Responsiveness in Acoustic Guitars.


Portland Guitar claims that curved bracing(falcate) is more responsive than traditional X-bracing, a Collings D2H and a Portland Guitar are compared to show this. We record the difference in theoretical and recorded note at each string of each fret(intonation errors). Near the air resonance of the body (f#-A#) an interaction occurs. This interaction is the response of the guitar to the natural low frequencies.  

These graphs show the difference between desired and received note in guitars with different bracing patterns. First is a Collings D2H 

Un-responsive collings d2h guitar

This uses a traditional x-bracing system. You can see that each note runs a little sharp. Around the air resonance, F# to A2, there is constructive interference occurring causing a peak. There is little to no frequency shifting as the air resonance is overpowering the string.

 

Here is a Portland Guitar with a falcate bracing pattern.

Responsive guitar with low intonation errors

Between F# and A# the frequency is shifted dramatically sharp and dramatically flat. The top and back are very well coupled together through the air cavity.

The guitar with falcate bracing exhibited a frequency shift around the air resonance of the cavity. This only occurs for coupled oscillators in which one responds to the other. This is the definition of responsiveness: how well coupled the string and air resonance are.