Double Bass Tuning instability : possible structure problem?

[luisraulmunoz]

If the neck was unstable in a way that affected the tuning, you should be feeling a clear difference in action/string height also.

Actually I didnt feel a notable difference in action/string height.

 

[luisraulmunoz]

My (limited) understanding is that the whole instrument swells with humidity, which slightly increases the distance between top and back plates. If the post was cut in a much different environment, there might be more top movement in the humid environment than ideal. Again I'm absolutely not a luthier but it's one hypothesis.

Might also check the fingerboard glue joint as Ben Green suggested, and you'd probably be having other big issues if the bass bar was loose, but might as well look in there with a flashlight and mirror and rule it out?

I checked and fingerboard and bassbar seem fine.

If I think about every bass over the years that I have brought to Puerto Rico from the US or Europe, there has always been a period of one or two days even of the instrument adapting to the tropical humidity. In all cases the string height raised considerably sometimes making it necessary to lower the bridge. It really is amazing how different the tropical climate is in that regard.

 

[luisraulmunoz]

Wow, thanks to everyone for the helpful insights. After considering all the comments I feel the problem is probably too short soundpost plus bad tuning gears plus the fact that no matter what there is always some adjustment period when going a non air conditioned place to a hall with air conditioning, the thing being that the soundpost being short and the tuning gears exacerbated the problem. So I was being probably paranoid about the neck after all.

 

[David Potts]

One last thing to check? See how the strings each pass from their peg to the nut in the peg box. The method used to secure the strings when they are changed and the care taken to align and wind them up neatly from slack to playing tension are important. Also the pegs may not be aligned nicely, causing the D or A strings to bend over them. If string windings are lumpy/untidy and a string bends over them you might find that as you tighten or loosen one string you also change the pitch of another. Just a thought.

 

[notabene]

Looking at the first pictures, it seems the neck may have shifted (triangular shadows at the joint, both sides). My bass recently fell off the chair it was resting on, at a gig, and, though it still played, was no longer stable in tuning. I soon realized the neck, though still attached, and unable to be felt moving, was in need of resetting. I reset it (hidden dowels from a previous hack job made it difficult), and now it sounds better than before its accident. Here are some pictures of mine.

 

[KUNGfuSHERIFF]

Folks, PLEASE, no dowels. You’re actually removing material and making a weaker joint.

 

[luisraulmunoz]

View attachment 3420582 Looking at the first pictures, it seems the neck may have shifted (triangular shadows at the joint, both sides). My bass recently fell off the chair it was resting on, at a gig, and, though it still played, was no longer stable in tuning. I soon realized the neck, though still attached, and unable to be felt moving, was in need of resetting. I reset it (hidden dowels from a previous hack job made it difficult), and now it sounds better than before its accident. Here are some pictures of mine.View attachment 3420582 View attachment 3420582

Well this bass hasn't been in an accident since I own it. The instability occurs when changing temperature (different venues). When I'm at home it's pretty stable, exception when it rains (humidity increases) strings will go up in tune and a bit in height, but that has been the case with every bass I have used in Puerto Rico.

I'm trying to find the triangular shadows you speak of.

 

[notabene]

Luis,

Your first two pictures: 1st picture, triangle shape from bass top side (left)-thin apex crescendo shape to back (right) where the neck joins the body. Perhaps a quarter inch wider at back. Identical on picture two. If this is not an illusion in the photo, it may indicate that the neck has at some time, moved, within the block, raising the action. If it happened a long time ago, it could still indicate possible subtle motion is possible.

Steven

 

[notabene]

Folks, PLEASE, no dowels. You’re actually removing material and making a weaker joint.

I cursed the idiot who did this when I discovered it.

Steven

 

[CreativeBass]

Having lived in a high-humidity environment for almost 20 years, I can relate to your concerns. The fluctuations can be extreme and will always effect the bass, sometimes very quickly.

Your bass neck looks fine and the fingerboard is definitely thick enough to give stability. I don't think the tuners are the culprit ... unless you can clearly determine slippage. (I also do double bass repairs and restorations, so I am familiar with many circumstances.)

As already suggested elsewhere, I would replace the tailpiece wire with braided stainless steel, 2mm diameter. Do that first.

What strings are you using?

Your bass is beautiful. Do you know any of its history?

Here is a link to Invalid Link Removed. There is a photo of a gut tailpiece "wire" on a bass I repaired. In this case the gut works well because the strings are gut and don't have the tension of steel strings.

I would like to see the height of the tailpiece from the lower nut. Can you post a photo of that?

Thanks and kind regards from Down Under Australia.

 

[CreativeBass]

Luis,

Your first two pictures: 1st picture, triangle shape from bass top side (left)-thin apex crescendo shape to back (right) where the neck joins the body. Perhaps a quarter inch wider at back. Identical on picture two. If this is not an illusion in the photo, it may indicate that the neck has at some time, moved, within the block, raising the action. If it happened a long time ago, it could still indicate possible subtle motion is possible.

Steven

Yes, I noticed this, too, and have had exactly the same issue in high-humidity environment. Since then, I always store the bass in its bag when not in use.

It looks like the neck may have moved and that the heel button was filed down. You can check current movement by holding the bass body and pulling on the neck. If there is movement, then the neck needs a re-set. Also, check if there is a slight gap between the button and the neck heel. If you can slide a razor blade in there, then it needs a re-glue.

 

[luisraulmunoz]

Yes, I noticed this, too, and have had exactly the same issue in high-humidity environment. Since then, I always store the bass in its bag when not in use.

It looks like the neck may have moved and that the heel button was filed down. You can check current movement by holding the bass body and pulling on the neck. If there is movement, then the neck needs a re-set. Also, check if there is a slight gap between the button and the neck heel. If you can slide a razor blade in there, then it needs a re-glue.

Hi, thanks for the insight.

You are correct @CreativeBass , as @notabene mentioned, the neck had shifted a little. Considering that the fingerboard had been ruined by a luthier some years ago and other problems and the fact that I didnt have the cash, time and certainty I could fix everything at this moment I opted to trade it in for a new instrument which is more ergonomically sound for me (that bass was always awkward, not large but heavy and difficult to feel at ease with even if it had a very nice sound)
The bass had an origin attributed to "Prague" circa early 20th century and had very pretty and nice wood.

Not sure if the neck was still moving but by far it is the most sensitive bass to humidity I ever owned here so if there was loosenes, which I was able to confirm later, that seems to have been the major cause of the problem. Unfortunately here in Puerto Rico there is no one that can do proper neck resetting or major fingerboard work at the moment and I didnt want to do the "experiment" since I dont have the time and money to invest.

But thanks to everyone for the comments and discussion, I learned many things.

 

[CreativeBass]

Hi, thanks for the insight.

You are correct @CreativeBass , as @notabene mentioned, the neck had shifted a little. Considering that the fingerboard had been ruined by a luthier some years ago and other problems and the fact that I didnt have the cash, time and certainty I could fix everything at this moment I opted to trade it in for a new instrument which is more ergonomically sound for me (that bass was always awkward, not large but heavy and difficult to feel at ease with even if it had a very nice sound)
The bass had an origin attributed to "Prague" circa early 20th century and had very pretty and nice wood.

Not sure if the neck was still moving but by far it is the most sensitive bass to humidity I ever owned here so if there was loosenes, which I was able to confirm later, that seems to have been the major cause of the problem. Unfortunately here in Puerto Rico there is no one that can do proper neck resetting or major fingerboard work at the moment and I didnt want to do the "experiment" since I dont have the time and money to invest.

But thanks to everyone for the comments and discussion, I learned many things.

I am happy to see you found a solution that is satisfactory to you. Yes, if an instrument does not feel right, then it is time to move on. Bass neck re-setting is quite a delicate job that need lots of attention and accuracy. I have done a few re-sets. Thankfully all of them have been very successful.

FYI: If the neck join is loose once (and not been re-glued) then you will always get "ups-and-downs", i.e. humidity-related movement or stability (depending on the humidity at the time).

Anyway, All the Bass! We are always learning