Double Bass Bass bar sinkage

[landoband]

Hi All, first time poster here. Hoping for some guidance as a trip to the luthier is not possible right now.. The bass is a romanian flatback, about 10 years old.

5 days ago my bass started to buzz on almost every note pizz. Lightly touching the sound post stopped the buzz. I couldn't find any open seams and it wasn't a pickup, string winding or vibrating endpin issue. I finished practicing and put it in the corner.

Three days ago I was playing again and there was a quieter buzz on certain notes (mostly Ab). Again I started touching around the bass to find the buzz and this time I noticed that there was a bit of sinking on the top, next to the bass bar. Not drastic but noticeable. When I lay the bass flat on my bed and look from the saddle, I can see the difference in the arching. It's mostly below the bottom of the f hole.

I've felt around that area recently and never noticed any sinking, is it possible this kind of change could happen quickly, like the course a week? The bass had Spiro Wiechs on it with a Chorda gut G for about a 6 months. Two months ago I put on a Mittel G and E.

The buzzes are now intermittent and quiet. Touching around the bass bar area doesn't stop the buzz. I do get a slight *clack* sound when I tap the spot marked with painters tape in the photo. I tried to get some photos of the bass bar with my phone. Is it possible to tell anything from these?

I tuned the strings down about 2 tones and put it in the corner as a precaution. It's my only bass right now hoping I can keep playing it but don't want to risk any more damage if it's something that needs to be addressed soon.

Thanks all,
Lando

 

[KUNGfuSHERIFF]

How did you check the seams? I rap on the edges with a knuckle and listen for any changes in sound.

How do you heat your living space?

How do you humidify and to what degree?

Odds are it’s a seam, and a back brace might also be loose. I didn’t see anything concerning in your photos.

 

[Eric Hochberg]

Could be a rib crack, too.

 

[landoband]

Glad to hear neither of you are concerned about the bass bar.

I went around the edge tapping and listening, and then got up close to check visually. I'll check again. I'll check the ribs specifically too.

Heating is central air - furnace.

I have a wick humidifier that's in the same room as the bass. I don't have a standalone humidistat so I leave the built in one set at what should be 40% humidity although I'm sure it's not terribly accurate..

 

[unbrokenchain]

You can also put your christmas lights back in the bass and turn out the lights in the room, sometimes you can see light coming through an open seam.

 

[james condino]

Seasonal soundpost buzzzzzzz??? I used to have a bass that no matter how much I worked on it, that one always came up- twice a year. It is springtime in Ontario, after a cold winter no???

 

[KUNGfuSHERIFF]

Heating is central air - furnace.

I have a wick humidifier that's in the same room as the bass. I don't have a standalone humidistat so I leave the built in one set at what should be 40% humidity although I'm sure it's not terribly accurate..

I see your problem.

 

[landoband]

Need more consistent humidity?

 

[landoband]

Seasonal soundpost buzzzzzzz??? I used to have a bass that no matter how much I worked on it, that one always came up- twice a year. It is springtime in Ontario, after a cold winter no???

Not an especially cold winter but it is definitely getting warmer now. I don't think I've ever had a problem with the sound post before.

What causes the sound post to buzz? With the strings tuned down heavily the post stays in place when the bass is standing up.

 

[David Potts]

Make sure that the feet of the bridge are fitting down on the belly. The bridge will tend to rock forward towards the fingerboard because of the unequal angles of the string bending over it. If you lower the tension is there is a clatter when you tap over the bass bar for its full length and beyond to above and below it. Did the clatter that you placed tape over disappear? Sometimes a bass bar may come loose somewhere else other than each end. If it is loose at the top or bottom I would expect more of a death rattle. Another source of rattle may be the end pin.

An open seam, especially around the lower bouts, is another source of clatter. A buzz suggests a much higher frequency of vibration. The loose end of a back brace or a loose centre seam patch inside the front or back would tend to buzz on a certain note. Another frustrating source of buzz is possibly loose purfling. One more source is a loose string winding between the bridge and tailpiece. And there is perhaps the top of the sound post not quite fitting. I suggest enlisting the aid of another person to press down all over the front and back while you produce the buzz to see what makes it stop.

IME the bottom Aflat is often the "dirtiest" note that becomes a wolf note when its octave is played on the A string. It can set up the sort of vibrations that find buzzes and clatters.

I hope all this helps. Good luck and stay safe. DP