D Extension string length calculator

[james condino]

Can anyone give me a quick reference for a string length calculator that will give me a target range for an extension length? In particular, I've got an instrument with a 42" scale that I'd like to add a D extension to. I read in one of the old threads that someone suggested doubling the scale length and then using a calculator to drop down a step from the octave. That sounds ok, but I'd guess that I'll need maybee 1/4" margin of error so I should have an adjustable nut. Any images of E string D extensions are welcome.

I've heard lots of pro / con ideas about D extensions. I generally tune DADG about 75% of the time and use a big thick Spiro Stark, so I'm used to the tuning and like it. I'd like to see how the added length responds. If in the end, I find it overkill, I'll remove it, but for now, I'd like to give it a try and get it out of my head....

On a vague side note, I've had conversations with one of the big tuner companies and there is an adjustable single double bass machine in the prototype stage right now that will work like the cam activated machines available for slab basses that allow you to flick a lever and the string drops down a whole step. We'll see how it works in the real world and if they ever release it for production.

Thanks,

j.

[bejoyous]

I use the exact same setup - DADG with a short extension to a low-B with a capo at Low-C and a Spiro Stark E string. The low notes with the Spiro Stark sound great. One time, the vibrations even knocked some art off my wall.

I don't think there is a difference in tension if you tune the string to low-D at the nut or have a low-C extension because it would still be a D at the nut.

Also, I redid my extension to have a low-B so I could adjust where the low-C capo is located just in case I get a new bridge cut or whatever. until then, I have a low-B which is nice to use once or twice a year. So, if you have room enough between the nut and the scroll, you might want to think of doing the same. I used the capos from Robobass. They are about $100 each and fairly easy to install. (Easier for you than me, I'm sure)

I used this fret calculator as found in this thread.

Using the 1/17 rule also works as in post #9 of my alternate extension solution thread.

[Dr Rod]

Originally Posted by bejoyous

I use the exact same setup - DADG with a short extension to a low-B with a capo at Low-C and a Spiro Stark E string. The low notes with the Spiro Stark sound great. One time, the vibrations even knocked some art off my wall.

I don't think there is a difference in tension if you tune the string to low-D at the nut or have a low-C extension because it would still be a D at the nut.

Also, I redid my extension to have a low-B so I could adjust where the low-C capo is located just in case I get a new bridge cut or whatever. until then, I have a low-B which is nice to use once or twice a year. So, if you have room enough between the nut and the scroll, you might want to think of doing the same. I used the capos from Robobass. They are about $100 each and fairly easy to install. (Easier for you than me, I'm sure)

I used this fret calculator as found in this thread.

Using the 1/17 rule also works as in post #9 of my alternate extension solution thread.

my method may be unorthodox but it works for me, you will have to adjust and tune as with any method.

if you have a low open D, then the middle of your string when you have the extension will be the D near the neck, so you find that D and mark the fingerboard with a pencil, then measure the distance between this middle D and the bridge, and this distance should be the same as between this middle D and the open D (basically to know the length of the extension you would do distance from middle D to bridge, minus distance from nut to middle D)

[bejoyous]

Using the fret calculator:

I used mm as they would probably be easier and more accurate to use than inches (ex. 43 and 35/64")
-if the string length is exactly 42" this converts to 1066.8 mm. (42" x 2.52 = 1066.8mm)
-double the SL - 2133.6
-put 24 in for the number of frets.

Using DADG tuning:
The D (fret 12) would be at 1066.8mm.
Db (fret 11) would be at 1134mm (1066.8mm + 67.2mm)
C (fret 10) would be at 1205.2mm (1134mm + 71.2mm)
and if you put on a low-B (fret 9), it would be at 1280.6mm (1205.2mm + 75.4mm)

I don't think the 1/17 method is quite accurate enough come to think of it.

May the fourths be with you.

[CPike]

Originally Posted by james condino

Can anyone give me a quick reference for a string length calculator that will give me a target range for an extension length?

The 1/17 method will get you very close to the ballpark, and yes and adjustable nut is a good idea.

Originally Posted by james condino

I've had conversations with one of the big tuner companies and there is an adjustable single double bass machine in the prototype stage right now that will work like the cam activated machines available for slab basses that allow you to flick a lever and the string drops down a whole step. We'll see how it works in the real world and if they ever release it for production.

Do you mean like those "hip-shot" doohickeys? Oh my, that's a scary thought having a DB string detune that far that fast... Unlike fixed-bridge slabs, when you increase/decrease tension on one side of the instrument, the whole assembly reacts and compensates by doing the reverse on the opposite side. Most of us have tuned down to a D "on the fly" only to realize our G strings have gone sharp. I seriously doubt any cam mechanism, no matter how accurate, will be able to prevent this from happening.
cdp

[robobass]

Originally Posted by CPike

The 1/17 method will get you very close to the ballpark, and yes and adjustable nut is a good idea.


Do you mean like those "hip-shot" doohickeys? Oh my, that's a scary thought having a DB string detune that far that fast... Unlike fixed-bridge slabs, when you increase/decrease tension on one side of the instrument, the whole assembly reacts and compensates by doing the reverse on the opposite side. Most of us have tuned down to a D "on the fly" only to realize our G strings have gone sharp. I seriously doubt any cam mechanism, no matter how accurate, will be able to prevent this from happening.
cdp

There was an something long ago called the "ManCee extension" or something similiar. There was a cam in the pegbox under the E with a lever that dropped it to C, and there were also cams under the other strings which were operated by a second lever, allowing compensation for the change in tension, keeping the upper strings in tune. Also, at least in the picture it looked pretty lightweight and low key. Seemed like a great idea, but I never actually saw one. Someone out there must know something about it.

[CPike]

http://www.kean.edu/~ascelba/old/mai...ed/tononi.html

That looks like fun... (not)

[robobass]

Originally Posted by CPike

http://www.kean.edu/~ascelba/old/mai...ed/tononi.html

That looks like fun... (not)

Yeah, that's harsh. I'm pretty sure though that he later refined the design into something more elegant and not requiring scroll cutting.

[james condino]

I promised not to run my trap too much about the prototype doohickie in the works now, so I'll just leave it at the idea that some folks with good production tooling technology and enough other sales going so that they can waste a lot more time and money than I can are actively working on the idea.....

I've got one of Rob's capos; it is much nicer than I expected for a very fair price! Everything is in pieces on the workbench right now, so I'll likely have a progress report by the end of the week....love that removable neck!!!!

I'm leaning heavily towards one of the stubby, whole step extensions right now; one that does not go all the way to the scroll ( don't have one!!!) From looking at other's designs and doing a few mock-ups, it looks like I'll need to have some kind of counterbalance that spans both cheeks of the pegbox, or else everything will rotate inwards and collapse.

Either way, I'll get it worked out soon and you can likely guarantee that it will be bold , functional, and won't look like the one on your grandma's bass!

Thanks for all of the info and help; keep it going if there is more available. That ManCee device doesn't stand out nearly as much as the full length side cracks...

j.

[Ken McKay]

Originally Posted by james condino

Can anyone give me a quick reference for a string length calculator that will give me a target range for an extension length? In particular, I've got an instrument with a 42" scale that I'd like to add a D extension to. I read in one of the old threads that someone suggested doubling the scale length and then using a calculator to drop down a step from the octave. That sounds ok, but I'd guess that I'll need maybee 1/4" margin of error so I should have an adjustable nut. Any images of E string D extensions are welcome.

I've heard lots of pro / con ideas about D extensions. I generally tune DADG about 75% of the time and use a big thick Spiro Stark, so I'm used to the tuning and like it. I'd like to see how the added length responds. If in the end, I find it overkill, I'll remove it, but for now, I'd like to give it a try and get it out of my head....

On a vague side note, I've had conversations with one of the big tuner companies and there is an adjustable single double bass machine in the prototype stage right now that will work like the cam activated machines available for slab basses that allow you to flick a lever and the string drops down a whole step. We'll see how it works in the real world and if they ever release it for production.

Thanks,

j.

Ray Mattola's got the info on is site.

d = s – (s / (2 ^ (n / 12)))
n = stop position.
d is the distance calculated in inches
s = scale length
For a 42 inch scale d = 5.14 inches behind the nut.

[iiipopes]

Another way to comput it: the 2^(1/12) constant is (rounded off) 1.0594631. So, take your scale length on your low E string, multiply it by the constant to get Eb, again to get D, again to get Db, and finally one more time to get C. Take each result and subtract the original scale length to get the distance behind the nut.

So, as above, (42 X 1.0594631 X 1.0594631) - 42 does indeed equal 5.14 inches behind the nut for low D.

[mikeem]

Originally Posted by robobass

There was an something long ago called the "ManCee extension" or something similiar. There was a cam in the pegbox under the E with a lever that dropped it to C, and there were also cams under the other strings which were operated by a second lever, allowing compensation for the change in tension, keeping the upper strings in tune. Also, at least in the picture it looked pretty lightweight and low key. Seemed like a great idea, but I never actually saw one. Someone out there must know something about it.

robobass
My father, John Mancini, invented the MANcEE device. I was curious if it was referenced anywhere on the web and, to my pleasant surprise, a google search led me here. The MANcEE never really caught on as he had hoped for several reasons, one being he became seriously ill soon after retirement and wasnt able to market and install the device anymore. Back in the early 1990s I tried to re-introduce a modified (refined?) version of it and sold several as a mail order kit but realized I was in way over my head and abandoned the idea.
I still have many of them. If anybody reading this needs spare parts, please send me a message and I will try to accomodate you.
Mike Mancini