About Acoustic Feedback - Fishman LOUDBOX ARTIST User Manual

About Acoustic Feedback

Feedback usually occurs in the lowest octave of your instrument, generally with
two notes about a half step apart. The lower type of feedback (cavity resonance)
starts when the sound pressure coming out of the speakers excites the resonant
air chamber inside your instrument. We have found that it is effective to tune out
an instrument's cavity resonance feedback with the Anti-Feedback (notch fi lter)
in the Loudbox Artist. For acoustic guitar this occurs at G# on the low E-string, or
at about 100Hz. Turn the Anti-Feedback knob to about 11 o'clock to dial out this
resonance. Note that the circuit can be effectively defeated by moving the dial
to the Off (7 o'clock) position.
The higher range of feedback (top resonance) usually starts about a half or whole
step above cavity resonance of the instrument. Top resonance feedback
happens when the sound pressure coming off the speakers excites the resonant
frequency of the soundboard of your instrument. For acoustic guitar, this occurs
at A and above on the low E-string. Push the Phase switch in and out until you
fi nd the position that subdues top resonance feedback.
Feedback
Lower
Feedback Range
(E to G#)
Upper
Feedback Range
(A and above)
Anti
Phase
9