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Double Bass Rib Bending

#41
Arnold, thanks for that pearl.

Matthew I don't know where I picked up the Diapason term but see it used in my context from time to time. Diapason in my context means "body stop" or top of plate to bridge line. As in " I have a bass with a diapason of 550mm, what should be my neck length?" It might not be correct technically, but some luthiers use it that way.

And it seems we are spelling it differently also.
 
#43
I wondered where I'd come across the word diapason and then remembered seeing it on one of those hundreds of stops on church organs
It's interesting that one of the definitions is " the entire range of an instrument or voice" as that is exactly what is determined by the position of the bridge
The dictionary writers don't seem to be aware of the luthier's specific definition though
di·a·pa·son (d-pzn, -sn)
n.
1. A full, rich outpouring of harmonious sound.
2. The entire range of an instrument or voice.
3. Either of the two principal stops on a pipe organ that form the tonal basis for the entire scale of the instrument.
4. The interval and the consonance of an octave.
5. A standard indication of pitch.
6. A tuning fork.

--------------------------------------------------------------------------------

[Middle English diapasoun, from Latin diapsn, the whole octave, from Greek dia psn (khordn), through all (the notes) : dia, through; see dia- + psn, feminine genitive pl. of ps, every; see pant- in Indo-European roots.]
 
#46
I think I will stick with "body stop" to avoid confusion.

As for the neck heel placement. I am not sure who would want an Eflat neck but here's a method for determining any neck type.

Make a template for the heel curve out of thin template material. (Point to the ceiling with your index finger of your left hand and your thumb pointing right to visualize the shape I am writing about. Somewhere above the point where your index finger starts, is the point where on the supposed fingerboard where either Eflat or D would sound on the G string. So imagine placing the butt of your left hand on the neck heel and stop a note with the second finger (in classic Simandle position). The question of what note you want determines where you place your template to draw and cut the neck heel curve.

I use a D neck but if someone asked for Eflat I could adapt my template.

I went ahead and scanned my template. The numbers are mm from the nut end.

It is interesting how I got the numbers. I used this Stew Mac fret calculator Invalid Link Removed and used a bass guitar (string tension). To get my total string length I needed to kinda switch things around in comparison to a guitar. the "bridge placement" is calculated at the bottom and I used IT for MY string length. I put a number into the scale length and checked if it was close to my string length and by trial and error got the numbers. It is not perfect but checks out pretty well.

Edit, I forgot to say that the mm number from the template came from the 7 or 8th fret. The 7 is D on G string and 8th is Eflat.

The string tension determines how much the string will stretch when pressed down to stop a note. That is why the actual scale length won't work.

Happy Thanksgiving 2007!
 
#47
Ken, tension compensation is important for fretted instruments and this is why the slanted bridge is used, but I don't see that it is that important in a non-fretted instrument, as the player dynamically compensates for this while playing. The Stew-Mac calculator is not doing any tension compensation and the amount of pitch change will be different depending on what strings are use and how high the strings are. So although the D harmonic and stop point are pretty exact, I believe the D "heel-stop" is not an exact point and everyone will use it slightly differently. On the few necks I have set now, a D stop at 1/3 string length seems to work adequately and the heel curve can be adjusted to suit player and thickness of neck.

Reading an old french luthiery tome (Auguste Tolbecque) last night about diapason, the writer used the term several times, but generally in relation to "vibrating length". In the same chapter, he also mentioned a proportion of 5/12 the string length on the neck, and 7/12 string length over the body to describe the proportions of violin family instruments.

I noticed that 4/12 is our D stop, and 6/12 is the octave, so perhaps 5/12 is the simple traditional determinant of the bottom of the neck mortise where the overstand is measured?
 
#48
just want to say that i had no idea when i posted that scrappy little drawing a while back that it would generate this goldmine of interesting thoughts and advice...i feel very priviledged, so my thanks to all of you for sharing your interest and (awesome) knowledge...keep it coming please
 
#49
Matthew Tucker said:
Ken, tension compensation is important for fretted instruments and this is why the slanted bridge is used, but I don't see that it is that important in a non-fretted instrument, as the player dynamically compensates for this while playing. The Stew-Mac calculator is not doing any tension compensation and the amount of pitch change will be different depending on what strings are use and how high the strings are. So although the D harmonic and stop point are pretty exact, I believe the D "heel-stop" is not an exact point and everyone will use it slightly differently. On the few necks I have set now, a D stop at 1/3 string length seems to work adequately and the heel curve can be adjusted to suit player and thickness of neck.

Reading an old french luthiery tome (Auguste Tolbecque) last night about diapason, the writer used the term several times, but generally in relation to "vibrating length". In the same chapter, he also mentioned a proportion of 5/12 the string length on the neck, and 7/12 string length over the body to describe the proportions of violin family instruments.

I noticed that 4/12 is our D stop, and 6/12 is the octave, so perhaps 5/12 is the simple traditional determinant of the bottom of the neck mortise where the overstand is measured?
Click to expand...

Yea but what is the Eflat on the G string? My way answers that question precisely.

Oh how I wish I could read French (and Italian)!:bawl::bawl:

The way I did it tells (near) exactly where the finger stops a given note for a given scale length. I know why a bridge is set back on a guitar and all that...I am using the fret calc to convey the information in a different way than to figure out X% of the string length. Besides, I couldn't seem to figure it out any other way:help:

Ignoring the string-tension-and-pitch-rise-when-pressed issue, Tell me this from your French book :smug::smug: [sarcasm, just kidding], What percent of the string length is Eflat.

Keep in mind that this kind of precision is not necessary and may not even be smart, because the point on the template could vary by several mm itself. It is simply a system so I know what I am getting in a finished instrument. It also clarifies the issue.
 
#50
And one more thing...

String stretch: Play D harmonic on G string then stop it. The Stopped D is about 10mm behind the harmonic (shorter)with high tension strings like Obligato or spiros but much less with gut strings. So the D neck thing could be fudged quite a bit.
I think it is important to have a way to standardize MY way of doing it since I haven't got to play a hundred old-italians.
 
#51
Ken McKay said:
Ignoring the string-tension-and-pitch-rise-when-pressed issue, Tell me this from your French book :smug::smug: [sarcasm, just kidding], What percent of the string length is Eflat.
Click to expand...

Monsieur, c'est - un peu prés - 9/24 de la sillet!

Keep in mind that this kind of precision is not necessary and may not even be smart, because the point on the template could vary by several mm itself
Click to expand...

Yep.

Interestingly, the modern fret calulators use a ratio of 17.718 to lay out standard fretting positions, but in ye olde days when precision wasn't so popular they used the "rule of 18" which resulted in a built-in compensation for pitch rise due to string tension.

So, for a 41.5" string length, the fret calculator will give 20.75" at the octave (true halfway point) whereas the "rule of 18" would give 20.59".

Close enough for a double bass? Its interesting that these "ratios" even though unprecise, could be understood by people with little mathematical knowledge and still be precise enough to produce musical wonders!:D
 
#52
Matthew Tucker said:
Monsieur, c'est - un peu prés - 9/24 de la sillet!



Yep.

Interestingly, the modern fret calulators use a ratio of 17.718 to lay out standard fretting positions, but in ye olde days when precision wasn't so popular they used the "rule of 18" which resulted in a built-in compensation for pitch rise due to string tension.

So, for a 41.5" string length, the fret calculator will give 20.75" at the octave (true halfway point) whereas the "rule of 18" would give 20.59".

Close enough for a double bass? Its interesting that these "ratios" even though unprecise, could be understood by people with little mathematical knowledge and still be precise enough to produce musical wonders!:D
Click to expand...

Thank you sir...that's 17mm longer than the fret calc method for a 1050 string length... a whole finger's width. That does seem to be enough to matter.

Nobody is going to go around and measure this so there is no right answer or best method. I am probably over-thinking for lack of practical knowledge but if a musician says something to me regarding my neck, compared to their ideal, I will know where I stand.
 
#58
Matthew Tucker said:
How do you get 17mm?

My calculator makes it

20.75" - 20.59" = 0.16"
times 25.4 to convert to metric makes it

... about 4mm difference at the octave - or about a quarter of a finger's width - so it seemed close enough for me.

the above is for 105.5mm string length.
Click to expand...



I asked how to calculate where Eflat would be. You gave 9/24 of the total string length. 1050(9)/24 = 394mm. The measure I came up with based on fret placement for a compensated string length was 377, 394-377=17mm.

READ ON!

Now for a real world comparison I measured a bass I have here strung with Obligatos with a string length 1040mm, D stop 342mm from nut, Eflat stop 384mm. Fret calc method would mark D at 336 and Eflat at 374. Uncompensated % method would mark D at 1040(1/3)=346 and Eflat 1040(9/24)= 390.

Conclusion: My overly complicated method is worse at predicting where to place the mark than the % method. :hmm: :o (live and learn).

Discussion: Although my fret calc method is in the ballpark and fairly close, it underestimates the stopped position at these notes on a real bass with Obligatos more than the simple calculated % method underestimates it.
 
#59
What's the difference between the D harmonic and the D stopped, on that bass?

(In truth, the 9/24 measure wasn't actually given in the french book ... I had a guess based on a finer division of the board than 12s, and checked against my fretcalcs, and it seemed close enough to be able to answer your challenge!)
 

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