Any trouble you do run into because of boundary interference is better handled with careful absorption and the simple low shelf EQ on your speaker.
In my opinion, for all practical purposes, you can completely ignore any advice about setting up your speakers that you may find in your speaker’s manual.
So What DOES Matter?
The thing that doesn’t satisfy me about all of this is that I still don’t have a way of determining exactly where I should place my speakers.
If it doesn’t matter much where you place your speakers in relation to the the walls, then what does matter?
The simple answer is: It matters where you place the speakers in relation to your ear.
You see, there’s another surface, apart from the speaker membranes where reflections combine with the direct sound to cancel out or sum together. And that surface is your eardrum!
The timing of sound waves arriving here doesn’t just cause comb filters in the low end. It can mess with how you hear the entire frequency response and sound stage from your speaker.
In fact, the timing of sound waves here can have a huge impact on the stability, focus, width and depth of the stereo image. Our brains are incredibly sensitive to small differences in timing, direction, volume and timbre of those reflections.
But it’s not enough to simply set up your speakers in an equilateral triangle and be done with it.
It would be, if the speakers only shot sound waves directly at your ears. But they don’t.
In fact, your speakers send a pretty chaotic mishmash of frequencies in all directions, dependent on their dispersion character.
This energy then gets reflected, delayed, and potentially further filtered. It arrives back at your ear as an utterly destroyed version of its former self. And your poor, confused brain, incapable of telling any of it apart, jumbles it all together and tries to somehow makes sense of it.
Optimize Your Speaker Positions for Stereo Sound and “Body”
This kind of confusion can lead to a vague and ambiguous sound stage, lacking body and overemphasizing certain frequencies. That is exactly the opposite of what you want.
Of course, there is some combination of speaker position and reflection paths that minimizes both the effect of comb filters and this brain confusion.
If you’ve ever heard a room where this positioning has been optimized, you know just how exciting and pleasurable the experience is. I’ve often heard people say that it’s like working on good open-backed headphones. Everything snaps into focus. It feels like all the instruments are floating in space in front of you. You could just reach out and touch them.
But the problem is that your room has its own, very unique reflection pattern. So it’s literally impossible for any rule of thumb or general guideline to tell you where that exact, perfect speaker position is.
Short of hiring a professional acoustician to measure every last angle, nook and cranny of your room, the only way to do it is… Drum roll please…
By using your ears.
The speaker position that sounds the best to you IS the best in terms of distance and reflections.
To get the most of this method, you do need to know what you are listening for, and it helps to have a structured approach for listening to speaker placements to optimize your final speaker position.
Using your ears can tell you exactly at what distance you should place your speakers to minimize the effect of comb filters. It can help you optimize the combination of direct sound and reflections. It lets you find the spot for your speakers where your stereo image and sound stage end up being the best they possibly can be in your particular room.
Providing the exact details for how to do this with a minimum of time and second guessing deserves a post in and of it self. I call my method the “Phantom Speaker Test”, and if you’re ready to try this approach for yourself, I have a free step-by-step guide for you that walks you through the process.
When you have tried it, let me know in the comments below: Did you find the phantom center? How does it sound? And how close were you with your original speaker setup?
 Toole, F.E., 2008. Sound Reproduction: Loudspeakers and Rooms. Focal Press.
Alton Everest, F. and Pohlmann, K.C., 2009. Master Handbook of Acoustics. Mc Graw Hill.
Jesco Lohan is a platinum award winning mixing engineer and studio acoustician from Berlin. He recently started AcousticsInsider.com to teach busy music professionals acoustic treatment techniques that actually work, without all the voodoo. So they can stop chasing their tail and work fast, to truly rely on what they hear and the decisions they make.