Rockford Fosgate OEQ-1 User manual

OEQ- 1
OCTAVE
EQUALIZER

Dear Customer,
Congratulations on your purchase of America’s finest car audio components .
At Rockford Fosgate we are committed to musical reproduction at its best,
and we are pleased you chose our product. Through years of engineering
expertise, handcraftmanship and critical testing procedures, we have cre-
ated a wide range of products that reproduce music with all the clarity and
richness you deserve.
For maximum performance we recommend you have your new Rockford
Fosgate product installed by an Authorized Rockford Fosgate Dealer, as we
provide specialized training through Rockford Technical Training Institute
(RTTI). The length and nature of your warranty are dramatically affected if
you install the product yourself. Please read your warranty and retain your
receipt and original carton for possible future use.
For your musical enjoyment, Rockford Fosgate offers everything from two
channel Punch®amplifiers, the more powerful four channel Power Series™
amplifiers, to three lines of speakers: Pro Series™,The Punch®, and Series
One
™
. In addition, we offer two, three, or four way speaker systems, and
subwoofer and full range enclosures. For sound reproduction at its best, we
offer signal processors: equalizers, pre-amps, and crossovers.
To ensure overall installation quality, Rockford provides top quality wire,
connectors, carpet, grille cloth, speaker grilles and amplifier shrouds, high
output alternators, and many more accessories through our Perfect Inter-
face® division.
To add the finishing touch to your new Rockford Fosgate image, order the
Rockford
P.O.P., which includes everything from t-shirts and jackets, to key
chains and neon hats.
To get a free brochure on Rockford Fosgate products and Rockford P.O.P.,
please call 602-967-3565 or FAX [phone].

INTRO
OEQ-11
DUCTION
The Rockford Fosgate OEQ-1 is a quiet, flexible nine-band
equalizer designed to correct response errors in autosound
installations. As car stereo systems become more sophisti-
cated, the unpredictable colorations of typical speaker in-
stallations are becoming less acceptable. The OEQ-1 offers
a convenient method of solving response problems without
system re-designs.
l Nine-Band High-Q Filter System
(IS0 Center Frequencies)
l ±9dB Control Range Each Frequency
l ±1/2 Octave Frequency Control Each Frequency
l Over 90dB Signal-to-Noise Ratio (A-Weighted)
l Fully-Floating High-Voltage Power Supply
lDefeat Switch (Bypasses all circuitry)
l Jeweler’s Screwdriver Control Adjustments
DESIGN
NINE-BANDS: Eight Octave-wide bands and one two-Oc-
tave band of boost and cut are employed in the OEQ-1. One-
Octave bands are the minimum required for effective control
over the bass and midrange; the two-Octave-wide 12kHz
band controls the very high “tingle” region where tonal
perception is less critical.
HIGH-Q FILTERS: Filter
“Q” or quality factor is a measure of
the “narrowness” of the filter response: a high-Q filter affects
a narrow band of frequencies and a low-Q filter affects a wide
band. Most octave equalizers use relatively low-Q filters in
order to avoid large response ripples when all controls are at
maximum or minimum. However, the wide band of low-Q
filters allows adjustments made on one control to strongly
affect the neighboring frequencies, especially at modest
boost or cut. In addition, relatively narrow response prob-
lems cannot be fully cancelled by a wide-band filter.
The rationale for reducing filter Q to avoid max-control ripple
is in error, since it is a situation which realistically never
should happen. By using relatively high Q (over 2.0), the
OEQ-1 avoids much of the adjacent-band overlap that is
time consuming to adjust out.

FREQUENCY SHIFT: When a high-resolution test instru-
ment (one-third Octave RTA or swept tone analyzer) is used,
it is common to find that a problem dip or peak is located
between the band centers of the equalizer. The OEQ-I has
controls to shift the center frequency of each band up or
down one-half octave, eliminating this frustrating problem.
FULLY-FLOATING POWER SUPPLY: Most autosound
signal processors use the battery voltage to power internal
circuitry. This practice leads to two potential problems:
inadequate headroom and noise. The noise associated with
directly battery-powered equipment arises from the pres-
ence of a direct ground path from circuitry to chassis. This
provides the potential for a ground loop, a path for alternator
whine and electrical system noises to enter the system. The
headroom issue resolves itself to a simple lack of voltage.
Typical maximum voltages available from a battery alone
amount to about 3.5 Volts RMS. Many sources put out over
one Volt RMS, leading to less than 11dB or headroom.
The OEQ-1 employs a fully isolated 36-Volt (plus and minus
18 Volt) supply. There is no DC path to chassis ground, so
ground loops are eliminated. The high voltages allow pre-
and de-emphasis for the most sensitive frequencies lead to
exceptional noise performance.
EQUALIZING WITH A REAL TIME ANALYZER
For best resolution, a 30-band (1/3 Octave) Real-Time
Analyzer (RTA) or a swept spectrum analyzer with
1/3-
Octave resolution should be used. A lo-band, l-Octave
resolution RTA will give decent results, but is harder to use.
Either RTA method will require a pink noise generator.
An extender cable is available from Rockford which allows
the equalizer to be adjusted from a convenient location.
NOTE: If you would like further advice on acquiring the
above mentioned support equipment, feel free to call
Rock-
ford at 602-967-3565.
Step 1: The RTA or analyzer microphone should be set up
near the driver’s listening location. Microphone placement
will have a significant effect on frequency response, and
moving the microphone around in the driver’s area will give
a good idea of overall response.
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Step 2: Feed one channel of the Octave Equalizer with pink
noise from the pink noise generator.
Step 3: Evaluate the unequalized response. Major system
problems, for instance large response “holes” or “peaks”,
should be solved by correcting speaker or system problems.
Trying to equalize out large response errors (over 6dB) will
result in overdriven amplifiers and speakers, and should not
be attempted.
Step 4: Adjust equalizer for the system response desired.
Since adjacent bands interact with each other, you will need
to go back and forth between frequencies to get the best
balance.
Step 5: Move the microphone to the opposite side, change
the pink noise channel, and equalize for the same response
as Step 4.
SOME SUGGESTIONS
l It is best to equalize one channel at a time. Trying to set up
both channels at once confuses which channel is producing
the results.
l If you can identify a response problem by ear, move the
microphone to a point that reveals the problem. Mike
placement can have a very large effect on response, and
some microphone positions will obscure problems instead
of showing them.
lThe audible effect of response problems is a product of both
the magnitude of the error and its width. A 9-dB “hole” one/
third octave wide is less audible than a 2-dB “dip” two
octaves wide. Try for an average response equally above
and below the desired response over each octave span.
l The human ear averages the overall sound-field response
by complex physiological and psychological pro-cessing. A
single microphone only hears at one point, which must be
selected to represent as closely as possible the overall
sound field. Since tonal perception is most influenced by
the nearest source, we usually equalize each side sepa-
rately. The mike is set up at the driver’s listening location,
facing forward, and the left channel is equalized. Then the
mike is set up at the passenger’s location and the right
channel is set up to match the left. This procedure usually
gives good results.
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EQUALIZER FREQUENCY BANDS
20k
10k
j.lk
!.6k
1.3k
320
160
80
40
20
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Y
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20k
10k
5.lk
2.6k
1.3k
640
320
160
80

EQUALIZER FREQUENCY SHIFT
160 160
80 80

POWER WIRING
The black wire should be chassis-grounded to a solid metal
ground. The red wire should be connected to the source
unit’s auto-antenna or accessory lead. If present, the white
wire should be connected to the battery or another positive
voltage source.
EQUALIZATION GOALS
The primary goal of the equalizer set-up is to produce a
smooth response approaching a desired curve, eliminating
or reducing peaks and valleys in the system response.
Systems could be equalized for a perfectly flat response, but
a flat response sounds very thin and bodiless. A better
approach is to attempt a final response similar to the room
response of a good home speaker.
Figure 3, shows some typical “good-sounding” system re-
sponse curves. Curve “A” is a good general-purpose goal.
Curve “C” with increased bass will give more impact on rock
and roll, while “B” would sound more natural for symphonic
music. Curve “D” illustrates reduced roll-off in the mids and
highs.
The OEQ-1 is deliberately restricted to 9dB of boost or cut
per band. This is meant to discourage attempts to correct
large system response problems with the equalizer. System
response errors greater than about 6dB over a span of an
octave of more should be corrected elsewhere in the system,
by correcting speaker or amplifier problems. Excessive use
of equalization is likely to overdrive amplifiers, speakers, or
other components.
INPUT AND OUTPUT LEVELS
The OEQ-1 is designed to be used at preamp-output levels
only (500 to 750 mVRMS). Higher input levels may overload
the circuitry and must be attenuated. The OEQ-1 is designed
to have a gain of one (output equal to input) when all
potentiometers are centered.
DEFEAT SWITCH
The Defeat Switch completely disconnects all electronics in
the signal path and connects the input directly to the output.
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OEQ-1 SPECIFICATIONS
Input level: 750 mV RMS
Input Impedance: 20 k Ohms
Output level: 750
mV RMS
Output Impedance: 500 Ohms
Signal-to-Noise Ratio: Over 90dB (A-Weighted)
Distortion: Under .01% THD + Noise
Filter Q: 2 typical (Bands l-8); 1 (Band 9)
Power Required: Under 1 Amp at 12 Volt nominal
Dimensions: 4.75” wide x 8.65” long x 1.25” high
120.6mm x 219.7mm x 31.75mm
Weight: 1 lb. 13 oz.
822 grams
Specfications subject to change without notice.
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