Loudspeaker - In Room Placement and an Optimized Position
Step 1 – Placement
This involves establishing the optimum distance of the speaker's position from the front and side wall as well the listening position and center of the audio system. The process I use to establish that position involves careful movement and precise positional measurement. Once I have achieved the most linear and robust low-frequency response, this becomes our Zero Point or point of departure for Step 2. Such precise alignment requires levels with digital readouts in degrees of angular error and self-leveling lasers to assess the relative position in space. Those tools will be fundamental to the process of optimization – by allowing me to adjust each speaker precisely, relative to that Zero Point.
The Concept Of Noise
I’ve already spoken about the concept of assessing audio performance in terms of intrusive or additive noise – and improving system performance by eliminating that noise. It is an instrumental concept when it comes to speaker placement. Bass hump in your room? That’s noise. Slap echo or early reflections? Noise. But how does that help us position loudspeakers?
The acoustic pattern within a room is defined by a grid of pressure peaks and troughs that vary in height/depth – and those peaks and troughs are surprisingly close together. They are why the bass output of a speaker changes when we move it; we are balancing it against a peak or trough in the room’s acoustic grid to minimize excess noise. It’s also why there is often more than one place that a speaker will work – and why we can often achieve remarkable performance even from an unpromising starting point.
Step 2 – Optimizatization
But it’s not just the room’s acoustics that operates on a grid principle. The sound dispersion characteristics of each loudspeaker can also be put into a three-dimensional grid extending from each of its drivers. Visualizing this grid is enormously helpful in understanding how and why a speaker sounds the way it does and what you need to do to correct it. Try to imagine the three-dimensional grid as the sound suddenly freezing, becoming solid and visible. Each speaker driver would have a differently sized and shaped grid, depending on the frequencies being reproduced. A tweeter would have a tightly spaced grid of tiny cubes representing the short-wavelength high frequencies. The midrange driver’s grid would be made from somewhat larger cubes, and the grid generated by the woofer would, of course, be composed of large cubes representing the long-wavelength low frequencies. Each grid would be shaped by its driver’s dispersion. Using this visual model, a designer’s goal should be to have those grids coincide perfectly at the listening position. The perfectly superimposed boundaries represent a perfectly neutral and phase-coherent speaker.
Of course, things are never, ever that simple. Those driver grids will never be perfectly matched or regular. They might be distorted by non-linearities in the drivers or suffer interference from room acoustics. Nor will the drivers and crossovers in a “pair” of speakers be perfectly matched. But my job is to align those grids as carefully and accurately as possible by moving the speakers forwards and backward, raising them, and tilting them sideways or forwards and backward. This works because the different drivers are at different heights on the baffle, so adjusting the speaker angle at its base affects each driver slightly differently. With practice, you get to recognize the sonic symptoms (congestion, thinning, holes in the soundstage, etc.) and how to move the speaker to compensate. And because the tools I use map those shifts precisely, they are always repeatable.
I’ve described a classic three-way dynamic speaker, but the basic principle and approach will work for any speaker. Di-poles might drive the room differently, but visualizing that process is immensely useful in positioning them for optimum performance. The same is true of sub-woofers – or any other kind of loudspeaker. Conceptualizing the problem makes solving it possible: that and a lot of tools and a heap of experience.
It is a long and exacting process, but the results are remarkable. Your speakers might not end up placed exactly symmetrical or stood at the same angle – but they’ll never have sounded so good.