Neutral Or Tilted?
There are different schools of thought on a starting point for a system. With a flat transfer function from 20 Hz to 20 kHz, we may find that our mix sounds a little thin, so many engineers (including myself) mixing rock or pop music will agree that the level of the sub bass and low-frequency section should be turned up or “tilted” by some degree to sound the way we like it: full and round.
However, a flat frequency response from 200 Hz or so all the way up to 20 kHz should produce good initial results throughout the rest of the spectrum. Again, the point here is that the “standard” set by this flat response is that the system sounds like the console, so if you have that side of things sorted, the PA should produce a good neutral “canvas” for your artistic masterpiece.
It’s worth noting that other styles of music, such as classical and jazz, can be well suited to a completely flat transfer function. So too can spoken word and corporate speech-based content, with an aux send of music/video roll content only to avoid an excess of low-frequency energy that can mess with lavalier or headset mics.
Getting back to festivals, I recall a day many years ago when I was the FOH engineer for one of the six bands on the bill for a festival in the Boston area. We were in slot five, so as we were backstage readying our backline gear on risers and miking up, I was able to hear several bands performing before us.
As the first band was introduced, a long, howling low-end stream of feedback rung out for at least 10 seconds before the engineer was able to right the ship. Things were still unstable in the lows for a couple more songs, and then it started to shape up. When the second band fired up, the exact same thing happened. Then the third, and also the fourth. Something seemed very wrong.
Solid Starting Point
When I finally had my chance to get out front and “prep” my console for the show (this was one of those days when I had to spin it up from scratch on an analog console with no line check in the PA), I made a very conscious decision to roll all of the high-pass filters (HPF) on the input channels up much higher than I normally would – I often run vocal HPFs between 160 Hz and 200 Hz based on the way I tune my systems (which, as noted above, is flat response from 200 Hz to 20 kHz with a 12 dB boost in the sub centering around 60 Hz).
Getting back to this particular show, however, I started at a very “safe” 300 Hz or so, and even engaged some HPFs on inputs I normally leave untouched, such as floor toms and bass guitar. When we began, I was absolutely stunned that the same low-end rumble started right out of the gate for me too.
It took a little while to roll those HPFs up even higher and to do some cutting on the system EQ, but when I finally had a chance to catch my breath, I turned to the festival system tech for the day, and in as kind of a manner as I could muster said, “You have got to be kidding me!”
Afterward, I had a chance to talk to the house audio personnel, asking who tuned the PA as well as how much were the subs and lows turned up in comparison to the mids and highs. They just kind of shrugged in response, because the answer was pretty obvious: way too much.
So the next time you’re in a situation where you’re mixing a show on a system that you haven’t had a chance to hear prior to putting the mix through it, ask yourself this: “What starting point would I like if given the choice, and could we possibly agree that we could all benefit from more dialog in the audio community regarding a standard tonality for multi-act festival shows moving forward?”