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need help figuring out compensation

PostPosted: Tue Oct 24, 2017 10:07 pm
by Matthew Lau
Dear Mimf,

I'm workign on an acoustic bass guitar, but have trouble figuring out the compensation.

Could you guys help?

I tried using the liutaiomottolla compensation calculator, but am probably doing things wrong.
Parameters keep shifting when I change tabs.

I'll be building a 4-string acoustic bass guitar, 34" scale, Thomastik Acousticore strings
E 41.2 Hz 26.5 lb/in .086 in dia 0.186" action at 12th fret 34 in scale
A 55 Hz 29.2 lb/in .086 in dia 0.165" action at 12th fret 34 in scale
B 73.416 Hz 27.3.5 lb/in .053 in dia 0.135" action at 12th fret 34 in scale
G 97.999 Hz 26.5 lb/in .041 in dia 0.12" action at 12th fret 34 in scale

nylon core

I'm pretty new to this, so am probably doing stuff wrong

Re: need help figuring out compensation

PostPosted: Wed Oct 25, 2017 1:32 am
by Peter Wilcox
For starters, your string diameter is wrong for the A string. But what the calculator wants is the core diameter for the strings, which is unknown (to me.) The calculations seem to be heavily dependent on the core material and the core diameter.

If I use the default parameters for a 34" scale with nylon floss cores, I get the compensation of a straight saddle of 0.0518" for the G string to 0.097" for the E. I'd think for that small amount you could just shape the saddle without having to angle the slot.

Re: need help figuring out compensation

PostPosted: Wed Oct 25, 2017 2:04 pm
by Matthew Lau
Thanks!

I've built a few kits in the past and used plans, but this is my first "new" design (ripping off of Luittoto's Tinozza bass, but smaller body, different bridge, etc).

Re: need help figuring out compensation

PostPosted: Wed Oct 25, 2017 2:04 pm
by Matthew Lau
btw, Peter, I just realized that you're in California.

What part? Sometime, I'd like to get away from work and pay you a visit.

Re: need help figuring out compensation

PostPosted: Thu Oct 26, 2017 12:17 pm
by Peter Wilcox
Hi Matthew - I'm in Janesville, about 60 miles north of Reno on 395. Where are you located?

Re: need help figuring out compensation

PostPosted: Thu Oct 26, 2017 3:12 pm
by Jeff Highland
I built a bass a few years back using savarez nylon core strings. Compensation requirements were minimal, and pretty well straight across.
The nylon core has a much lower modulus of elasticity than steel so the tension does not rise as much when fretting.

I would suggest you try the strings on an electric bass with adjustable saddles and set it up for good intonation, then measure the result. Calculation alone will not get you there.

Re: need help figuring out compensation

PostPosted: Thu Oct 26, 2017 4:51 pm
by Jeff Highland
I went back and measured what I have on my bass with the Savarez strings.
I would expect that what peter wilcox suggested would be very close