"Testing" a box for bridge placement

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

  • OK, I went back on my claim I wasnt going to re-read this beast, and at least skimmed it, and it pretty much appears that what I wrote above is redundant. Imagine that!

    But one thing I wanted to add, Siminoff's books are mentioned near the beginning. I have since purchased and read (and in some cases re-read several times) every one of his books. So I thought I would comment on them quickly.

    His book on tap tuning/voicing is not the best, though it has some interesting ideas and many times shows some of his very interesting fixtures, tests and research. I just found it a bit dis-jointed and didnt really think it did much more than raise more questions in my mind. Not to say it was bad or had no use, just saying I cant rave about it and recommend it as being extensive or conclusive.

    On the other hand, his book on Mandolin design and construction would make my "must read" list for anyone who builds small acoustic instruments, and as a bonus contains most of the pertinent tuning/voicing info contained in the prior book. I will warn you, you will probably want to build a Mando after devouring this book.

    • Is that where you learned all the big words. :)

    • No, that took longer......

      But it hasnt helped my typing either.........

      Fumble fingers, thats me! I really can spell somewhat better than it may sometimes appear. Really, I can!

      Edit, again.

  • Granted larger boxes 3" will not work so the tail piece comes into play or you lose frets.

  • And I think you are over thinking it a little. :)

    • "And I think you are over thinking it a little. :)"

      Isnt that the whole point?

      Donovan revived the thread! Donovan revived the thread!

      3 inches then. Hmm. You have no idea what you have done!

      I disagree. I think.......

       

      3 inches...... gonna be a large relative difference between the larger box size range and smaller.....

      But then I think you are focusing on string break angle geometry. So I see your point, but....... Acoustically? Important aspect but its just not as simple as that.

       

      Ok, this thread is about two years old. (No! I am NOT going to re-read this thing!) I have done some (actually quite a bit) more studying that is potentially relevent, but I dont think it has changed my opinions as expressed here too much. But maybe I do look at some things differently. And as I recall we did a bit of supposin'. And keep in mind, CBG is but one little aspect of what I do or what interests me, stringed instrument wise, so------

       

      So heres what I am currently thinking, in a nutshell. Synergy.

      When we were throwing these ideas around I was mostly focused on box size and depth, bridge location, (thanks John Maw! long time no talk!) sound hole location and size and how it all affected output with volume and projection as a primary concern.

      Several areas I have really spent some time studying since then. Theories on tuning and voicing acoustical instruments and Helmholtz theory of resonance especially, have made me look at these things a little differently.

       

      Perhaps the most thought provoking input was from a new aquantance I have made in the field of mountain dulcimer lutherie, who pointed out that in some instruments, both the instrument design and playing style are often developed to use resonance and sustain to make up for limitations in volume and output level......... Hmmm!

       

      There are just so many subtle little relationships that might make up an optimized solution!

      But a wise contributor to this thread also said, "just build the thing and see how it works! Then build another ! and another!" (Hi Micheal! Bet you missed us!)

      Another bit of wise advise from the dude who first started this entire web site.

      "Shutup and learn to play the #&%$#in' thing and none of that *%&&$#^&#^#it will really matter!" (Hi Shane!)

      Yep, I'm bettin' yer gonna regret replying to this one. LOL!

      But then it was 13 pages, and 13 is considered unlucky right?

      I'm still blaming you Donovan, seriosly! :<)

      Best regards to all!

      Mark

  • For me placement of the bridge is 3 inches from the end of any box. This will insure that there is enough tension over the bridge.

  • So you want to be the watcher do ya? LOL!

    MichaelS Country Boy Guitars said:
    Watching... always watching...
  • I know this is an old discussion, but I finally have some good feedback.

    I recently(last week) built a 3-stringer just for the look of the box, not really expecting anything but a good looking toy.

    Much to my suprise, it sounds so good, I have added it to my personal collection. It is a 3 string fretless, and the box is solid spanish cedar. All of my builds are acoustic first, the piezo is just for playing in a crowded area.

    My point is really simple, they all sound good, especially if you tune them DAD/CGC.

    I will definitely need at least a half dozen for myself tuned differently so I can play anything I want just with the slider.

     

  • Watching... always watching...
This reply was deleted.