Different string lenght for each string?

No. This should not be. Are you sure the bridge is straight, or at least sitting how it was installed? A properly installed bridge should create equal string lengths. Making corrections at the nut seems quite dodgy.

 

Sorry, this is not correct. Due to the construction of bowed stringed instruments with more than two strings, there is always a difference between string lengths on the same instrument.
It is normal if it is only a few millimeters (on my 105 cm 5-string from the outer to the inner string the difference is 5 millimeters, but this is rather extreme).
A difference is normal, because of the bridge curvature and the string angle at the bridge. You only get no difference when the angle on the bridge is zero (or close to zero) or your bridge top "curvature" is flat.
But 5 mm from G to D is a bit much, I think (in my case it was from high C to D, so two string. I wouldn't expect more than 3mm between two strings, rather less.
Measure the string length on all your strings. If E and G don't have (approximately) the same length, then your bridge might not sit correctly. Have a look at the position of your bridge!

On a normal 4-string bass the difference is usually less, because you don't have a string running through the middle of the bridge.
The string angle over the bridge also can differ a bit for basses made for jazz or classical, I was told by my luthier.

The difference also depends on the bridge curvature. I have a rather high one to get a maximum bowing angle for each of the five strings (on my EUB with a highly curved fingerboard for bowing angles of a 4-string on a 5-string), so with less curvature the difference might be lower from outer string to inner string.

That's true.
If you would make corrections at the nut, the note positions are different on each string, and I'm sure a player won't like to compensate for that when playing.

 

I've also often thought (and I could be wrong) that another reason would be that they make the E-string (particularly) shorter so that you avoid putting wrapped string on the machine, since the E-string machine is closer to the nut.

But it is normal for strings to vary; on sets I have here, for instance:

Corelli E and G strings have a speaking length 2 inches shorter than the A and D
D'Addario Helicores, E is 1.5", and G is 1/2" shorter
Innovation E string is 1 inch shorter

I could go on, but you get the idea...

 

I think a difference of 5mm, or even 3mm, is unacceptable. I never measured the Pöllmann 5-string that I played on for many years, but I'd make a bet that there was not more than 1mm difference on this expertly set up bass. Equal string length is something that a proper luthier takes into account when carving a bridge. If there are factors which interfere with this goal, then the customer should be notified. My opinion, anyway. It's hard enough to play in tune even if the strings are all the same length. I am not a luthier. Pros, please chime in!

 

It was not easy to understood in the first place what Andrea meant, but it was vibrating string length, not total string length.

I measured the EUB vibrating string lengths again: E-A: +2mm, A-D: +1.5mm, D-G: -1.5mm, G-highC: -2mm.
So I mismeasured by 2 mm the first time and my bridge sits a little bit closer to the nut on one side.

On a four string I would expext about 1 to 2 mm length difference, closer to 1 mm from outer to inner string.

It's a matter of physics/mathematics that the string length differ. You can reduce the difference but only on other cost as less to none bowing angle or smaller string angle at the bridge (which means less pressure on the top).
Of course, you could screw the bridge to the top (as on my EUB originally) to have it perpendicular to the vibrating length of the strings without the risk of a fallen bridge. But this is really bad and the first thing I corrected on my EUB.

 

I just checked my Pfretzchner 4 string. The A is indeed 2mm longer than the G or E. Many bridge tops are curved to compensate for this. I don't mean the curve to match the fingerboard radius, but a second curve seen when looking straight down, perpendicular to the top. My luthier here carves a curve into the fingerboard side to increase the speaking length of the outer strings. I've also seen bridges where some of the string slots were made thinner individually to deal with the equal length issue. I guess I need a new bridge! Anyway, I think a difference of 2mm won't affect much. I'm quite used the the bass, having had it for eighteen years. Also, in the neck positions the difference translates down to almost nothing. 0.25mm between strings at the first C on the G string. That's less than a hundredth of an inch. Can any physics nerds out there convert that into hundredths of a semitone? 5mm does however, seem like too much.

 

Yes, I misunderstood. So note that my measurements are for "un-strung strings" - the speaking length portions of the strings vary from position to position. Once on the bass, you'd think they'd be very very close in length.

 

One more idea on this...
On slabs we can individually adjust each string at the bridge to "set the intonation". Generally this means matching the octave harmonic to the closed note at the twelfth fret. IME, this sometimes produces surprising "speaking" string-length settings. On unfretted double basses, I don't know if anyone really checks to see if the fingered octaves (or harmonics for that matter) are actually perfectly orthogonal. So, based on that, it seems that you cannot expect a perfectly lateral move to the next string to produce a perfect fourth, even if the strings are all exactly the same length!

 

robobass,
Yes, on my 5 string "slab", the low B string is set at 34 9/16'' (for a "34 inch scale), and the lower position notes on the B string play in tune. Even the G string is not a the "theoretical" 34", ( it is at 34 1/16"). Placing the bridge during the build was critical, as the Gotoh bridge allows for about 1/2" of difference in speaking lengths between the G and B strings. ( I missed on the first try...).

I've always thought that as the gauge (diameter ) of the string increases, the stiffer the string is at the point where it crosses the Bridge or saddle and at the Nut, which necessitates a longer "speaking" string length, as you mentioned.

I wonder if anyone has thought of fabricating/machining a doublebass bridge with normal feet, but with a "twist" in the top half or some other way to compensate for the lower strings increasing stiffness and required increase in speaking length?

( Also too - I appreciated your previous responses in the thread re: tuning a C-extension, as well. Thanks).
Thanks for your time and interest.

 

A twist would be bad for the transport of the force from string to top.

But you can move the bass leg more towards the tailpiece. Not the optimum solution but usable. Anyway, when do you play up the fingerboard on the E-string?

The thing is more complicated if you want all notes in tune. It even depends on the string you use, so there is no universal optimal solution for that. Also the nut (and frets for a bass guitar) should be corrected then. Nobody would pay for such a lot of work nobody really hears because of audible feedback correction (on a fretless fingerboard).

 

Any moreso than moving one leg? I agree that it's not a good idea to do either.

 

With all due respect, if it's never been done before, I would argue that fabricating a compensated/"slanted" doublebass bridge, (with about 3/8 inch length added at the E string side), and "normal" foot placement, would be a great idea.

Just thinking outloud: you'd need a bridge blank of about 2x the thickness of a normal bridge blank to accommodate the "slant" from the G side to the E side, ( while maintaining "normal" feet), and a Bridgeport vertical milling machine...
So many ideas... So little time.

Thanks for your time and interest.

 

Seems like a complicated solution to a problem that doesn't really exist. Likely why it has not been done before, at least on any grand scale.

 

+1,000 I'm amazed this thread is still going.