14
About Equalization
The Hartke AC75 or AC150 Acoustic ampli-
fier gives you enormous control over shaping
the sound of your acoustic rig, using a pro-
cess called equalization. To understand how
this works, it’s important to know that every
naturally occurring sound consists of a broad
range of pitches, or frequencies, combined
together in a unique way. This blend is what
gives every sound its distinctive tonal color. EQ
controls allow you to alter a sound by boosting
or attenuating specific frequency areas—they
operate much like the bass and treble controls
on your hi-fi amp, but with much greater preci-
sion. The AC75 or AC150 provides you with one
most effective tool for shaping the overall tone
of your Acoustic sound; a Graphic Equalizer
providing 12 dB of cut or boost in five narrow
frequency bands.
The five-band graphic equalizer provides
seven sliders, each corresponding to a single
narrow frequency band (100Hz, 315Hz, 1kHz,
3.5kHz and 10kHz.). This allows you to “draw”
the desired tonal response of your system.
When a slider is in its center position (“0”), it
has no effect. When it is moved above center
(towards “+12”), the particular frequency area is
being boosted; when it is moved below center
(towards “-12”), the frequency area is being
attenuated. We carefully selected these frequen-
cy areas because they have maximum impact
on acoustic signals. For example, the lowest
slider (100 Hz) affects the very lowest audible
frequencies (in fact, most humans cannot hear
below 20 Hz), while the highest four sliders
affects the mid-range and high frequencies.
To find out how each graphic equalizer slider
affects the sound of your particular acoustic,
start with all five bands flat (that is, all five slid-
ers at their “0” center position).
