Active Crossover Output Level Controls

Setting the output attenuators on active crossovers differs from other outboard gear in that they serve a different purpose. These attenuators allow setting different output levels to each driver to correct for efficiency differences. This means that the same voltage applied to different drivers results in different loudness levels. This is the loudspeaker sensitivity specification, usually stated as so many dB SPL at a distance of one meter, when driven with one watt. Ergo, you want to set these controls for equal maximum loudness in each driver section. Try this approach:

    Turn down all the crossover outputs except for the lowest frequency band, typically labeled "Low-Out." (Set one channel at a time for stereo systems.)
    If available, use pink noise as a source for these settings; otherwise use a frequency tone that falls mid-band for each section. Turn up the source until you verify the console is putting out the maximum system signal level (somewhere around the console clipping point.) Using an SPL meter (Important: turn off all weighting filters; the SPL meter must have a flat response mode) turn down this one output level control until the maximum desired loudness level is reached, typically around 100-105 dB SPL. Very loud, but not harmful. (1-2 hours is the Permissible Noise Exposure allowed by the U.S. Dept. of Labor Noise Regulations for 100-105 dB SPL, A-weighted levels.)

Okay. You have established that with this maximum system signal this driver will not exceed your desired maximum loudness level (at the location picked for measurement). Now, do the same for the other output sections as follows:

    Mute this output section -- do not turn down the level control; you just set it! If a Mute button is not provided on the crossover, disconnect the cable going to the power amp.
    Turn up the next output section: either "High-Out" for 2-way systems, or "Mid-Out" for 3-way systems, until the same maximum loudness level is reached. Stop and mute this output.
    Continue this procedure until all output level controls are set.
    Un-mute all sections, and turn off the test source.

Congratulations! You have finished correctly setting the gain structure for your system.

Now you are ready to adjust equalization and set all dynamic controllers. Remember, after EQ-ing to always reset the EQ level controls for unity gain as required. Use the Bypass (or Engage) pushbuttons to "A/B" between equalized and un-equalized sound, adjusting the overall level controls as required for equal loudness in both positions.