User manual RANE RA 27

[. . . ] Just be sure that no green/red LED responds when pink noise is turned off (if they do, background noise is causing erroneous readings and pink noise should be turned up higher). USE ±3 dB DISPLAY SETTING FOR LOW FREQUENCY ADJUSTMENTS. The crest factor (peak response) of true pink noise causes considerable LED flutter in the ±l dB mode, making it difficult to adjust quickly. We recommend that the ±3 dB setting be used on frequencies below 500 Hz or so; use the ±l dB on the more sensitive mids and highs. [. . . ] Slowly turn the LEVEL control back counter-clockwise until all the green and red LEDs are off, and no background noise is showing on the display. You will now have to run the pink noise volume through the speakers loud enough to make sure that the LEVEL control is not turned clockwise (up) from this setting, otherwise the background noise will falsify the readings. PINK NOISE RUN-UP Turn down the mixer output controls before switching on the Pink Noise, so that you don't detonate your speaker cabinets. Now switch the PINK NOISE button ON on the RA 27 and turn up the mixer and EQ LEVEL controls slowly until you hear pink noise through the speaker(s). There is a Pink Noise Output Level Adjustment on the rear of the RA27 ­ use a 1/8" screwdriver to vary the amount of Pink Noise to the mixer if necessary. MICROPHONE PLACEMENT You should perform the pink noise test with at least two different test microphone locations for each separate channel of EQ. Since speaker dispersion characteristics can vary greatly, it is desirable to look at a couple of different areas with the mic to obtain an average for the entire listening area. If you are using one equalizer channel for both speakers (mono), place the mic in the center of the left half of the listening area and adjust for green LEDs with pink noise through the left speaker. Now move the mic to the center of the right half of the listening area, run pink noise through the right speaker and observe the analyzer LEDs: use the RA 27 LEVEL control to center the response for as many green LEDs lit as possible. For each frequency that requires a different adjustment than the left channel, note the original setting of the slider, then adjust it so that the green LED above it is lit and then note this new slider position: the final setting should be half-way between these two slider positions, resulting in an average response for the left and right channels. If you are running stereo, use two mic locations for each channel, averaging in the same manner if there are differences. Analyze one channel at a time. ANALYZER SETTINGS Select either the ±3 dB or the ±1 dB WINDOW on the analyzer. We recommend starting with the ±3 dB setting, then switching to the ±1 dB mode for fine-tuning frequencies above 400 or 500 Hz. The crest factor(peak response) of true pink noise causes considerable LED flutter in the ±1 dB mode below about 500 Hz, thus it is expedient to use the ±3 dB setting for these frequencies. INITIAL SYSTEM ALIGNMENT Before using the equalizer for adjustment, use the analyzer to align other equipment in the system (EQ should always be a last resort after you've corrected response problems everywhere else). With all EQ sliders flat (centered) adjust the electronic crossover frequencies and level controls (if used), passive crossover controls, speaker placement and alignment, etc. to get as many green LEDs lit as possible on the display. Only after this is done should you use the equalizer sliders to flatten the system (see next step). EQUALIZER SLIDER ADJUSTMENTS Now adjust each slider up or down as necessary until the green LED corresponding to the same frequency is lit; if the red is lit, move the slider down until green comes on. If yellow is lit, move the slider up to obtain green. If you can't get one or more green LEDs lit with their sliders fully boosted or cut, make a slight adjustment in the Pink Noise volume or LEVEL control to get these bands in the green. You will also notice that adjusting one slider may affect the LED readings on the adjacent bands: this is due to the presence of frequencies half-way between the two bands, which will be affected by both sliders. [. . . ] Feedback induced by specific stage mic/monitor speaker coupling can also be attenuated by leaving the stage mic turned up and running up the pink noise level through the monitor speaker until feedback occurs. Attenuate each feedback frequency, as indicated by the analyzer display, until the mic/monitor combination feeds back at two or more frequencies simultaneously. Usually the final EQ setting will be a compromise between a good monitor sound that doesn't get as loud, or a not-so-good monitor sound that gets louder before feedback. An RA 27 can be used as a driver alignment tool (see the AC 22/23/B Owners Manual) as well as a room-flattening equalizer. [. . . ]