Cardioid Subs Are Magic
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:
- 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).
- 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.
- Calculate a quarter wavelength for that frequency, which in my case is 3.5ft.
- 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.
- Invert the polarity of the rear sub, and add a delay equal to another quarter wavelength (in my case, 3.12ms).
- 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).
- 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!