Audio Control EQS Owner's Manual page 15

There is no one curve that will satisfy every person, as we
all have different tastes.
How else can you explain Liberace or rice cakes? The key
is to use your EQS to help balance your system from one
frequency to the next and give your speakers the sparkle,
sizzle, detail or punch that the acoustics of the car have
compromised.
3. You will want to start equalizing by removing or
cutting any large bumps, peaks, or areas with too much
energy at a particular frequency. Next, boost the ranges that
do not have enough energy. We strongly recommend that
you cut or decrease energy before you boost.
4. Although the plethora of knobs on your EQS can be
intimidating, fear not as they were designed to give enough
control to maximize your systems performance but not
enough to get you in trouble. Here is an explanation of the
key areas you should focus on:
Sub-bass: 100 Hz and below – A car without bass is
like a day without sunshine... unless you live where we do
because most of the days in the Pacific Northwest do not
have sunshine. This area is one of the more critical although
it is also one of the most difficult to properly reproduce.
Most people refer their bass frequencies to be 6 to 9 dB louder
than the rest of their system, although there are some crazy
folks that prefer their bass substantially louder. They key in
this area is to have enough speakers and power to produce
the amount of bass you desire but don't use the controls on
the EQS to try and force your speakers to produce sounds
they can't. Too much bass boost creates a condition called
"speakerus explodus", which is not pretty to hear or watch.
Midbass: 100 Hz to 300Hz – The phrase, "too much of
a good thing" can certainly apply to the midbass frequencies.
This is the transition area of the audio spectrum that is an
octave above your sub-bass frequencies and several octaves
below your midrange. Most autosound systems have too
much midbass due to the fact that speakers mounted in the
doors or kick panels cause resonance's or peaks in the
response curve. These peaks in the midbass can actually
mask or block sounds in the all-important midrange area
causing your system to sound dull or lifeless.
Midrange: 300Hz to 3Khz – Musical instruments,
vocals, mid-range percussion and many things we associate
with imaging and staging happen in this area of the band-
Owner's Enjoyment Manual 13