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Mystery of misbehaving F3 note.


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4 hours ago, ttonon said:

Lukasz, from my calculations, I see no possible resonance interference with the tongue vibration.  This applies to both Helmholtz and quarter-wave tube resonance.  

 

I thus cannot make a suggestion here, only I'm still not clear on what the basic problem is.  Are you saying that all the F3 reeds you put into the "bad" cavity show the same problem?  Also, that when you put those same reeds into a different cavity but with the same dimensions of the "bad" cavity, there is no problem?  

 

Best regards,

Tom


Exactly. Bad cavities are on the LH side of the instrument and good ones are on the RH, reeds are identical and it does not matter which one I mount where. The .wav file above is with endplates mounted, but this problem is present without the endplates as well. Endplates emphasise it further.
 

Some parameter of reedpan is causing this but not simply inner vs outer chamber placement, as both initial chambers are outer ones. I suspect it is either amount of solid wood block left in the reedpan, differences in reedpan’s wood parameters between sides or the exact layout of surrounding voids, because I can get significant improvement in spectrum shape during tests by using tack to mount the reed to the reedpan instead of rigid screw connection and thus decoupling it mechanically. 
 

But using tack is not a valid permanent solution so I’ve settled with increasing chamber depth to bring missing partial back as a way to rebelance this instrument. It is not ideal, as I loose some higher partials this way, but it sounds way smoother now.

 

Perhaps it is now easier for you to understand why I said, that reeds seem to not care too much for our simplistic mathematical models :D 

Edited by Łukasz Martynowicz
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