OEQ-1 Octave Equalizer Owner's Manual - Rockford Fosgate

OEQ- 1OCTAVEEQUALIZEROEQ-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 engineeringexpertise, handcraftmanship and critical testing procedures, we have created a wide range of products that reproduce music with all the clarity andrichness you deserve.For maximum performance we recommend you have your new RockfordFosgate product installed by an Authorized Rockford Fosgate Dealer, as weprovide specialized training through Rockford Technical Training Institute(RTTI). The length and nature of your warranty are dramatically affected ifyou install the product yourself. Please read your warranty and retain yourreceipt and original carton for possible future use.For your musical enjoyment, Rockford Fosgate offers everything from twochannel Punch amplifiers, the more powerful four channel Power Series amplifiers, to three lines of speakers: Pro Series , The Punch , and SeriesOne . In addition, we offer two, three, or four way speaker systems, andsubwoofer and full range enclosures. For sound reproduction at its best, weoffer 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, highoutput alternators, and many more accessories through our Perfect Interface division.To add the finishing touch to your new Rockford Fosgate image, order theRockford P.O.P., which includes everything from t-shirts and jackets, to keychains and neon hats.To get a free brochure on Rockford Fosgate products and Rockford P.O.P.,please call 602-967-3565 or FAX 602-967-8132.

INTRO DUCTIONThe Rockford Fosgate OEQ-1 is a quiet, flexible nine-bandequalizer designed to correct response errors in autosoundinstallations. As car stereo systems become more sophisticated, the unpredictable colorations of typical speaker installations are becoming less acceptable. The OEQ-1 offersa convenient method of solving response problems withoutsystem re-designs.lNine-Band High-Q Filter System(IS0 Center Frequencies)l 9dB Control Range Each Frequencyl 1/2 Octave Frequency Control Each FrequencylOver 90dB Signal-to-Noise Ratio (A-Weighted)lFully-Floating High-Voltage Power SupplyllDefeat Switch (Bypasses all circuitry)Jeweler’s Screwdriver Control AdjustmentsOEQ-11 DESIGNNINE-BANDS: Eight Octave-wide bands and one two-Octave band of boost and cut are employed in the OEQ-1. OneOctave bands are the minimum required for effective controlover the bass and midrange; the two-Octave-wide 12kHzband controls the very high “tingle” region where tonalperception is less critical.HIGH-Q FILTERS: Filter “Q” or quality factor is a measure ofthe “narrowness” of the filter response: a high-Q filter affectsa narrow band of frequencies and a low-Q filter affects a wideband. Most octave equalizers use relatively low-Q filters inorder to avoid large response ripples when all controls are atmaximum or minimum. However, the wide band of low-Qfilters allows adjustments made on one control to stronglyaffect the neighboring frequencies, especially at modestboost or cut. In addition, relatively narrow response problems cannot be fully cancelled by a wide-band filter.The rationale for reducing filter Q to avoid max-control rippleis in error, since it is a situation which realistically nevershould happen. By using relatively high Q (over 2.0), theOEQ-1 avoids much of the adjacent-band overlap that istime consuming to adjust out.

FREQUENCY SHIFT: When a high-resolution test instrument (one-third Octave RTA or swept tone analyzer) is used,it is common to find that a problem dip or peak is locatedbetween the band centers of the equalizer. The OEQ-I hascontrols to shift the center frequency of each band up ordown one-half octave, eliminating this frustrating problem.FULLY-FLOATING POWER SUPPLY: Most autosoundsignal processors use the battery voltage to power internalcircuitry. This practice leads to two potential problems:inadequate headroom and noise. The noise associated withdirectly battery-powered equipment arises from the presence of a direct ground path from circuitry to chassis. Thisprovides the potential for a ground loop, a path for alternatorwhine and electrical system noises to enter the system. Theheadroom issue resolves itself to a simple lack of voltage.Typical maximum voltages available from a battery aloneamount to about 3.5 Volts RMS. Many sources put out overone Volt RMS, leading to less than 11dB or headroom.The OEQ-1 employs a fully isolated 36-Volt (plus and minus18 Volt) supply. There is no DC path to chassis ground, soground loops are eliminated. The high voltages allow preand de-emphasis for the most sensitive frequencies lead toexceptional noise performance.EQUALIZING WITH A REAL TIME ANALYZERFor best resolution, a 30-band (1/3 Octave) Real-TimeAnalyzer (RTA) or a swept spectrum analyzer with 1/3Octave resolution should be used. A lo-band, l-Octaveresolution 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 allowsthe equalizer to be adjusted from a convenient location.NOTE: If you would like further advice on acquiring theabove mentioned support equipment, feel free to call Rockford at 602-967-3565.Step 1: The RTA or analyzer microphone should be set upnear the driver’s listening location. Microphone placementwill have a significant effect on frequency response, andmoving the microphone around in the driver’s area will givea good idea of overall response.2

Step 2: Feed one channel of the Octave Equalizer with pinknoise from the pink noise generator.Step 3: Evaluate the unequalized response. Major systemproblems, 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) willresult in overdriven amplifiers and speakers, and should notbe attempted.Step 4: Adjust equalizer for the system response desired.Since adjacent bands interact with each other, you will needto go back and forth between frequencies to get the bestbalance.Step 5: Move the microphone to the opposite side, changethe pink noise channel, and equalize for the same responseas Step 4.SOME SUGGESTIONSllllIt is best to equalize one channel at a time. Trying to set upboth channels at once confuses which channel is producingthe results.If you can identify a response problem by ear, move themicrophone to a point that reveals the problem. Mikeplacement can have a very large effect on response, andsome microphone positions will obscure problems insteadof showing them.The audible effect of response problems is a product of boththe magnitude of the error and its width. A 9-dB “hole” one/third octave wide is less audible than a 2-dB “dip” twooctaves wide. Try for an average response equally aboveand below the desired response over each octave span.The human ear averages the overall sound-field responseby complex physiological and psychological pro-cessing. Asingle microphone only hears at one point, which must beselected to represent as closely as possible the overallsound field. Since tonal perception is most influenced bythe nearest source, we usually equalize each side separately. The mike is set up at the driver’s listening location,facing forward, and the left channel is equalized. Then themike is set up at the passenger’s location and the rightchannel is set up to match the left. This procedure usuallygives good results.3

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EQUALIZER FREQUENCY SHIFT1601608080

POWER WIRINGThe black wire should be chassis-grounded to a solid metalground. The red wire should be connected to the sourceunit’s auto-antenna or accessory lead. If present, the whitewire should be connected to the battery or another positivevoltage source.EQUALIZATION GOALSThe primary goal of the equalizer set-up is to produce asmooth response approaching a desired curve, eliminatingor reducing peaks and valleys in the system response.Systems could be equalized for a perfectly flat response, buta flat response sounds very thin and bodiless. A betterapproach is to attempt a final response similar to the roomresponse of a good home speaker.Figure 3, shows some typical “good-sounding” system response curves. Curve “A” is a good general-purpose goal.Curve “C” with increased bass will give more impact on rockand roll, while “B” would sound more natural for symphonicmusic. Curve “D” illustrates reduced roll-off in the mids andhighs.The OEQ-1 is deliberately restricted to 9dB of boost or cutper band. This is meant to discourage attempts to correctlarge system response problems with the equalizer. Systemresponse errors greater than about 6dB over a span of anoctave of more should be corrected elsewhere in the system,by correcting speaker or amplifier problems. Excessive useof equalization is likely to overdrive amplifiers, speakers, orother components.INPUT AND OUTPUT LEVELSThe OEQ-1 is designed to be used at preamp-output levelsonly (500 to 750 mVRMS). Higher input levels may overloadthe circuitry and must be attenuated. The OEQ-1 is designedto have a gain of one (output equal to input) when allpotentiometers are centered.DEFEAT SWITCHThe Defeat Switch completely disconnects all electronics inthe signal path and connects the input directly to the output.6

OEQ-1 SPECIFICATIONSInput level:750 mV RMSInput Impedance:20 k OhmsOutput level:750 mV RMSOutput Impedance:500 OhmsSignal-to-Noise Ratio:Over 90dB (A-Weighted)Distortion:Under .01% THD NoiseFilter Q:2 typical (Bands l-8); 1 (Band 9)Power Required:Under 1 Amp at 12 Volt nominalDimensions:4.75” wide x 8.65” long x 1.25” high120.6mm x 219.7mm x 31.75mmWeight:1 lb. 13 oz.822 gramsSpecficationssubject to change without notice.8