12-string bridge dimensions?

[peter havriluk]

I realize 12-string fingerboards are wider than 6-strings' fingerboards. But what about string spacing at the bridge? I ran across a 12-string bridge for sale, and its vendor said it was spaced 2 3/16". I assume that the dimension applies to each of 2 sets of strings, which are stepped apart from each other a bit, the width of the array of 12 strings being more than 2 3/16". Is such spacing typical of 12-strings? Or what is 'typical' of 12-strings? Nut width is also involved, and I suspect that the nut width would depend on the width of the entire string array on the bridge. If I had a set of plans in hand for a 12-string, I don't think I'd be asking for advice, but none in hand as I write this.

Thanks very much.

[John Link]

I have built one 12-string in my life. (Everyone loves to play it, no one wants to buy it.) I used the following dimensions:

Nominal scale length: 25.4"

Nut width: 1 7/8"

Bridge string spacing: 2 1/8" each set, with 1/8" offset from front to back, for a total width, center to center, at bridge of 2 1/4". Everyone who plays it says it is easy to play. (All guitars are hard to play as far as I am personally concerned.)

Distance between front and back tier: 1/2"

The "treble" strings were in the front tier, the "bass" in back. Bass tends to get somewhat lost on a 12-string. If I had it to do over I would put the "bass" strings in the front tier to get a steeper angle between them and the saddle to give them a boost, theoretically, at least. There is only so much you can do with ramps.

When it comes to acoustic steel string guitars, "typical" is in the mind of the beholder.

[peter havriluk]

John, thanks for the reply. Now I have some parameters to think about. This is a 'someday' project for me; back when I was a university student I bought a Framus 12-string to learn to play on. That was a non-starter and I sold it after a couple of years when I had an unavoidable offer to go work for the gummint. Still want a 12-string, but I want to build one.

[John Link]

The sound a 12-string makes fascinates me. With properly made fingerboard/neck/relief and set up for close action they are not that much more difficult to play than a 6-string. The one I made was on consignment at the Golden Frets in Carbondale, IL (Little Egypt, according to the locals) for about a year way back when way back was right now. Every time I went in the shop someone was playing BLUEGRASS on it. Needless to say, the sound was not exactly the one associated with traditional bluegrass, but very interesting because those guys, especially Bill Carter - one of the owners and a Little Egypt legend to this day - could really fly with the thing.

Make yourself one. I still have mine and it is still for sale. (Boo hoo.)

I recommend a fully compensated saddle for that bridge, as long as you are going to the trouble. You will not regret the extra work, it is one of the single best investments you can make in 12-string sound. To get it all to work together, you probably need to make the bridge from scratch.

[peter havriluk]

John, I'm not holding a clear picture in my head of what a 'fully compensated saddle' might be, as compared to the compensated saddles on my storebought bridges. Am I being asked to install the saddle in the bridge at more than the usual three degrees off square, more or less? I did a Google search and turned up a long illustrated essay by Paul Hostetter on the subject (http://www.lutherie.net/saddle_angle.html).

[John Link]

I made the saddle below parallel to the front of the bridge. It is 5/16" wide and provided ample room to compensate each string individually - note that the "normal" strings lay in the places you expect them but the four "octave strings" that are an octave higher are compensated differently (the octave E is sgnificantly shorter, the octave A is significantly shorter, the octave D is slightly longer, and the octave G is significantly longer). In the top view I enhanced the shadow to show this better. In the close up quartered view, you can see how it works in 3-d because the less compensated strings protrude towards the front. (The b and e strings are both in their normal places.)

Most 12-strings are nominally compensated for the "normal" strings and the octave strings go along for the ride, most of them out of tune.

I made a flat-topped slug out of ebony that was the height I wanted the finished saddle. Then I took little pieces of piano wire and schooched them back and forth in the approximate pattern for the peaks you see here, then tuned all strings up to normal pitch - in this case full pitch but some tune their 12-strings down a step or two. Then did the final schooching to get true octaves at the 12th fret.

After that it was simply a matter of measuring the distance from the front of the slug to the wire, recording it, and using that to make an ebony saddle to verify my work (this was the first one I ever did). After verification I made the final saddle out of ivory, though bone would be just as good. It was tedious, but the result was worth it. Recording engineers have made positive comments about the scheme.

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12_saddle_2-640.jpg (82.65 KiB) Viewed 1022 times

[ken cierp]

Ditto on the wide fully compensated saddle -- without that feature a 12 string will "always" play out of tune --period!