Rane AC 22S Operation Manual - Page 11

iv. 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 then only worsens the situation. There are a couple of ways to deal with this: a. 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 obtain an additional delay source to align the high and mid drivers, such as the Rane AD 22B. The built‑in Delay system in the AC 22S 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. b. 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. Otherwise you will have to obtain additional delay equipment to align these to the rest of the system. 6. 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, adjust the output LEVEL controls as outlined in the Setting Levels Section on page Manual-12. Time Delay Adjustment Using an 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 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. When both drivers emit the crossover tone simultaneously, the combined response should read +3 dB higher on the meter. If the drivers are not phase aligned, some cancellation will occur on‑axis, resulting in a combined response less than +3 dB. Turning the DELAY control up causes the lower frequency driver to electronically move backward until the SPL meter reads +3 dB; then the two drivers are electronically aligned and the on‑axis cancellation is eliminated (see Figure 2 on page 6). This procedure is then repeated for the next lower crossover point(s). STEP BY STEP PROCEDURE A 3-Way mode consisting of high, mid and low drivers is used here as an example. For other configurations, use the same procedure starting with the highest crossover point and repeat steps 2 through 5 for each lower crossover point. 1. Set the tone generator to the highest crossover frequency and plug it into the Input of the crossover. Turn all crossover LEVEL controls fully down. 2. Position the SPL meter (microphone) about 15 feet in front of the speakers and at a height about midway between the high and mid drivers. It is very important that the meter remain in exactly the same position throughout the test, so affix it to a mic stand, small tree or other stable object. Set the switches on the SPL meter to C-weighting, slow. Be sure to minimize background noise (air conditioners, fans, traffic, wild animals, etc.) as these will effect the meter reading. 3. Slowly turn up both the crossover MASTER and MID LEVEL controls until the tone is heard through the mid driver. Adjust the SPL meter control and/or the crossover LEVEL controls until you obtain a 0 dB reading on the meter. Verify that no sound is coming from any other speakers except the mid driver. 4. Now press in the MID MUTE switch on the crossover so that the tone is removed from the mid driver. Without re‑adjusting either the meter or the crossover MASTER or MID LEVEL controls, turn up the HIGH LEVEL control until the tone coming from only the high driver reads 0 dB on the SPL meter. Manual-8