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The Main Event: I'm Surrounded!
Posted Jul 26, 2007 Print Version     Page 1of 1
  

I’m not a musician, or an audio engineer, or even a dedicated audiophile. Like most wedding videographers, I always try to capture clean, clear audio, but I’ve never cared if it was in mono or stereo, let alone surround. So why did I recently spend time and money on a major studio upgrade to surround sound? Two letters: HD. Up until now, my typical customer watched her video on a 27" television with built-in speakers. But more and more people are buying big-screen 16:9 displays and home theater audio packages to go with them. So my typical client is soon going to be watching my productions in widescreen HDTV with Dolby 5.1 or better audio. She’s going to expect the improved video and audio experience that they get when they play Hollywood movies on her home theater.


I started by doing the usual thing: I went shopping. After browsing through the catalogs and eBay listings, I came to the realization that I didn’t even know what most of the product descriptions were talking about! So the first thing I got wasn’t gear, but information. I downloaded some guidelines from Dolby about setting up a surround studio. A friend suggested the TweakHeadz Lab, and it was very helpful. I also ordered a very basic book, Jeffrey P. Fisher’s Instant Surround Sound (CMP Books). Soon the mists began to clear and I felt more confident in looking for equipment.

Caveat: I’m going to tell you what I bought, but these components are not the only (or necessarily the best) choices. They’re just one solution to the problem. I purchased an M-Audio Delta 1010LT sound card and a set of M-Audio LX-4 self-powered speakers. These are a great value new, but I bought mine on eBay and saved even more. The speakers were especially neat . . . all five of the satellites (left, center, right, right rear, and left rear) are identical two-way bookshelf units. They’re connected to the subwoofer, which contains a 50 W integrated amplifier. Your alternative is to get a Dolby 5.1-capable amplifier, and connect all of your speakers to it.

The next step was to tear apart the old studio and re-create it with an eye toward audio mixing in 5.1 surround. I re-oriented my editing desk so the main speakers would fire down the room’s long axis. Next, I placed the speakers as recommended by my helpful sources, trying to keep them all at ear level and an equal distance from the listening/editing position. One book recommended that the front speakers be placed 4' or more from the wall, to prevent wall-speaker interaction, but I didn’t want to give up that much working space for the sake of audio purity. The front speakers are on cantilevered mounts about 4" from the wall, with acoustic foam behind them.

I used a trick recommended by Fisher to find the "first reflection" surfaces in the room using a hand mirror, and treated those areas with absorbent material. (A surround-sound room, unlike a stereo mixing room, should be acoustically "dead." The ambience is produced by the extra speakers, rather than reflections.) Next, I calibrated the speakers using an inexpensive sound pressure level (SPL) meter from Radio Shack. This calibration procedure is analogous to calibrating your video monitor with color bars, and assures that you’ll be hearing a correctly balanced audio mix. You can find the detailed procedure in Fisher’s book; the short version is just to put the meter at your listening position. Play a test tone through each speaker in turn, and adjust the volume to get an equal SPL reading from each speaker.


figure 1The Delta 1010LT sound card has lots of inputs and a software version of an audio mixer, so I decided to retire my Mackie 1202 mixer and my audio patch bay and let the computer take on that function. The software can also handle equalizing and compression, so I removed those hardware components as well. I’ll admit that actual knobs are more convenient than mouse-controlled software sliders, but I was willing to trade off a little convenience for a much-reduced equipment inventory.

My entire library of buyout music fits onto my computer’s hard drive, so I also got rid of the CD player. The new studio configuration is much simpler than the old version; even considering the three additional speakers, I removed a lot of hardware and cabling. The project was surprisingly inexpensive; by offsetting the new gear’s cost with the sale of equipment I no longer needed, I kept the total well under $1,000.

I did run into a couple of unexpected "gotchas." These were related to using the system for listening to audio, as opposed to editing audio. First, the 1010LT doesn’t have a headphone jack. If you like to use phones occasionally for privacy, you might want to pick a different solution. Second, an awful lot of music isn’t encoded with surround sound. Unlike a lot of home audio gear, the 1010LT doesn’t have a "pseudo- surround" mode that will let a stereo track play from all the speakers; stereo audio plays just from the left and right (and the subwoofer). If you like to listen to music while you work on the computer, you might want to use a different approach. The less expensive Sound Blaster Audigy sound cards allow you to do these things, but don’t have the excellent professional audio connectors or specs of the M-Audio card.

For capturing audio at an event, you can use several microphones set up at different locations, or a cluster of microphones at one location, catching the sound coming in from different directions. But if you don’t want to bother with placing five or six microphones at your shoot, Voxengo offers Stereo Touch, a free virtual studio technology plugin that can take a mono source and widen it into a stereo image. This is wonderful for creating a surround "feel" from a single mono mic placed to capture general crowd noise and room ambience. Thanks to Mark Foley of VideoUniversity for this tip! Your audio sources will be the primary vocals (e.g., the vows); ambient sound either captured with a single mic and expanded with Stereo Touch; or from several independent mics and background music tracks. I like the buyout music from Digital Juice’s StackTraxx library. The advantage of this material is that it’s presented as individual instrument tracks, which the editor can mix as desired. This gives a lot more flexibility than using a stereo mix as the music source. A tool like the newly surround-capable Soundtrack Pro may also let you direct different instruments to different speakers, but I’m a Windows editor and haven’t experimented with it yet.

Capture all the audio and put it on the timeline of your audio editor. Each track is then positioned between the left/right speakers, and also between the front/rear speakers. Mixing in surround is actually easier than mixing in stereo, because the sound field becomes a two-dimensional plane instead of a line between the left and right speakers. This gives you more spatial "room" to place sounds into. Once you get all the speakers going, the overall volume goes up fast, so decrease it as needed. Next, each track is adjusted for EQ (frequency response). For example, you might want to decrease the audio content of a guitar track in the mid-range to leave more room for a vocal part to be clearly heard. Tracks can also have various effects applied, such as reverb, chorus (making one instrument sound like several), or noise reduction. Audio mixing is analogous to creating a multi-layered visual image with a graphics program like Photoshop. You want to end up with a harmonious and pleasing composition in either case . . . it’s just that one program produces results for the eye, and the other for the ear.

The main audio (for example, the vows or the toasts) is still mono. It’s heavily weighted to play in the center, or "dialogue" speaker. It’s the ancillary audio and the music backgrounds that are manipulated to create the surround effect. Once you’ve created a mix that pleases you, it has to be encoded to an AC3 or DTS sound file. This process is to audio what rendering is to video. The audio data is encoded so that it will play back in mono or stereo, but when played on a surround-sound system, it will be decoded and the proper sounds will be sent to each of the speakers in the system. The software handles that, but be sure to check it by playing the finished mix in a surround system, a stereo system, and a mono system. You don’t want to make the mistake that I’ve seen several of the cable networks make—mixing audio that’s optimized for surround playback but has dialogue so low it’s hard to hear over the background music when you’re listening on a stereo system!

I’m happy with where these audio upgrades have taken me; here’s hoping you, too, will get surrounded soon!

Resources Mentioned

Voxengo Stereo Touch
http://www.voxengo.com/downloads/?highlight=stereotouch

Instant Surround Sound, Jeffrey P. Fisher. 2005, CMP Books, San Francisco
http://www.vasst.com or http://www.amazon.com

StackTraxx. Digital Juice
http://www.digitaljuice.com

M-Audio soundcards and speakers
http://www.m-audio.com

TweakHeadz
http://www.tweakheadz.com/surround_sound_studio.htm

Dolby Surround Sound Manual
http://www.dolby.com/assets/pdf/tech_library/44_SuroundMixing.pdf

Radio Shack Sound Pressure Level meter
http://www.radioshack.com/product/index.jsp?productId=2103667&cp=&sr=1&origkw=SPL+meter&kw=spl+meter&parentPage=search

Learn more about the companies mentioned in this article in the EventDV Videographer's Guide:
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