Intonation - bridge placement/string height

[bssist]

Hello,

I recently pulled my old db out of the closet and started playing it again. After searching the forum for a day or so there are answers I have not found yet. Forgive me if I am too quick to post the questions before thoroughly reading all the pertinent posts.

I have found the specifics of where the bridge is placed. What I have not seen are the audio-physics (like that? I just made it up to diferentiate from the physics of the instrument such as sound post, bass bar, etc) of why it goes specifically in that spot.

If memory serves me correctly, when learning to set up my bass guitars, the placement of the bridge saddles was relative to string height and diameter. I would hit the 1/2 length harmonic, then hold that spot against the board (or fret on some instruments). I would then adjust the saddle to cause the harmonic to match the frequency of the 1/2 string length when pressed against the board (or fret).

Did I learn something wrong originally? Why is it that the bridge is not adjusted with string height and/or gauge on db?

Thanks for the insight.

Steve

[zeytoun]

1/2 string length by definition is where the octave harmonic is, no matter where you place the bridge.

Whether that's a millimeter one way or the other on the fretboard of a bass guitar is critical, with frets and all. But irrelevant on a double bass. Plus, it's kind of difficult to make tiny adjustments with individual strings, when you're dealing with a non-adjustable bridge.

[Cody Sisk]

Originally Posted by zeytoun

1/2 string length by definition is where the octave harmonic is, no matter where you place the bridge.

Whether that's a millimeter one way or the other on the fretboard of a bass guitar is critical, with frets and all. But irrelevant on a double bass. Plus, it's kind of difficult to make tiny adjustments with individual strings, when you're dealing with a non-adjustable bridge.

Agreed. String lengths vary quite a bit in double basses. Some people go so far as to adjust the position of the bridge and soundpost to affect the string length. This modification is usually requested by people using an alternate tuning (not in fourths) or have some physical handicap that needs to be worked around.

[bejoyous]

Originally Posted by bssist

If memory serves me correctly, when learning to set up my bass guitars, the placement of the bridge saddles was relative to string height and diameter. I would hit the 1/2 length harmonic, then hold that spot against the board (or fret on some instruments). I would then adjust the saddle to cause the harmonic to match the frequency of the 1/2 string length when pressed against the board (or fret).

You are thinking if the bass had frets. When there are frets and the bridge is in the wrong placement, then any note above the nut is slightly out of tune.

On DB, because there are no frets, you can adjust the intonation with your fingers to match other instruments/singers.

Anyway, the proper placements of the bridge is the side center of the feet should line up with the inside notches of the F-holes as in this video from Palatino Bass.

Then make sure the bridge is properly upright and making full contact with the belly of the instrument to maximize vibration transfer as in this video from Upton Bass.

When doing all this, it is easier if the bass is at a height and not on the floor, that way you won't accidentally fall on your instrument! If you are using a bench or kitchen table, stuff some books or other stuff around the edges of the bass so it is stable and the soundpost won't fall down.

Also, if the bridge is already set up and just in the wrong place by a little bit, you might want to carefully knock it around into place using the spine of a softcover novel.

[bigolbassguy]

Originally Posted by bssist

Hello,

I recently pulled my old db out of the closet and started playing it again. After searching the forum for a day or so there are answers I have not found yet. Forgive me if I am too quick to post the questions before thoroughly reading all the pertinent posts.

I have found the specifics of where the bridge is placed. What I have not seen are the audio-physics (like that? I just made it up to diferentiate from the physics of the instrument such as sound post, bass bar, etc) of why it goes specifically in that spot.

If memory serves me correctly, when learning to set up my bass guitars, the placement of the bridge saddles was relative to string height and diameter. I would hit the 1/2 length harmonic, then hold that spot against the board (or fret on some instruments). I would then adjust the saddle to cause the harmonic to match the frequency of the 1/2 string length when pressed against the board (or fret).

Did I learn something wrong originally? Why is it that the bridge is not adjusted with string height and/or gauge on db?

Thanks for the insight.

Steve

The bridge foot on the E string side of the bridge is supposed to rest directly over the bass bar. The inside nicks on the ff holes are aligned in optimum position - theoretically - in relation to the bass bar to transfer vibrations into the top plate. If the bridge is moved, the bass bar won't be working exactly the way it should.

[Cody Sisk]

Originally Posted by bigolbassguy

The bridge foot on the E string side of the bridge is supposed to rest directly over the bass bar. The inside nicks on the ff holes are aligned in optimum position - theoretically - in relation to the bass bar to transfer vibrations into the top plate. If the bridge is moved, the bass bar won't be working exactly the way it should.

This is very true but sometimes sacrificing optimal tone for another goal, playability, is sometimes a request I receive.