Why you need to rethink imaging in the audio system
Ok, I think it is time to talk about imaging audio.
Everyone likes to discuss the performance of a loud speaker on multiple fronts but, do we ever really think about how an audience perceives the image itself? Not enough apparently. In the past few years I have been rethinking how we design performance audio systems for better imaging and clarity.
Let’s consider how we as humans hear things in real life. When we are walking down the street, we hear many things, especially on busy sidewalks. When you hear something stand out, your head turns laterally to that direction. Left or right, you will naturally turn in that direction. Looking up is considerably more effort, although the head will tilt up so the ears can be in a more natural position to hear the source of the sound. Your ears want to be on axis especially when it comes to high frequencies. You will always turn your head to hear something.
All in the Head?
So, why do we insist on putting audio over peoples’ heads and still expect a good, full broadband image? Is it that we are all tied to what an architect might be giving us for space or is it that we have always done it this way? My real pet peeve is thinking an LCR system might actually work. Did we really think this was a good idea? Do you think a center source 35 feet above the audience’s heads will bring you a center image to the stage where you need it most? It is probably not a great idea and we do it all the time. Well, not me. I don’t buy into the promise of LCRs and haven’t for a very long time.
How about trying something for fun? Set up a good on-axis stereo source for a few students, play some good dynamic material and ask them to find the hole in the center. That would be a trick question.
Recently I have had the chance to put in a system that is left-right on a platform and almost completely on axis to the audience with a single sub in the center underneath the stage area. What hit me right away when I was commissioning this system was how natural it sounded and how all the voices seem to be coming from where they should be coming from: the platform. I also noticed that because this is a left-right system and the majority of the audience was now between the speakers, I could actually start panning the images. The result was magic. It was like mixing in a controlled studio environment. Then it hit me. The speakers are in the proper position for the brain to actually interpret what it sees: “Full frontal and on axis.” There were no speakers in the air for the brain to have to compensate for as well as acoustics to hear through. Not only was the image correct, the amount of acoustic 2nd and 3rd order reflections confusing the brain was down to almost an irrelevant level.
Almost everything you see today coming from most designers is probably not an optimum way to deploy a performance audio system. Just in the way vertical line arrays made us rethink how we distribute sound, we now need to take it one step further and make imaging a priority when designing so the audience perception takes priority. Vertical line arrays definitely help but keeping them smaller, lower and more on axis will be the key for better imaging.
Just a little something to think about the next time a project comes up.
By Bob Langois