Anthony Grimani (firstname.lastname@example.org) is president of Performance Media Industries, with offices in Novato and San Anselmo, CA. You’ve probably heard all about Dolby Atmos, the new immersive audio format hitting the consumer market. Everyone is jumping on board, from big box retailers to custom high-end outfits. Atmos, in its cinematic form, supports a dauntingly large number of channels; how do you integrate that in the limited confines of consumer spaces?
First off, you’re going to see some HTiB solutions and speaker add-on modules. These are great for consumers and enthusiasts, but not for your clients. You’re going to be dealing with a few more speakers and amplifiers. How many more? At this point, I would consider two wide speakers and two ceiling speakers the minimum for a high-end Atmos installation. This would be called a “9.1.2” configuration using the current nomenclature. To be on the safe side, you should pre-wire for at least two more ceiling speakers. Audible improvement will decrease incrementally as you add more speakers, so don’t go overboard just yet.
Wide speakers, placed at about 60 degrees from center, are arguably more important than the heavily hyped ceiling element. One of the most challenging areas of the sound field to reproduce correctly is the transition from the screen speakers to the sidewall surrounds. All too often, pans jump abruptly from one to the other instead of moving smoothly. Wide speakers address this by adding a physical sound source between the two points rather than relying entirely on phantom imaging. Ceiling speakers (particularly toward the front of the room) perform a similar function in the vertical plane. They create smooth pans from the screen speakers over the audience and eventually to the back wall of surrounds. Thus far, vertical flyovers in mixes are less common than the ubiquitous off-screen side pans; hence the reason I would prioritize width speakers rather than ceiling speakers.
Dolby recommends this basic set-up when using mounted speakers on the ceiling. When using in-ceiling speakers, however, the recommendation places those speakers closer together in the middle of the ceiling. The jury is still out on the exact performance requirements for wide and ceiling speakers, but we know enough to get started. Because the wide speakers will be working closely with the screen speakers, it’s important that they have similar sonic characteristics and amplifier power. I’ll stop short of saying you should make all five speakers and amps identical, but your best bet is to do just that. At the very least, wides should be higher performance with higher directivity than the surrounds. Ceiling speakers typically will receive less energy from the mix and can be similar to the surrounds in performance and amplifier power. Assuming that you’re using bass management (and shame on you if you aren’t), it’s not necessary to use giant speakers. The subwoofers will take care of the heavy bass lifting, allowing even relatively small ceiling speakers to play plenty loud.
As with any speaker, placement, coverage, and aiming are critical. Wides should go at an angle that is roughly midway between the left or right speaker and the first surround speaker on the side wall. In most rooms, this will be about +/- 55-60 degrees from front center. If you’re dealing with a narrow room, be careful that this doesn’t put the wides excessively close to the seats. Remember, you don’t want to blast people in the face. Most screen speakers have wide horizontal dispersion, but it never hurts to confirm they are wide enough to cover the entire audience side to side from a closer distance. It should be self-evident by this point, but you must aim the wides at the audience like a screen speaker. Don’t just sink them flush in the wall to fire across the room at each other. This would put the entire audience at an extreme off-axis angle with poor frequency response and spray sound in parts of the room it’s not needed.
The first pair of ceiling speakers should go midway along the lines between the primary listening position and the L/R screen speakers–perhaps slightly closer together. If you opt for a second pair, they should go over the audience the same distance apart as the first pair. The ceiling speakers must also cover the entire audience and avoid spraying sound unnecessarily into places no one is sitting. It might be possible to get away with traditional “round” in-ceiling speakers, as long as the woofer and tweeter element can both be angled significantly to fire the audience area. However, I recommend angled-baffle in-ceiling speakers that typically offer superior dispersion control and aiming capabilities.
Chase Walton contributed to this column.