One of the most common complaints about ceiling loudspeakers we hear from the architecture and interior design world relates to the speaker position and density, especially in rooms like coffee shops and lecture theatres. Speakers always seem to be right out there, above the heads of people, right where they are the most conspicuous.
We understand that interior designers and architects would prefer that ceiling mounted loudspeakers don’t interrupt the symmetry of various fixtures and fittings on the visible ceiling. Unfortunately the lighting layout at coffee stores always gets the first shot at the ideal locations and the symmetrical layout, followed by HVAC diffusers, it always means we’re working around lights and diffusers for speaker layout. As a result we’ll take any remaining space and try to develop a speaker layout that provides uniform coverage at ear level (where it counts).
We often face grumbling because of the additional clutter of ceiling loudspeakers, especially in low ceiling spaces like cafeteria or hallways. And we often face questions about the density of speakers needed to achieve coverage at ear level. While the lighting is often laid out with its uniformity defined at the floor, our speaker layout has to be uniform at ear height (typically 42″ or 1060mm AFF for seated listeners). And then there’s the surprise speaker shuffle problem, where one of the other disciplines will shuffle the speaker layout to fit around some new addition like sprinkler heads. It isn’t uncommon to see nice uniform speaker layout accordioned into odd spacing, with a pair of speakers two ceiling tiles apart and then ten ceiling tiles to the next one.
Ceiling speakers, much like a coffee pot light generally have a conical coverage pattern, and as such have a limited coverage area. No matter how much an interior designer or architect might wish that a speaker can be coerced into changing it’s coverage pattern to be peanut shaped, or to shoot directly sideways, it pretty much covers the area “illuminated” by the cone of coverage directly underneath it.
As with any device featuring a conical coverage pattern, the higher you mount them, the larger the circle they will cover. And as you increase the area they cover, you must increase the wattage to maintain the same level per unit of area of coverage.
The image below is the same room with all three rows of speakers fired up. Note that the back row is still less unfirom than the middle row, in a perfect world, you might actually want to add a fifth speaker in the back row to decrease the centre-to-centre spacing, and increase the speaker density (of course you would do that with much grumbling from the interior designer or architect because it wouldn’t match the middle or front row).
In order to avoid that problem, a speaker would actually have to be fairly quiet close to it and get louder further away, and the laws of physics don’t work that way in our universe. But that type of speaker is an entirely different mythology to debunk. We’ll save that for another time.