Cardioid Subs Are Magic

Subs 3.5ft apart

I spent some time this week learning about how to coax a cardioid response pattern out of PA subwoofers. It's pretty amazing how well it works. Here's the skinny:

  1. Grab Merlijn van Veen's Sub Array Calculator. Make sure you read the instructions and go over his examples, they're very helpful. I picked "gradient array" in my configuration but end-fire arrays are very interesting too (if you've got lots of subs sitting around).
  2. Pick the frequency you want to emphasize with your subs, i.e. a central peak for the resulting response. I picked 80hz though I tried a few different values to see what worked best for my setup, and a higher or lower value may work better depending on the response of your subs.
  3. Calculate a quarter wavelength for that frequency, which in my case is 3.5ft.
  4. Set your subs up so that one is directly in front of the other, and the fronts of the cabs are separated by exactly the quarter wavelength.
  5. Invert the polarity of the rear sub, and add a delay equal to another quarter wavelength (in my case, 3.12ms).
  6. Put high- and low-pass filters on both subs equal to the values recommended by the array calculator (though this is another area where you may end up tinkering some).
  7. Line the front sub up with your PA mains. The mains should have a high-pass equal to the low-pass you put on the subs.

Amazingly, after everything is tuned up, you can walk behind the subs and the low frequencies virtually disappear. I can imagine this will really help clear up the muddyness and overall stage level on our little stage, and especially on the large one!