By Michael Lawrence • March 11, 2019 Editor’s Note: Approaches in audio are as unique and plentiful as the people working in the field. With the basic principles of audio well in hand, the way forward for each individual is shaped by her/his individual experiences. Viewpoints is designed to illustrate the varied approaches and schools of thought on relevant trends and interesting topics. To kick things off, technical editor Michael Lawrence discusses the topic of sound system response “tilt” with system tuning guru Jim Yakabuski. ML: Jim, you and I have been emailing back and forth about this since it was a Roundtable topic several months ago, so here we go: This is largely a matter of preference, but there’s one thing I can point to as an objective justification for a flat-tuned PA system. I’ve written in the past about an idea that is based on a Dave Rat concept – each EQ in the system has its own job – channel EQ for adjusting performer, microphone, and anything else related to inputs. Bus EQ for the whole mix, system EQ for the PA itself, etc. I like the example that if the subs are set too low, you will likely have to run up the low frequency on all the input EQs to get the sound you’re seeking. Now, if you solo the mix on headphones, it sounds extremely bass heavy at all the points in between. However, if the change is made at the system processor – the proper place to correct balance issues with the system – now you can cue the signal or take a board recording at any point and it will always sound correctly balanced. In addition, a board mix or reference recording sounds correct when played back, no different than a pair of studio monitors. A board mix from a system with a massive sub bump, on the other hand, will sound anemic on a reference system, or when soloed on cans. So it violates the “sound correct at every point” concept. JY: I’ve been thinking about this the last couple days. You are 100 percent spot on with this thinking and this practice of “no tilt” in the low end. I’ve heard that this method is endorsed by Showco/Clair famed engineer Howard Page but I’ve never really put this into practice myself when mixing music. To play a little bit more of the “devil’s advocate” and to enforce what I’ve found for decades when using sound systems tuned by other system people in festival and one-off scenarios, I think it lands somewhere between “theory” and “reality.” The theory that you describe with a system that has minimal or zero sub bump or low-end tilt is that your channel EQ will include more low-end content and less high-pass filtering (HPF), which then makes the entire mix sound more full and along the lines of what most shows sound like. And as you said, console recordings sound fuller, and headphones or studio monitors sound almost identical to the PA system. I’ve attempted to go down this road many times and to minimize the sub bump to almost nothing. It works pretty well when I have control over the sound system. The problems arise when you’re using a variety of PA systems in a variety of scenarios tuned by God knows who… The theory that everyone drives their cars on the highway at 65 miles per hour (mph) is great but if everyone is zooming past you at 80 mph, it makes you uncomfortable. I find that many large-format loudspeaker systems have stock presets for their boxes that have quite a low end and sub tilt, so if you’re one of the acts on a festival gig and you don’t get any time to tune the rig for your show, your console mix is going to sound way too sub heavy and you’ll have to “undo” all of the bass tilt in the rig. I’ve come to the compromise of setting the console channel EQ and HPFs based on sound system EQ flat from 200 Hz to 20 kHz with a +12 dB tilt in the sub centered at 60 Hz. This method seems to average out with most stock PA presets and festival sound system tunings. ML: I think the key phrase here is “when I have control over the sound system.” That’s the big factor that really affects how closely a previous mix or board recording will match what it’s supposed to sound like. That works in both directions, too – you might have a mix ready for a “tilted” system that will sound equally crazy when played back on a flat one. So I guess the theme here is consistency, no matter what tilt you prefer, just achieving it every night. There’s an extra factor here of the room and how much LF builds up. That changes from night to night, inside to outside, and affects the perceived tilt as well. And I think the other aspect is, like we said, convenience. Headroom considerations aside, mix engineers will do whatever they need to do to get things to sound right at their location. It’s “self-calibrating” so it just becomes a matter of how much filtering at the desk is required to do that. Practically speaking, music has a tilted spectrum that is remarkably consistent over genre, and so that tilt has to come from somewhere, either at the console or in the system DSP. This is also where I tune speech reinforcement systems flat but let the music systems tilt up a little, so there’s that convenience consideration again: What are we putting through this system? Music has an LF run-up while with speech we’re generally cutting it away. I think we’re agreed on all counts – it would be interesting to do a long term spectral average of board mix versus reference mix and try to visually “isolate” the tilt of the PA every night and get some long term data. JY: All good points. I’m sure if we asked 50 engineers, we’d get many preferences on “tilt” – yes/no and how much! Like you, I tune speech very flat when I’m working a corporate event and use an aux bus for the sub energy that I need for video rolls and music. When mixing music, I tune to the tilt mentioned earlier and I have my subs on a matrix so I can simply adjust the level to fit with the mains and extend until I see the shape I’m looking for via (Rational Acoustics) Smaart. In addition to serving as technical editor of LSI/PSW, Michael Lawrence is an independent front of house engineer and system tech who can be reached via precisionaudioservices.com. Jim Yakabuski has worked for well over three decades as a live sound engineer for a wide range of top artists. About Michael Michael Lawrence Michael Lawrence is an independent FOH engineer and system tech. He is also the technical editor of various pro audio publications. Send him your thoughts at [email protected] http://precisionaudioservices.com Comments Have something to say about this PSW content? Leave a comment! Cancel reply Scroll past the ”Post Comment” button below to view any existing comments. Your email address will not be published. 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