The Basics of Surround Sound - Part 2

For anyone who has an interest in sound and post-production for film, TV, gaming, and music, one of the skill sets that you’ll definitely need to have is an understanding of discrete surround sound audio.

By discrete, I mean the use of a setup that works in a multi-speaker listening or mixing environment. This could include a 5.1, 7.1 and even up to a 9.1 Auro or Dolby Atmos configuration with added height speakers.

Most of the visual and gaming media have embraced multi-channel audio to such an extent that it’s become an integral part of the overall experience — and you’ll need the knowledge, skills, and tools to work in this environment.

The Room

The most logical starting point for upgrading to a surround environment is to step back and see how the extra speakers will integrate into your room. In my opinion, it’s best to get into the surround game is by starting with a basic 5.1 system. And before you begin moving things around, try envisioning where you will place your center and rear speakers.

For example: if your existing L/R speakers are resting on a desk, is there a place where you can put the center speaker without obstructing or being obstructed by your video and/or computer monitor? If you put your rear speakers on floor stands, will they constantly be in the way of foot traffic?

Personally, the way that I got around all of this was to hang my speakers from the ceiling (some speakers actually have rear screw-points that makes such mounting easy). My ceiling height is high enough that the center speaker rests above the video monitor and the rears are just above my head height, pointing slightly downwards towards the mix position. Obviously, every setup will be different. Take the time to think things through in a way that works best for you and your room.

The Speakers Front & Center

The next big consideration rests with your choice of speakers. Hopefully, you’re currently working with a set of L/R speakers that you like or are at least are used to. If not, this might be your chance to start fresh!

Let’s assume that you love your stereo pair and want to stay with them. It’s important to note that although you could start out with a different center speaker that’s close in sound and design to your existing L/R pair, however, it would be much better to use the same size and model across all of the L/C/R front speakers. This will improve imagery and to keep the overall sound consistent along the entire front soundfield.

Consistency in placement is also important. For example, if the L/R pair is placed higher up and the center speaker is laying flat under the video monitor, reflections and other considerations could easily color the imagery and sound balance between the L/R and the center speakers.

The Rear

Rear speaker choice and placement is a slightly different matter. Although they should be close in design and overall sound to your front speaker, it is possible to have a bit of variation. For example, if you have speakers with 8” bass drivers along your front and the same manufacturer has the same model with 6” drivers, this smaller speaker could be used in the rears without encountering too many problems. That said, if you can match the speakers all the way around as closely as possible, it’s always best.

Finally, I tend to favor placing the rear speakers in a 110° arc behind the mix position, with the high-frequency drivers being angled outwards. This will provide for the greatest degree of rear high-frequency localization. You might want to experiment to see if this works for you, as well.

The LFE and your Subwoofer

The LFE, or Low Frequency Effects channel, is the audio track that specifically handles all of the super deep, low end information ranging from 3-120 Hz. Typically this channel is sent to your subwoofer.

While the LFE — which is the ".1" in 5.1, 7.1, etc. — is “band limited” to below 120Hz, it’s a common misconception that this track is intended to act as the lone source of bass content to be sent to your subwoofer. It's not. It was originally designed to give an extra low-end "push," for extreme, sub-sonic, earth-shaking vibrations and effects in a theater during an earthquake, explosion, etc.

So use the LFE track to add extra support to sources such as a kick drum, bass, or synth track, but it’s never wise to rely on the LFE as inaccurate system setups (and even your own playback setup) can easily introduce low-end level problems into a mix.

Be warned, Murphy’s Law just loves to creep up into the LFE channel. Watch the levels of this track very carefully. Personally, I set the LFE levels at around -10dB relative to the overall levels, as having the LFE at full mix level can bring about a bass BOOM that could easily shatter your mix. Just remember, there are no rules, just guidelines, and experience is the best teacher.

The DAW

Unlike within stereo production, with regards to working in 5.1, 7.1, 9.1 and higher, all DAWs are definitely not created equal. Some DAWs will only work in stereo, while others can deal with surround but might offer up resistance when the going gets even slightly tough. A few, on the other hand, are very surround/immersive friendly in a way that can make your job much easier.

I won’t name names, but even a quick Google search into the multi-channel mix capabilities of a DAW will quickly tell you if it's a friend or foe during even the simplest surround mix. It’s always best to talk to your peers, read the literature and reviews, and then give your current DAW a try before you buy something new.

The Interface

As with your choice of DAW, not all audio interfaces are created equal when it comes to surround. You can completely rule out the use of a 2-channel interface and even most multi-channel interfaces as it’s likely that they will not provide a linked surround level control.

Without a single, ganged volume control that can adjust all of your surround output channels simultaneously, there will be no way to vary your overall monitor level without using a seperate surround monitor control — which can be even more costly than your interface. Many professional audio interfaces offer surround sound capabilities, including Universal Audio's Apollo X, with full surround sound support up to 7.1.

How to Setup your System

Lastly, as with a stereo speaker system, it’s important to make sure that all the speakers in a surround system are set to their proper reference levels at the listener’s position. This is done by generating pink noise in your DAW and playing it back at equal levels over each of your output channels. Obviously, it’s a good idea to save this special calibration session for use again at a later time.

Personally, I get my trusty tripod out, and place an SPL (sound pressure level) meter on the stand at the listener’s position and begin playing back the pink noise at levels around 80 to 85dB SPL. Then, while playing one track at a time, you can go about setting your output levels on each speaker (or on your interface, if it has provisions for individual surround speaker trims like the Apollo X audio interfaces) so that they’ll equally match on the SPL meter.

Setting up levels for the LFE differ from the other full-band speakers, in that the levels should be set to +4dB SPL above the other reference levels. Once all speaker levels have been calibrated, you can then get down to the process of mixing in surround.

Finally, I highly recommend The Recording Academy’s (the Grammy folks) in-depth guidelines on setting up a professional surround system. It’s not the easiest of reads, but you’ll certainly learn a lot from the best in the surround sound biz.

Make sure and stay tuned for Part III as we dive deeper into your surround sound system!