Regarding measuring for bridge/saddle placement:
In kits, Martin recommends adding 1/10" to the scale length and placing the near (sound hole-side) High-E end, edge of the saddle slot at that measurement.
Stewmac, on the other hand, recommends adding 7/64" (about the same amount) to the scale length, but they say to place the middle of the saddle slot between the D-G strings at that measurement.
Clearly, they agree on the basic amount to add, but the difference in measurement point throws that agreement all out the window.
Martin's edge-of saddle procedure puts the bridge farther from the sound hole, increasing compensation, while Stewmac's center-of-saddle-slot procedure puts the bridge closer, decreasing compensation.
I'm curious -- why the difference? Is it, as Paul Hostetter said on his site (lutherie.net/saddle_angle.html) a problem with Martin using an outdated system? Or is Stewmac way off?
I'm genuinely wanting to find out if either of these is closer to "correct," all other things being equal on the guitar.
Thanks in advance --Hoping for clarification
Oops. I just realized the Healdsburg fest is next weekend. If you guys who could address this question are busy, that's okay! Have a great time in Healdsburg.
My experience tells me it's better to follow the Martin method. Both methods may work though. With a thick saddle bone I'd probably go with Stewmac.
I rather think it depends on what strings will be used on the instrument. Intonation is affected by string gauge, materials and manufacture and anything you do in the initial manufacture will need to be modified when the end user installs his favourite strings. Perhaps there's a best-guess compromise, but I have yet to find it.
I agree - lighter strings need more compensation. We're dealing with very small measurements, too, and not everyone can even hear such small differences in pitch. According to Mike Doolin, a 15/1000-inch change in string length results in a one cent (1% of a half-tone) change in pitch.
In working on this book revision, I'm tying to figure out just how deep I should go into this subject, since it's for novice builders who are building kit acoustic guitars. Since the two major kit providers offer different methods of measuring, I thought I'd ask for opinions. Thanks --
That's interesting. I haven't measured a factory Martin recently. Ever, in fact. It would not be surprising to discover that the Martin "Handy Hints" booklet was completely incorrect about the correct measurement. I'm only talking about Martin's measurement (stated in their kit building booklet) to the "near" edge of the saddle slot, while Stewmac goes to the center of the saddle slot between D & G strings. I tend to favor Stewmac's, myself, but I don't want to mislead anybody. It's not a whole lot of difference, but to someone with acute tonal hearing, it could make a world of difference. I don't have that hearing acuity anymore. Wish I did. Now, I think I'll find a Martin or two and measure them. (Paul Hostetter, in an email, said to me that both of them have a much too shallow slot angle.) - Thanks -
Thanks David -- that is helpful and good information. The angle-setting from high and low E strings is concise and clear. Could be helpful for kit builders, but only if they have the facilities to cut their own saddle slot. (Or the guts to simply angle the whole bridge. Ha-- That would make the guitar a great conversation piece!)
Ps. I share your ire about Otto (Otto Crect) -- he's an authoritarian dictator with little empathy for what we want to express. He can't be taught anything by us proles.
Bill, One thing I've run into and don't hear discussed much is string hieght and bridge rotation.
If you layout saddle location on an unstrung instrument with a top/bridge/saddle that rotates significantly under tension, the top of the saddle, sometimes moves toward the nut significantly but a low saddle on a shaved bridge almost none.
Once I did the trig and found something like .035" for a 2 degree rotation with 1/2" string height off the top.
It's something I started to take into account when routing slots on instruments with high string heights and/or weak tops.
I had a good quality factory instrument this morning with this problem. It has a 3/8"bridge that puts the strings 9/16" above the top. the neck is a bit overset. If I measure the slot location unstrung it should be ok but strung up, even with low action, the break points need to be moved back to the bone chipping back edge to be tolerable.
I just used an online calculator and it works out to .o15" for a 2 degree rotation. Throw in a little saddle lean and you can be out of range.
Okay, that's new wrinkle. I wonder if the kit manufacturers, who are basically trying to repeat standard bridge/saddle/nut designs, take that into account in their calculations? I know I never thought of it.
That's a good thing to know, for sure. I'm going to hope that that's all considered and taken care of in the kit designs for the newbie builders I'm writing for. Thanks David --
Ps. That .015" is one more cent, plus or minus, thrown into the mix. I imagine, with a tall saddle, a tad high action and a saddle slot on too shallow an angle, it would be possible to remove most of the effect of compensation.