Since I’m carrying extra subwoofers on this tour, my daily task is to make them play nicely with the house subwoofers. Some days this is easier than others. Luckily the Clair BT218’s that we are carrying are just simple front loaded dual 18’s, and it’s very easy to make them cooperate with house subs. My “ideal” deployment with the BT218’s is a mono block in front of the stage. I say “ideal” because I can’t do any fancy subwoofer arrays on this tour. However, I can eliminate some of those annoying power alleys, and I can get the most impact out of my subs in the center. Additionally, when I have a separate send for the house subs, I can delay them further and steer the LF as needed.
Here’s one of the various house systems and my subwoofer deployments this tour:
How does one go about aligning subwoofers? The process itself really isn’t that complicated, it’s just being able to figure out if the measurement you’ve taken actually means something. The first step of the process simply involves capturing the house subs, and seeing what they look like. Here’s a screenshot from today, where the house system was an older EV X-array rig:
Some days, depending on the type of subwoofer and phase response, I’ll end up high passing it or EQ’ing as needed. This sub however was already pretty good looking out of the gate.
The next step is to shoot my subs and see what kind of delay time and phase response I end up with.
Once I get the phase to smooth out, I’ll subtract the delay time of my subs from the house subs and that should give me the “golden number.” I forgot to write down the delay times today, but I know I needed 10ms of delay for my subs to line up with the house subs. Remember, we’re not really looking at the magnitude response here, but mainly the phase response. Obviously we want the magnitude response to improve as I add my subs in, but I’m more worried about a smooth phase response. Here’s the combined subwoofer’s response:
Everything looks good together, the phase stays smooth, the magnitude response looks good and most importantly, it sounds louder. One thing to really take into consideration is that these are not perfect measurements by any means. They are down and dirty in sometimes less than ideal circumstances. It’s my job to figure out what looks “good enough” in a short frame and make it work for my show.
After I phase align the subwoofers, the listening process begins. I start with pink noise and punch my subs in and out to make sure the LF is actually getting louder. Once that is confirmed, I’ll play some tracks. Walking the room, I’ll look for nodes and power alleys with and without my subs, and I’ll listen up close to make sure the transition from their subs to mine is smooth. A lot of times, I’ll end up playing with the delay a little more to spread the LF out, tighten it up, or to steer the LF.
When it’s all said and done, the addition of my extra subs adds another dimension to the show, which adds more energy to the crowd and gives me the impact I’m looking for.