Double Bass Lowering only the D string height at the bridge

[Chris Fitzgerald]

A student with a new bass cannot afford a trip to the luthier both in terms of time and $$$ at the moment. The setup of bass is OK, but typical of an orchestral setup, the D string is too high in comparison with the other strings. Is there a simple and safe way for a person like me to help them lower the D string by about 1mm to tide them over until the thing can be done properly by a luthier? If so, what specific tools would be needed?

 

[Povl Carstensen]

I use a round metal file

 

[Eric Hochberg]

I've done this for myself using a round rat-tail file. Go slow. I take a swipe or two with the file and then try it out until I get the desired height. Try not to widen the slot more than it is. Make sure to keep the slot rounded so the string doesn't bind and use graphite to lube.

 

[Reiska]

Small enough file will do. Go slow, check that the bridge sits straight with a ruler against the center of back of the bridge ( it can be out of line to begin with and move more once you start filing ) and measure the string height at all stages, before starting, while on it and stop when you`re close to the height you`re trying to achieve. You can mark the desired height to both sides of the bridge with a pencil before filing for rough reference. Patience is your best friend and if you get tired while you`re at it take a break.

 

[robobass]

You don't even need to spend $$$ for the files. A Chinese needle file set from Harbor freight will work fine. Just make sure they are traditional files and not the diamond coated ones.

On Ebay you can get this for 4 bucks:
10pc PRECISION NEEDLE FILE RASP BASTARD SET NEW!!! | eBay

Or this for $160:
Needle File Set,Swiss,6 1/4 In. L NICHOLSON 37761 | eBay

I've never tried those Nicholsons. I bet they are a dream!

 

[Don Hergert]

In a typical Needle File Set (NFI) you will find a small, completely round profile (rat-tail) hasp. Needle files are pretty fine as far as precision is concerned, and they do a good job on bass bridges, nuts and other instrument related jobs. I've found them one of the essential tool kits for instrument maintenance through the years.

A good option is to practice on a similar piece of scrap wood before you start work on the the real thing.

As Reiska suggested, go slow, use straight strokes as much as possible, taking a little bit of wood with each stroke. Take out less wood than you think you want to remove at first, then test it, then if necessary take out more.

Try to match the angle that the string enters and leaves the bridge with the same angle that the rest of the strings have.

 

[1st Bass]

Check the diameter of the string with a caliper...sometimes one can buy a very small-diameter chainsaw file in a saw-shop, made for small electric chainsaws...and they are very good, perfectly round, quite inexpensive files. The nice thing is that they are relatively long, and perfectly cylindrical. But there are limits as to how small saw-teeth can be, so, perhaps on the D-string it will not be available.

 

[damonsmith]

I need to get the A and E down a bit on my Chadwick, considering this...

 

[Chris Fitzgerald]

Great replies... thanks, everyone. On the bass in question, when the G is in the right ballpark the D is too high and the A and E are too low. I have seen some basses with string notches cut into the bridge that are way deeper than normal, as if the player had deepened them to adjust the height and just never sanded the crown down afterwards.

What are the drawbacks of this as an intermediate measure?

 

[Eric Hochberg]

Great replies... thanks, everyone. On the bass in question, when the G is in the right ballpark the D is too high and the A and E are too low. I have seen some basses with string notches cut into the bridge that are way deeper than normal, as if the player had deepened them to adjust the height and just never sanded the crown down afterwards.

What are the drawbacks of this as an intermediate measure?

The only drawback I can think of is the bridge widens out as you go lower so the string is sitting on more material. As long as the strings move smoothly all should be fine, at least temporarily.

Sounds like you need to raise the bridge so that the A and E are good, and then work on the D and G string. Hope it has adjusters.

 

[Chris Fitzgerald]

The only drawback I can think of is the bridge widens out as you go lower so the string is sitting on more material. As long as the strings move smoothly all should be fine, at least temporarily.

Sounds like you need to raise the bridge so that the A and E are good, and then work on the D and G string. Hope it has adjusters.

It does have adjusters. We are thinking along the same lines! I'm used to the "Starting at the G, each string goes up by 1mm" basic setup feel. This bridge isn't cut that way, and I'm looking for the easiest way to get it headed in that direction. I'm thinking "lower the G slightly, lower the D slightly more, and let the adjusters take care of the A and E". Then when it goes to a luthier, they can sand down the treble side of the bridge to make the notches the right depth.

 

[Don Hergert]

It'd be nice to hear from one of our highly talented luthiers here because we're getting into nuances where their advice might be very helpful...

Short of that, here's my player/maintenance-minded thinking about notch depth, related to sanding the top of the bridge down after adjusting the notch depth...

It really depends on what the bass is used for. For primarily arco, it's good if the strings only barely sit inside their notch, meaning that the bridge top has been sanded leaving the new notch very shallow. For serious pizz, or even more so with slap/pizz -- and especially if the strings are low tension -- the strings have to sit fairly deeply in their notch or they'll slip out with playing, meaning that the notch has to be relatively deep. That said, a deeper notch should also not be so narrow that it entraps the string, deadening it.

And lastly, deepening notches and sanding the bridge top down does have the potential to change the tone because the string tension may be lower, and because the vibrating/transmitting mass of the bridge is reduced. The same goes for sanding the feet of a bridge to improve fit on the top. So this work needs to be done sparingly.

Given all that and given that the human ear -- and the mind behind it -- is very subjective, it's best to always assume that any change changes tone.

Luthiers, because they do this work all the time on a variety of bridges and basses, have a sense for what is right related to keeping the strings in place while playing and related to the tone quality.

 

[Greg Clinkingbeard]

Don’t overthink it. Get a small rat tail file and go to it. Be sure to file it just barely wider than the string and drop the file on either side of the bridge so the slot follows the angle of the string as it sits on the bridge. You want the string to contact the exact front of the bridge, but not have a sharp edge there.
Hit it with a #2 pencil for lubrication.
If you’re only lowering it 1-2mm I wouldn’t worry about the depth or adjusting the top of the bridge.

 

[Jon Stefaniak]

You could also take some scrap length of string slightly thinner than his D string (A bit of electric bass string) and wrap it in sand paper. Maybe 240, or 320... If you have it , maybe finish with 600. It won't take much to get it right, so the hard work is definitely in detuning and tuning back up to check.

 

[KUNGfuSHERIFF]

Chainsaw file. When the height is right, put a drop of superglue in the slot and sprinkle a little graphite dust in the glue before it sets.

I wouldn’t worry about re-crowning the bridge. We’re talking about a single millimeter here.

 

[David Potts]

The tensioned bow hair makes a very good straight edge to compare clearances when rested on the D and A strings. I have always made the grooves 1/2 the thickness of each strings. My observation is that deep grooves don't work as well. So long as you leave two strings up to tension you can sand down the top of the bridge after adjusting the string height while keeping in mind the broad curve of the top. I totally agree with round the grooves and using soft lead pencil to lubricate them. It is also a good time to use the pencil and/or rat-tail file in the nut grooves. I lower the grooves until I can just slide a business card up to the nut under each string.

 

[DoubleMIDI]

Reshaping the bridge crown with a file is no major thing. But first check that the deepened notches work as expected before reshaping the crown. Start on top with the curvature and round the edges later.
And the reshaping would be easier with the bridge removed from the bass. Laying the bass down on a bed or carpet before slackening the strings might hold the sound post in place (at least on my bass when I did this).

Just use the file from the middle of the crown towards the sides, never in the opposite direction because of the wood grain.

For deepening the slots do this perpendicular to the top, not perpendicular to the bridge crown tangent, because the later would move the string on the fingerboard a bit sideways.

 

[turf3]

I did this a couple years ago. I'm not sure, because I do own a set of needle files, but I think I just used the tip of a new sharp Xacto knife. I am sure I would have beveled the tailpiece side of the slot so the length of the contact area wasn't lengthened too much. A nice new sharp Xacto blade will also allow you to make a nice neat very small chamfer on the fingerboard end of the new slot.

I would certainly use a sharp pencil to blacken all of the existing slot so you can tell where you're cutting away; check frequently, and re-blacken with pencil multiple times so you can see clearly where you are removing material.

 

[KUNGfuSHERIFF]

My observation is that deep grooves don't work as well.

They do if you slap, especially the E. It’s...awkward.

 

[damonsmith]

Reshaping the bridge crown with a file is no major thing. But first check that the deepened notches work as expected before reshaping the crown. Start on top with the curvature and round the edges later.
And the reshaping would be easier with the bridge removed from the bass. Laying the bass down on a bed or carpet before slackening the strings might hold the sound post in place (at least on my bass when I did this).

Just use the file from the middle of the crown towards the sides, never in the opposite direction because of the wood grain.

For deepening the slots do this perpendicular to the top, not perpendicular to the bridge crown tangent, because the later would move the string on the fingerboard a bit sideways.

I got a set of Husky precision files at Home Depot and brought down the E and A, I did the same amount each and reshaped the crown. It was easy and the bass plays better. I sent my action to Charlie when I had it a bit higher, so it ended up that with the adjusters all the way down they were on the high side, obviously, I want them on the low side and I have been playing with a bit lower action. It was fun to have the action higher on the travel so I could come home to an easier time on the main bass, but, that also got old.