Anyone know how to measure for a compensated bridge?

[Eric Banjitar]

Hey everybody!

Here is a challenge for ya.  I would like to build a compensated 6-string banjo bridge to achieve perfect intonation on my instrument. My question is what are the exact measurements of the set-backs?  I am using super slinky 9s on a warmoth conversion (24-3/4") neck. The bridge floats accross the head of the instrument much like an archtop bridge.

As I understand things, correct intonation is a product of the scale length and the string thickness.  This has to do with the frquency of the strings moving at a given length and is complicated by the thickness of the strings. Thicker strings need a longer distance, slightly.  Thinner strings need to be slightly shorter.

I would imagine that there is a formula for figuring this.  Can anyone help? :icon_scratch:

 

[bagman67]

My suspicion is that a bridge of the thickness of a tradtional banjo bridge may not provide enough range for you to compensate the saddles enough to provide something like "correct" intonation, which is at best a compromise anyway.  But:  if you angle the bridge, you may be on to something.  Treble end closer to the neck, bass closer to the tailpiece. 

Maybe you could use this as a model, bearing in mind that this contemplates a very thin fifth string for traditional five-string banjo, rather than a heavier string as you move from right to left.

http://www.stewmac.com/shop/Bridges,_tailpieces/Banjo_bridges/5-String_Compensated_Banjo_Bridge.html?actn=100101&xst=3&xsr=25252

 

[Eric Banjitar]

My original idea was to make the bridge kind of a combination of the two pictures above. I have some 4/4" maple and 3/16" rosewood. I thought that I would build a standard banjo bridge just wider for the sixth string and thicker to allow for the setback of the compensation.  The bridge would then be carved with a dremmel to give the "Z" type relief. I just dont know how far back to set the 6th and third strings. My guess is that the 2nd and 5th strings should be at the scale length measurement, the first and fourth slightly forward (1/16-1/8") and the 6th and third slightly back from the others. Is there a precise measurment formula? Does it matter that much?  :help:

 

[bagman67]

Is there a precise measurment formula? Does it matter that much?  :help:

I think the fact that there are so many different string gauges out there renders any universal formula unlikely - hence the proliferation of individually adjustable saddles in electric guitar land.  For acoustics and amplified archtops with single-piece saddles, the best you can hope for is to make it better than a straight line. On that count, the approach you're suggesting above sounds pretty good to me.

If you're planning on using the same gauge of strings on your banjitar as you use on any regular electric you have (and assuming the same scale length, and further assuming the standard electric actually has its intonation set correctly), try measuring the distance from nut to saddle on each string and then reproducing that. 

Finally, recognize that with a non-attached bridge on the banjitar, you'll want to check the bridge distance regularly - like at least every time you restring, and maybe more often than that.

Hope this helps -

Bagman

 

[Eric Banjitar]

Thanks Bagman!

This did help, if for nothing else it has boosted my confidence that I was on the right track.

Is there a precise measurment formula? Does it matter that much?  :help:

I think the fact that there are so many different string gauges out there renders any universal formula unlikely - hence the proliferation of individually adjustable saddles in electric guitar land.  For acoustics and amplified archtops with single-piece saddles, the best you can hope for is to make it better than a straight line. On that count, the approach you're suggesting above sounds pretty good to me.

If you're planning on using the same gauge of strings on your banjitar as you use on any regular electric you have (and assuming the same scale length, and further assuming the standard electric actually has its intonation set correctly), try measuring the distance from nut to saddle on each string and then reproducing that. 

Finally, recognize that with a non-attached bridge on the banjitar, you'll want to check the bridge distance regularly - like at least every time you restring, and maybe more often than that.

Hope this helps -

Bagman

I would think that one of our more physics, musicologists-type members would be able to create a formula that would give perfect intonation distances for a bridge given the scale length and the string thickness/type. Anyone?????????

Oh, and by the way, I feel lucky to be able to the pick the brains of all of you (thanks again Bagman) with your help, support and hummor, I was able to build a unique functional quality instrument.  I could not have done this wihtout your help. HELP!