There’s lots of talk about the best elevation for surround speakers in an immersive system, but are we missing something? Speaker groups don’t operate in isolation; they work together to create the immersive envelope. You can’t comprehensively discuss the proper elevation for one group of speakers without considering all of them. So, let’s do that, starting with the front and working our way around and above.
In the typical purpose-built home screening room (where movies are the priority), the LCR speaker acoustic centers are about 1/2 to maybe 5/8 up the screen, which places them more or less at the actors’ mouths. Thus, the LCR elevation depends on things like risers and sightlines, speaker crossover lobes, vertical array lobing, speaker-boundary interferences, and standing waves — all of which should be considered in the design. But let’s assume it all averages out to about 12 inches above seated ear height.
If music is a big influence on the room, then drop the acoustic centers down to around 6 inches above ear height to improve soundstaging. It never hurts to mention azimuth, and we all know the L/R speakers should be at about 22.5 degrees from front center, or maybe a little wider for the music soundstage.
The rule of thumb for Side speaker elevation is 15 degrees above ear height based on the center listener in the closest row. What’s magical about 15 degrees? It comes from the way dubbing stages and cinemas are set up, where practical demands of audience coverage necessitate that surrounds be significantly elevated. If they aren’t, the people close to one wall get rocked by those speakers and won’t hear the others at all. That’s not the effect sound mixers are going for, so the surround speakers are elevated in order to smooth out the experience for everyone. The same logic applies to the rooms we design for homes.
I’m going to stop and address two questions that you should be asking at this point. The first is, what about music surround? The second is, what about Dolby’s guidelines to put speakers at ear level? The answer to both questions is essentially the same.
Music surround mixes and Dolby’s guidelines are based on a single-listener-centric experience — audio enthusiasts setting up systems for themselves. Music surround mixes are not intended for a room full of people, and you cannot make them sound right in that environment. Likewise, the pretty little diagrams on Dolby’s website are not created for integrator-space multi-seat residential screening rooms — nor are the cinema guidelines. Our rooms are a hybrid between the single audio enthusiast and the cinema. Unfortunately, that market isn’t big enough to have guidelines or diagrams drawn up specifically for us. It’s assumed we’re professionals and can make the adaptations ourselves.
For Side azimuths, the typical 90 to 100 degrees at main row is fine. If you have two rows, it may or may not be beneficial to add a second pair 90 to 100 degrees from the second row. Three rows definitely need two pairs. Four rows need three pairs. If you have more than four rows, you’re probably not an integrator in a residential space reading this article!
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The Back speakers should also be 15 degrees up based on the back row. However, you must ensure both the Side and Back speakers are high enough to clear seat backs and heads — even if this requires you to elevate the speakers more than 15 degrees! Tilt them down so that the listeners are within the vertical pattern of the speaker and don’t lose treble or midrange from speaker beaming.
Back speaker azimuths can get kind of crazy, but — as Gary Rydstrom’s co-conspirator in starting all this mess with Back speakers in the first place — I can tell you that the typical 135–150 degrees is not far enough back. They need to be 160–165 degrees from front center. If you want to know more, I’ll be happy to give you the whole history of how it happened…offline.
Okay, retracing back to Wide. Elevation-wise, the acoustic center of the Wide speakers needs to be halfway between the LCR and Sides. Azimuth is 40–45 degrees, but not super important. Wide is kind of mess right now because of how it’s being remixed, but we won’t go there.
Finally, let’s talk about Top speakers. Here’s how the dubbing stages and cinemas are set up, as well as what mixers want to do with sound overhead: The Top speakers are arrayed in two lines about halfway between the Center and L/R (or about 1/3 of the way across the ceiling). The mixers’ number one objective is to provide a smooth pan from Center to the Back for flyovers. Objective number two is to create the general sensation that an ambient effect, like rain on a roof, is overhead.
When it comes to designing a home theater, the position of the Top speakers should accomplish these two things — regardless of specific azimuths and elevations.
Based on numerous examples of multi-seat rooms with the Side and Back speakers at 15 degrees elevation, I’m going to suggest departing from the diagrams in Dolby’s consumer website in the following way.
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Stick closer to the dubbing stage/cinema model by placing the Top Left speakers halfway between the Center and Left speaker and Top Right halfway between Center and Right. Place the first pair of Top speakers (T1) at about 60 degrees elevation based on the front/main row. If you are sitting in the front row, this means T1 will be in front of you, 30 degrees forward from directly overhead. In rooms that are 16 to 20 feet long, this is really all you need and provides seamless pans as well as a general sense of overhead. For a 20- to 30-foot room, add a second pair (T2) about 30 degrees behind the front/main row (mirror image T1). If the room is more than 30 feet long, a third pair may be added between T1 and T2, resulting in T1, T2, and T3.
Avoid the temptation to crowd three sets into a too-small room. The T2 pair can actually degrade the experience in rooms less than 30 feet by creating confusion and comb filters. Our ability to resolve spatial differences overhead is simply not acute enough to parse that many tightly clustered sound sources. The middle pair of Top speakers (T2) should never be directly overhead for the front/main row; it should be slightly in front of the main row. If this causes T1 and T2 to appear to merge together into a signal sound source, you don’t need T2 and should remove it. Simpler is sometimes better!
Chase Walton ([email protected]) contributed to this article.