Double Bass Afterlength coupling

[drurb]

Last week, I had a rather involved discussion with a friend who publishes on violin acoustics. He mentioned that some instruments seem to benefit from coupling vibrations across strings in the afterlengths. It didn't make any sense to me at all but he challenged me to give it a try. He suggested that, on a bass, it could be easily accomplished by opening up a large paperclip and clamping one end to the afterlength of the A and the other to the afterlength of the D. The idea is that you're creating a mechanical coupling across the two "tuned" afterlengths. Figuring I didn't have anything to lose, I gave it a try. Wow! What I heard was a substantial increase in the sustain of notes in the upper register. A fluke? I managed to convince a bass-buddy to give it a try. Same effect.

I'll put this in the category of other things I don't understand, such as the changes many hear when swapping tuning pegs. The difference here is that there is, apparently, some known physics behind it. I aim to understand how it works.

Give it a try! It just takes a minute or two.

 

[Jake deVilliers]

And this after pooh-poohing my advocacy of after-length tuning for all these years?!

Glad you woke up, Doc!

 

[Eric Hochberg]

Can't really hear a difference here.

 

[drurb]

And this after pooh-poohing my advocacy of after-length tuning for all these years?!

Glad you woke up, Doc!

Not me, Jake. I never poo-poohed afterlength tuning at the tailpiece. In fairness to you, I did say that I could not understand the basis for changing the afterlength in the pegbox. That's still true. I don't understand it. I would never deny your experience. If I ever came close to doing that, then I was wrong to do so. It's the explanation that didn't seem to make sense.

I'm an empiricist, anyway. I'm never against giving it a try if there is little to lose. I would like to hear what you find by coupling the afterlengths.

 

[Michael Case]

Wouldn't mounting a pick up jack on the after-length do same thing?

I also have a feeling this may have to do with the date April 1st!

 

[Eric Hochberg]

Got me, Drurb!

 

[powerbass]

how did you clamp the paper clip and did you try all the strings or just A & D?

 

[ctxbass]

Got me, Drurb!

Me too, and I made the thirty mile trip into town to buy paperclips.

 

[Mark Gollihur]

He had me until he said,

"I'll put this in the category of other things I don't understand..."

There's the giveaway, because I've never known drurb to admit he didn't understand anything.

(He said, with a playful punch to the arm...)

 

[drurb]

He had me until he said,

"I'll put this in the category of other things I don't understand..."

There's the giveaway, because I've never known drurb to admit he didn't understand anything.

(He said, with a playful punch to the arm...)

I'm still wondering about that tuner-swapping effect. Everyone can rest assured that one thing I do understand is that there are far more things I don't understand than those I do. The fun of my day job is trying to unravel some of the mysteries that are closest to my heart.

Speaking of understanding... it's often a matter of degree. Walk into a gas station and ask the mechanic how a car battery works. He'll tell you. Ask a physicist. He'll tell you he has no idea.

Thanks to all of you for your good humor! Eric, I owe you a paperclip.

 

[nicechuck]

Do you think it's the bit of added tension? I should try putting my pickup jack on the E and A string

 

[DoubleMIDI]

There is no added tension if your afterlengths or peg box string lengths are longer. THe tension of the string is the same over the whole length of the string.

I wouldn't put the pickup jack on the E and A, because these strings are much stiffer than the higher ones and hey need more length for better vibration than the higher ones. Better mount the jack on D and G.

 

[Vic Koler]

Great post! You really cracked me up.

 

[61pollmann]

I've read many posts and articles about how the afterlength pitch should be a pitch related to the open string tuning. Wouldn't this relationship become something totally different once you are playing something other than the open string? For instance, if the G string afterlength was tuned to a D(part of the harmonic series of overtones), what happens when you finger an A-flat? The afterlength pitch is no longer part of the overtone series. I was invoved with a similar discussion regarding pickup placement on a bass guitar. As you play on higher and higher frets, the pickup is in a different location relative to the vibrating length of the string.

Just wondering?

 

[powerbass]

on a more serious note....I have a wolf tone eliminator attached to the D string after length to dampen a nasty Ab wolf tone on my Thompson RM200. Yesterday I decided to take it off and see what my bass sounded like. there was a distinct increase in volume and clarity and interestingly the wolf tone was gone. so maybe paper clips in the after length might actually be a good rhing

 

[drurb]

on a more serious note....I have a wolf tone eliminator attached to the D string after length to dampen a nasty Ab wolf tone on my Thompson RM200. Yesterday I decided to take it off and see what my bass sounded like. there was a distinct increase in volume and clarity and interestingly the wolf tone was gone. so maybe paper clips in the after length might actually be a good rhing

Yes, and copper paperclips would be more likely to cure wolf tones so that they can be removed later. Same idea as copper bracelets.

Really though, I suspect that other setup-related aspects of your bass changed so that the wolf tone vanished.

 

[61pollmann]

Still hoping for any comments on my previous post.

 

[Jake deVilliers]

I've read many posts and articles about how the afterlength pitch should be a pitch related to the open string tuning. Wouldn't this relationship become something totally different once you are playing something other than the open string? For instance, if the G string afterlength was tuned to a D(part of the harmonic series of overtones), what happens when you finger an A-flat? The afterlength pitch is no longer part of the overtone series. I was invoved with a similar discussion regarding pickup placement on a bass guitar. As you play on higher and higher frets, the pickup is in a different location relative to the vibrating length of the string.

Just wondering?

The after-length pitches need to be related to the pitches that you are using in the instrument - its just easy to say "The after-lengths work best if they are two octaves and a fourth higher than the open string."

If the after-lengths are close to pitch but not quite, there's a phase cancellation effect that 'thins' out the partials in the region of that note.

If, for instance, the D string after-length is at 385 Hertz instead of G 392 Hz, that vibrating element will have a deleterious cancelling effect on any 392 Hertz vibrations that try to exist in the instrument, whether they be fundamentals or partials - the notes will sound neither fat nor full.

Read these to start with:

http://www.music.vt.edu/musicdictionary/texto/overtone.html

http://www.freefictionbooks.org/books/g/9218-general-science-by-bertha-m-clark?start=125

http://en.wikipedia.org/wiki/Overtone

http://en.wikipedia.org/wiki/Overtones_tuning

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