User manual RANE AC 23B

[. . . ] OPERATORS MANUAL AC 23B ACTIVE CROSSOVER QUICK START Labels above the controls refer to the unit being operated in the 2- or 3-Way Stereo mode. Labels below the controls refer to the unit being operated in the 4- or 5-Way Mono mode. The AC 23B is a fully balanced version of the popular AC 23 and is equipped with 3-pin (XLR-type) connectors instead of the standard ¼" TRS jacks. A STEREO/MONO switch has been added to the AC 23B and should be set appropriately. [. . . ] 2 Corrected In-Phase Axis Response With Electronic Time Delay on Low Frequency Driver Time Delay Adjustment Using Realtime Analyzer & Pink Noise This method outlines the use of a realtime analyzer, pink noise generator and flat response microphone to set crossover time delay. Some references will be made to the Rane RA 27 realtime analyzer for those with the intelligence and good taste to use one of these regularly. We recommend using a 1/3 or 2/3 octave analyzer as either of these is more likely to match your specific crossover points than a one-octave analyzer. And it is important to match the analyzer to the crossover point as closely as possible for proper phase alignment, otherwise the analyzer readings may be misleading. Manual-11 physically move the high driver farther forward until the display shows +3 dB (red). The amount of displacement correction available from the Delay depends on the actual crossover frequency: the higher the frequency, the less amount of correction capability. If the drivers are built into a single cabinet and/or it is impossible to change relative positions, then you will have to obtain additional external delay to achieve proper phase alignment. If turning the MID DELAY control up makes the display reading decrease instead of increase, this means that the high driver is actually in front of the mid driver; adding delay to the mid driver only worsens the situation. Try to move the high driver back as far as possible without losing stability in balancing the speaker stack. You may want to raise it up as well to restore dispersion close to the stack. If you cannot move the high driver, then you will have to use an additional delay source to align the high and mid drivers. The built-in delay system in the AC 23B is designed to accommodate the majority of common speaker configurations; if you encounter confusion or difficulty with your particular system, it is best to consult your dealer or the Rane factory for assistance. If this decrease in the display due to the DELAY control occurs at a low frequency crossover point below about 150 Hz, set the DELAY control to minimum and leave it there. Frequencies below 150 Hz are actually omnidirectional, so that phase misalignment is virtually inaudible below this point. Subwoofers will often possess long folded or straight horns, resulting in the diaphragm being well behind the rest of the stack. Most authorities agree that phase alignment of subwoofers is unnecessary. Lower the microphone until it is vertically midway between the mid and low drivers. Repeat steps 2 through 5, using the crossover LEVEL control, MUTE switch and next DELAY control. You may start each series of steps 2 through 5 at a different volume as necessary--but once the Levels are set in step 3 do not alter these until step 5 is completed. Once all of the crossover DELAY controls are set, then adjust the output LEVEL controls as outlined on page Manual-15. Time Delay Adjustment Using SPL Meter & Tone Generator Now that good quality realtime analyzers are becoming more affordable and easier to use, there are few reasons why one of these should not be regularly used in any sound system. If an analyzer is simply not available or for some reason inappropriate, an accurate delay setting can be obtained by using a straightforward SPL meter (obtainable at most local electronics and some hi-fi stores) and some kind of variable tone generator. In order to exclude the effect of room acoustics and imperfect driver response, only the crossover frequencies are to be emitted (one at a time) by the tone generator. First the highest crossover frequency is run through the crossover and each of the two speakers sharing the crossover point is set separately to an arbitrary 0 dB level on the SPL meter. [. . . ] This modification should only be attempted by an experienced technician. It is important to know the 3 dB down point of the CD driver's frequency response. The manufacturer of your driver should be able to supply you with a chart showing a frequency response curve. Find the point where the high end starts to roll off, and look for the point on the chart that is 3 dB down from that point (toward the right, as the higher frequencies roll off). [. . . ]