Surround Sound Microphones

[David Seguin]

I was just wondering if you can use a surround sound mic with any recorder/camcorder. The reason I'm asking is because to my (very limited) knowledge, most cameras and recorders don't record in 6 channels, yet surround sound is "5.1".

Also, I wanted to know what your opinions are on surround sound mics. Are they worth using? I know they're far from necessary, but if the results are good then maybe I'll look into it a little more.

My setup is pretty basic. I usually just plug a shotgun mic directly into my camera, leaving one XLR input free, which is where I would plug the surround mic if I had one. Would that work? Assuming it would (which at this point I doubt), I'd be able to record dialog clearly with the shotgun and use the surround to pick up ambience and other effects in the scene.

Note: Most of this is hypothetical, considering my NLE setup wouldn't really allow me to monitor in surround sound anyway.

[Jon Fairhurst]

This would do the trick. It uses Dolby encoding to record the surround sound on two tracks:

PortaMic 5.1

I have no idea how this little guy sounds, but the larger, pro version has been used as the audience mic for broadcasting live events. I recall a story about the Grammys setting up for surround with lots of different mics, and they had horrible phasing issues. They replaced the whole audience mic setup with one Holophone. The NAB demo sounded great.

You wouldn't use this for dialog, but it would be a nice solution for a documentary shoot where you're in the middle of some action.

[John Willett]

To record surround you need at least 3 channels.

With the MSM (double-MS) method you use front and rear facing cardioids plus a sideways facing fig-8. You then matrix these three channels to 5.0 (or whatever) - NB: the .1 bit is the LFE channel (Low Frequency Effects) and is never recorded by a surround mic. , the .1 is *not* the bass information.

With a mic. such as the Soundfield (I am playing with the new SPS 200 at the moment) you need 4 channels and convert this to 5.0, 7.0, stereo or whatever in the DAW.

I would record on a separate recorder and use timecode to sync. with the camera.

I hope this helps.

[Brian P. Reynolds]

I have been involved is several Outside Broadcasts using the Holophone H2 mic with STUNNING results the output is 6 channels un-encoded.
Since then Holophone have developed a 2 channel encoded mic for use on small cameras being the PortaMic 5.1 or pro. It can be decoded for post production.
The production concepts and way of thinking need to change in surround sound as you need to be mindful of whats also behind you, In video production it may be better to record "wild atmos" in surround and underlay this with the normal mono / stereo Fx mic.

The PortaMic pro and a Zoom H4n might be an intersting combination for someone to try.....

[Jon Fairhurst]

> "In video production it may be better to record "wild atmos" in surround and underlay this with the normal mono / stereo Fx mic."

I tend to agree. For most of my stuff, the only thing I need live is dialog. Everything else can be added after the fact.

The one exception would be when shooting a doc in the middle of something acoustically interesting with a fairly wide lens. For instance, at a county fair, you might have a roller coaster to the left, a dart game in front, and a merry go-round on the right with people streaming past you. Being immersed in those sounds and having them tied to the action you see on the screen could be really compelling. On the other hand, stuff that doesn't need sync, like a waterfall sound, can be recorded at any time and panned as needed in post.

[David Seguin]

Very interesting to know. Thanks for the replies.

[Steve House]

Note that most Surround Sound is actually created in post. When surround is recorded in the field, it is the LF, RF, LR, and RR channels. The centre and sub channels are created later.

[Jon Fairhurst]

Very true. For movies, my understanding is as follows:

Dialog - center. Maybe you pan a voice that is off screen, but on-screen dialog is simply mono, center.

Music - LF & RF, panned wide. You might mix some reverberation to the rear channels, but that's it. It's panned wider than, say, a classical recording in order to make more space for the dialog.

Foley and sound effects - LF, RF, LR, RR. This surrounds the viewer in order to create an aural environment. Don't go too heavy on the rear channels to keep from being too obvious. You don't want to take the viewer out of the story.

Booms and rumbles - LFE. These special sounds go to the subwoofer channel.

As I understand it, a surround sound system will mix low frequencies from the other five channels into the subwoofer depending on the system. This is done on playback, rather than in the post production studio. The reason is that one system might have a set of full range speakers. Another system might have tiny satellite speakers that don't reproduce sounds below 200 Hz. The full range system doesn't need to mix anything extra to its subwoofer. The satellite system will send everything under 200 Hz to the sub. A third system might have a 100 Hz cutoff. There's no way to anticipate what the playback system needs when doing the studio mix.

This brings us back to the original question about recording surround live. It's only important when you are surrounded by an interesting environment of sounds that sync with the picture. The carnival is one example. Being in a sports stadium while doing "the wave" might be another. If you also have dialog, use an additional mono mic that is close to the subject. Music can be added later in stereo. But most of the time, the environmental sounds can be added in post from non-sync sounds.

[Steve House]

Audio that's in the surrounds is almost non-sync by definition, unless you put a screen in the back of he room and the viewers have eyes in the back of their heads. LOL It would be very rare that something you SEE in front of you would be HEARD behind you. Somethings might be sort of sync, like a shot on screen with a bullet impact behind, but even that can be put in in post and doesn't need to be recorded in the field.

[Jon Fairhurst]

Maybe it's semi-sync.

For instance you are looking at a train as it comes toward you. You don't turn your head (camera) as it passes by. The train sound continues behind you. It might "toot", but the timing of that sound doesn't really matter.

Or a bird flies overhead. You hear "caw!" behind you. The timing and placement have to be timed to create the illusion, but you don't have to sync it with the movement of the bird's beak.

So the semi-sync surround stuff is generally a continuation from motion that you saw in front of you - like when you walk through the carnival as you pass the roller coaster on your left and the carousel on your right.

[Steve House]

Yep ... a good example of field recorded surround is the movie "Australia" where Luhrman had the ambient winds etc recorded in surround to capture the emotion of the vast expanse.

[David Seguin]

All great info to know.

Here's another related question:

How is surround sound handled in post? Do you need a special sound card to handle it? Or can just about any pc handle it?
How would you set up LFEs? From what I've gathered, there's no specific channel for that, so would you just center it and let the viewer's system deal with it?

[Steve House]

Most of the better audio software (Audition, Nuendo, Vegas, etc) handles multiple channels easily but you need a sound card or audio interface that has at least 6 output channels as well as the necessary monitors to be able to listen to the mix. Don't know where you got the idea there's no specific channel for the LFE - a workstation set up for surround mixing has outputs for all 6 channels and the software's mixer is set up to utilize all 6. Outputs 1 thru 6 are usually assigned in order as: Lf, Rf, C, LFE, Ls, Rs. In a stereo mix you can pan a mono source track to either left or right in whatever proportion you like; a surround DAW's mixer expands on that to allow you to pan source tracks from the mix into any of the 6 output channels as desired. The monitor system or the listener's playback system's bass management may also re-route low bass from the other channels into the subwoofer but tracks panned into the LFE channel go directly there.

[David Seguin]

Originally Posted by Steve House

Don't know where you got the idea there's no specific channel for the LFE - a workstation set up for surround mixing has outputs for all 6 channels and the software's mixer is set up to utilize all 6.

Oops lol. It's what I understood from Jon's comment v v v

Originally Posted by Jon Fairhurst

As I understand it, a surround sound system will mix low frequencies from the other five channels into the subwoofer depending on the system. This is done on playback, rather than in the post production studio. The reason is that one system might have a set of full range speakers. Another system might have tiny satellite speakers that don't reproduce sounds below 200 Hz. The full range system doesn't need to mix anything extra to its subwoofer. The satellite system will send everything under 200 Hz to the sub. A third system might have a 100 Hz cutoff. There's no way to anticipate what the playback system needs when doing the studio mix.

[David W. Jones]

Surround sound is one of those critters that has never really taken a forefront like I thought it would.
At least in my market. I added surround mixing to my studio many years back, and have since only done a handful of projects. Most of the local TV stations haven't a clue when it comes to passing the signal, but then again they can't even figure out embedded anamorphic flags. And with budgets getting smaller and smaller, most indie projects or docs I remix don't want to pop for the added expense of creating a separate 5.1 mix, let alone spend the proper amount of time to make what they have sound airable.