Fishman Blender User Manual download pdf (Page 10)

FISHMAN PREFIX™ ONBOARD BLENDER

Continued from Page 9

Here's why:

A typical guitar has a cavity resonance of about 100 Hz. This is the frequency

that generally feeds back when a mic'ed guitar and speaker are

in phase.

100 Hz has a wavelength of about 11 feet.

Phase inverts 180° for every 1/2 a frequency's wavelength. In this case, 1/2

the wavelength is about 5 1/2 feet.

If you set your PHASE switch to eliminate cavity resonance

(out of phase)

and

then move 5 1/2 feet towards or away from the speaker, you will effectively put

the mic'ed guitar/speaker relationship at 100 Hz back

in phase;

in the line of

fire for low frequency feedback.

B. USING THE NOTCH FILTER TO REDUCE FEEDBACK

Notching out instrument cavity resonance will eliminate the low frequency feed-

back problem completely. The advantages to using notching equalization are:

• The physical distance from the speaker will no longer be a factor for potential

low frequency feedback.

• The mic'ed instrument/speaker can remain

in phase,

maintaining a more nat-

ural and balanced response.

DISTANCE:

5’ 7"

PHASE INVERTED 180° PHASE INVERTED 180°

11’ 4" 17 ’ 22’ 7"

The PHASE switch on the ONBOARD BLENDER™ in effect electronically "moves" your instrument's

position relative to the speaker by inverting the phase 180° every time you flip it.

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Fishman Blender User Manual Page 10