The Basics of Surround Sound - Part 3

When talking about sound source placement in the recording and mixing of immersive audio using traditional headphones, 5.1, 7.1 or 9.1, I feel the first rule that applies is, there are no rules.

For traditional recording and mixing, there are tried-and-true guidelines that have proven successful for decades. However, when it comes to placing sources in immersive audio, there aren’t even any guidelines. Actually, there is one guideline that applies to mixing immersive audio for video or film — place the dialog track in the center speaker — but this isn’t even a total hard and fast rule.

Panning and Placement in Surround

There are myriad ways that sounds can be placed into an immersive soundscape. One of the most common is used in the recording of classical music, the "Decca Tree." Typically placed over the conductor, this three-mic setup spreads the soundfield across the front L/C/R speakers, while additional room mics can be sent to the rear speakers. This setup will often give us a natural “you are there” room sound that many classical buffs have come to expect.

Film scoring will often combine the above classical approach with a semi-distant technique that makes use of additional close instrument pickup mics for added presence that can be mixed in with the main mic tree.

Likewise, creating an immersive mix for music is open to whatever is called for by the project or the desires of the producer, artist, and/or engineer.

For example, a rock concert immersive mix could follow the classical "Decca Tree" model, in that the songs will be mixed across the front speakers in almost a standard stereo style, while room sound and the audience ambience will be placed in the rear — nice and simple.

Using a bolder approach, a music-only mix might place the various channels within a session across any or all of the speakers in the surround field. Here, you’re open to go nuts, by placing sounds in their traditional spots, or you can experiment your heart out. Remember, there are absolutely no rules.

I approach my mixes from a different angle altogether. Throughout my entire career, I’ve always recorded almost all of my session tracks in stereo. And by layering up lots of drums, percussion, bass, and groove tracks, I can route the stereo tracks across the front, sides, rear, and center speakers to create a “You’re-in-the-middle-of-the-music” sound that immerses you in the mix in an open, engaging way.

The crazy part is that I use no panning, except for the occasional stereo autopanner. The sheer number of separate instruments placed around the entire soundfield provides all the movement I need.

Using Delay in Immersive Mixing

Delay in surround and immersive mixing can be a lot of fun, allowing for experimentation and musical interaction that has to be experienced to be believed. For example in one of my mixes, I placed a stereo kick in the rear speakers, while a delayed reverb of the track was then routed to the front center speaker in a “call and response” fashion that was truly impressive. Put another way, the delay of a mono or stereo track in a mix can be panned to alternate speaker sets, i.e. tracks coming from the front L/R can be delayed in the rear, creating a larger and interesting sense of space.

Using Reverb in Immersive Mixing

Since immersive audio is all about creating a sense of space, it makes sense that one or more reverbs will help play a part in creating size and depth to a mix. The use of multiple stereo reverbs which are routed to both the front and rear speakers can add contrasting space to a mix. Surround reverbs can also be used to add a sense of cohesive “glue” to vocals, strings or other instrument groupings.

Re-amping in Immersive Mixing

Re-amping sources with immersive in mind can be a lot of fun over the standard one or two mic approach. For example, when reamping an electric guitar rig at a later date within an overdub setting, you might place one or two mics at a close distance to the guitar cabinet in the usual way — but you can also place an additional stereo X/Y pair at a distance to get a slightly fuller sound.

You might also put a room pair further out into the room in a stereo Blumlein (cross figure-of-eight) pattern. Once re-amped, these various distance combinations can be combined into the mix to add a greater sense of space, both in the stereo and the surround mixes. Alternately, these room mics can be panned to the rear speakers of an immersive mix.

As you can see, mixing and recording with immersive in mind is far from boring and can give you an extra production edge by taking things just a little bit further, making your productions shine.