Design & Best Practices: Part 3

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Moving on to Loudspeaker Aiming: Horizontal coverage of most cinema screen channel loudspeakers is about 90 degrees.

For a typical room a best practice is to aim all three screen channel loudspeakers so that they converge at a point about 2/3 into the seating area.

Front rows are usually well within the coverage angle as long as they are not too close to the screen.

This achieves the best coverage with good stereo imaging for the most seats possible.

Even with this aiming, a loudspeaker with a 90 degree horizontal coverage pattern will deliver a lot of energy to the side walls.

So you can see why it is so important to treat side walls with acoustic absorption.

Now let’s talk about the location and aiming of Surround speakers.

These are aimed across the room toward the farthest listener, and should be mounted high enough so that they’re out of reach,

but not so high that they don’t cover the seating directly below the loudspeaker.

I’m not going to bore you with the math of calculating loudspeaker height here. You can take a look at the handout.

It usually ends up between 8 and 12 feet from the floor depending on the width of the room.

In the smallest rooms, 8 feet keeps them out of reach.

In large rooms, you don’t want to go much higher than 12 feet, otherwise the listeners below will be too far off axis.

Also, loudspeakers that are too low reduce the size of the stereo “sweet spot” in the middle of the room.

Surround loudspeakers are normally installed in approximately the rear 2/3 of the room for 5.1 and 7.1 systems.

We want to avoid placing the front surround too close to the screen because of potential reflections off the screen and off the open floor area.

They should be fairly closely spaced – no more than 12 feet apart for the largest rooms. We recommend 8 or 10 foot spacing as a good target for average size rooms.

The purpose is to create a seamless sound field.

The loudspeakers should all be mounted roughly the same height from the floor, according to the slope of the seating,

and they’re are usually configured and wired in groups, or arrays, up to 4 in parallel, per amp channel.

Along the rear wall of the room above the last row of seats,

Surround loudspeakers should be mounted high enough so that they can’t easily be reached, at least 8 feet from the floor.

Lateral spacing should be approximately the same as along the side walls.

Due to the slope of the floor, rear wall surrounds usually need to be aimed downward more steeply than side wall surrounds.

QSC makes a special wall bracket that adds another 8 degrees of tilt just for this purpose.

The number of surround loudspeakers you’ll need in a room is highly dependent on the room dimensions.

The key factors are room length and width, and the spacing between loudspeakers.

There’s a formula that works pretty well and we’ve put it in the Downloads section. You’re welcome.

The exact location of Subwoofers is a little less critical because they are omnidirectional,

but typically they are located on the floor below the screen, with acoustically transparent draping to hide them from the audience.

They should be placed slightly off-center to avoid creating a “sound alley” and multiple cabinets should be clustered together

to take advantage of mutual coupling – which is additional low frequency energy caused by the loudspeakers being placed together,

without having to pay for additional amplifier power.

So it’s free. A gift from us to you.

Alright, let's take a break there and come back when you're ready.