Hi all, I've just finished a 4 string acoustic bass. I'm getting a warble/whistle when I play particular notes, which at times is very clear, then at other times disappears almost completely. I'm hoping you can help me establish what the cause is, and whether I can do anything about it. Here's a link to the recording (for some reason OLF wouldn't let m upload either m4a or mp3 files....)
https://drive.google.com/file/d/1BO2EIT ... drive_link
The bass is very responsive. The Monopole Mobility is 21 which seems very high, though interesting the bridge rotation is only 1.4 degrees even with D'Addario Chrome flatwounds which are pretty high tension.
The Air, Top and Back resonant frequencies are as follows:
82, 164, 226
I note a couple of things. The Air resonance is exactly half the top resonance. The Back resonance is somewhere between A and Bb, which is where the warble tends to occur.
Strangely, the warble seems to come and go. Sometimes it will have disappeared almost completely, other times it's very clear, like in the recording above.
I have tried blocking off the sound hole, to see if the 82/164 is the problem. The resonant frequencies were as follows:
- , 155, 214
But the warble was still there.
I've also tried adding 19g of putty to the bridge (soundhole uncovered). Again the resonances moved, as follows:
82, 155, 226
But the warble was still there. Or was sometimes still there, then would disappear.
The guitar is newly built, so obviously I'm hoping it's not a loose brace, or badly glued bridge. There's nothing obviously rattling when I shake it!
Does anyone have any thought about how to establish where the problem lies, and what to do about it? If anything. Acoustic basses are obviously super sensitive to wolf notes and mis-matched resonant frequencies. That's how I build them, so I've only got myself to blame
Edit: I should say I've already checked that the saddle and nut are flat-bottomed, and changed the strings.
