Nuts and bolts of PA tuning part 2

Yesterday we covered the thought process in tuning the main speakers in our PA.  Today we’re going to discuss delay fills.

After starting with the main speakers, I work outward from there until we get to the speakers in the back of the room.  Often the first step after mains is downfills.  I like to work my way out from the mains because as I add more speakers to what I’m listening to, they all start to work together and I have to follow that energy rather than fight it.  Every change you make to one set effects everything else so you have to think holistically and experiment.

The key to making fill speakers work is two things – delay time and EQ.  If the main speakers are our starting point and benchmark that everything else must align to, fill speakers such as downfill or delays will normally arrive at either slightly different or perhaps greatly different times to your ear depending on where you are standing in the room.  The trick is to use delay so that speakers that are separated by 5 feet or 75 feet sound like they are all arriving at your ear at the same time and thus working together.  I use my software program to help calculate the necessary delay times, often times with a bit of trial and error in real world to nudge things forward or backward just a bit so it feels right.

After the delay time is right, I like to first turn off the speaker I’m getting ready to work with and just measure how everything else we’ve already optimized sounds in the location of the fill speaker.  This tells us what is missing sonically in this location from what we’ve already done and that is what we will focus on with EQ’ing the fill speaker.  I will high-pass the speaker so the low frequencies that are already hitting the area from the main speakers are not competing with additional stuff trying to come from the fill.  Now balance the sonic EQ of the fill so the response curve sounds as close to standing in front of the main speaker as possible.  Continue this process with each set of fills and eventually all parts of the system are operating at the same time.

As I said, this is a very high level discussion because the reality is that the process of tuning a PA is as much art as it is science.  For me, depending on the complexity of the system and the acoustics of the room it is installed in, there can also be a fair amount of experimentation & trial/error.  One of our largest rooms at newlifechurch.tv has a distributed audio system design – 4 main arrays in the front of the room with downfills below them and then a ring of delay speakers 2/3′s of the way back.  It took me three attempts at tuning this room before I arrived at a product that I’m reasonably happy with as a long-term starting point.  Each time I did it, I learned more about how all of the speakers interacted with each other, the acoustics of the room, and the result was less and less needed EQ each time.

In my experience with trying to get a great board mix for broadcast from the same console mixing FOH, a well-tuned PA is absolutely required to have any chance of success.