish it, set everything the best you can, and hear how it sounds. Guitar makers will take a big unfinished body, set a candle near the sound hole, rap a knuckle on the back, and HOPEFULLY the candle will blow out. If it doesn't, oh well....... That test doesn't work on a mando, the flame will flicker, as mandolins have a different resonance range, and with a CBG, nuthin'.. Too many variables with CBG materials. Have fun, don't worry about making the next Martin. The experience you gain with each one will allow you to know the final result with each way you brace, and glue up the final box. The thinner the better. The best mandolins I have done are the ones that seem to be on the verge of collapse. The best mandolin I have heard was an old Carlo Sayati built in 1905 of Birch and Poplar. The thing would groan when tuning, but what a sound when played. A SWEET ring and WONDERFUL woody tone. Seemed to weigh a few onces. Eight mandolin strings put great stress on any mandolin. 

John H. Maw said:

Hi Richard.

 

I am very interested in your reply and in particular a couple of points. You said "I place the bridge where the response is best, according to my ears,". That is exactly the sort of method that I am interested in. But how do you test? The point is that once you have made and fitted a fretted neck your bridge placement is determined. You can't change it or the fret spacing is wrong. But you can't play in instrument without a neck (and strings and all the other stuff). So how, in the early stages of making and instrument, do you test? What is the method?

 

The other thing that particularly interests me was that you said "Also, the bracing will affect tone, and volume". This was another thing that I was thinking about. I intend to brace this box. I think I can put in at least most of the bracing before committing myself too much to a bridge position, but the struts were going to be thickest at the bridge position, that being the point of greatest stress on the top. It sounds from what you are saying that it is possible that the "sweet spot" might move (or grow or disappear altogether ;-) once the bracing is in. Is this likely?

 

Many thanks.

 

 

Hi Richard.

 

Sorry to keep coming back to this, but I don't understand how you "place the bridge where the response is best, according to my ears," without some form of audible test before the dimensions of the neck and bridge are finalised. For me that is the sticking point and very much the point of the original question. I may be missing something (other than sleep), and I could really do with guidance.

 

Thanks for putting up with my persistent questioning.

Richard Sanabia said:

Nothing to test, just finish it, set everything the best you can, and hear how it sounds. Guitar makers will take a big unfinished body, set a candle near the sound hole, rap a knuckle on the back, and HOPEFULLY the candle will blow out. If it doesn't, oh well....... That test doesn't work on a mando, the flame will flicker, as mandolins have a different resonance range, and with a CBG, nuthin'.. Too many variables with CBG materials. Have fun, don't worry about making the next Martin. The experience you gain with each one will allow you to know the final result with each way you brace, and glue up the final box. The thinner the better. The best mandolins I have done are the ones that seem to be on the verge of collapse. The best mandolin I have heard was an old Carlo Sayati built in 1905 of Birch and Poplar. The thing would groan when tuning, but what a sound when played. A SWEET ring and WONDERFUL woody tone. Seemed to weigh a few onces. Eight mandolin strings put great stress on any mandolin. 

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