Chapter 27
Advanced Location Sound
This chapter summarizes some of the sound equipment, skills, and approaches that advanced productions need. You may want to review the basic information first in Chapter 11, Location Sound. Fortunately, there is now a great deal of expert advice posted on the Internet, and you’ll find some links and recommen dations at the end of this chapter. Sound equipment evolves less rapidly than cameras, so I’ve also listed some industry favorites in the discussions below.
Budget films often take less trouble recording sound than picture. Difficult or impossible to rectify in postproduction, this can disable otherwise good work.
Planning sound coverage poses a number of questions:
- Will you use the camcorder to record sound or a separate digital recorder?
- What kind of clapper board will you use if you are shooting double system (meaning a camera and sound recorder that are separate)?
- How many types of sound setup can you predict and how will you mike each different situation?
- How many channels of sound will you need to record?
- How many channels does your camera offer, and will you have to incorporate a multiple-channel mixer?
- If you plan to use radio mikes, should you bring wired mikes as backup?
- Should you rent or buy sound equipment?
FIGURE 27-1A Workflow diagram for single system. The camcorder records picture and sound together on DV cassette, P2 flash memory, or hard drive. Not shown is how the edited computer output becomes a DVD or film copy.
Shooting Single or Double System
When you shoot single system—that is, with the camcorder recording picture and sound—you have a common though clumsy setup that is hazardous for grab shooting because the camcorder and fishpole operator are linked by cables (Figure 27-1A). Shooting double system means using a separate audio recorder so sound and camera operate unattached (Figure 27-1B). This means that you can:
- Move together and separately at will.
- Record better sound than most camcorders.
- Get easier and more representative headphone monitoring.
- Shoot wild tracks as you need them.
FIGURE 27-1B Workflow diagram for double system, where an audio recorder handles sound separately.
But:
- You’ll need one or two extra crew members—to operate more elaborate equipment and keep records. Somebody must log sound and camera media, or bringing them together in postproduction will become a nightmare.
- Sound and picture must be synchronized for each take in postproduction, which is more work but not difficult—providing there are consistent sync markers and accurate logs.
- Marking each take with a clapper board makes your operation more visible.
- Recorder and camera inevitably drift out of sync. Creeping sync becomes apparent once they are more than 2 frames apart, which means only 1/15th of a second.
Depending on the level of your equipment, sound and picture may drift out of sync in the computer. Creeping sync may show up after 5 minutes of running time or not for an hour or two. Only tests can show whether you’re in luck. Shoot a 30-minute take with a clapper at the front and the end, sync sound and picture, then see how far the clappers are apart by the end of the half hour.
Using the Camcorder to Record Sound
Give yourself a shock and read Dan Brockett’s review of consumer camcorders’ sound (Internet address at end of chapter). Expect to encounter:
- Flimsy input sockets
- Inaccessible controls for changing input level while shooting
- Poor signal-to-noise ratio
- Ineradicable system hiss
- Occasional hum or buzzing especially when using direct AC (alternating current) power
- Input metering that is indefinite or misleading
- “Hunting” for level when set to automatic level and mike input is low
- Headphone output underpowered, auto level, or poor quality
Though most audience members will think the recording quality is fine, documentary often operates in marginal situations where substandard sound can tip the balance into unintelligibility. A documentary about music would have to be shot very, very carefully.
Safety backup: If you are using a single monophonic mike feeding into a two-channel camcorder, use a “Y” connector to feed its input into both channels. Adjust one channel to peak at – 6 dB and the other to peak several decibels lower. Should your main channel overload, you have a second chance in postproduction.
The largest drawback to shooting single system is that the camera operator, not the recordist, must usually monitor sound levels.
Sound Codecs
Digital sound recording also uses codecs and varying sampling rates. Sampling refers to the refresh rate the system uses as it draws sound waveforms. For sound fidelity set your sound sampling rate to 48k or above (48,000 waveform redraws per second) rather than the slower 32k. Stay consistent throughout your shoot because some editing software won’t accept mixed sample rates.
Location Recorders and Mixers
Using a separate recorder puts the whole job in a sound specialist’s hands, where it belongs. Digital audio, like video, can either record full information—which takes up a lot of hard disk or memory card space—or use a codec (compression/decompression, or coder/decoder, software) to condense the signal into less recording space. Your postproduction software must be able to accept the range of codecs—the most familiar being MP3—in which original and library sound are recorded. You will find an article comparing the different codecs and the operating systems that handle them at http://en.wikipedia.org/wiki/Comparison_of_audio_codecs.
Recorders
For reliability and high-quality recording, the long-established Nagra range is the classic (Figure 27-2; www.nagraaudio.com). Lower budget productions might use the feature-crammed four-track Sound Devices 744T recorder, which records onto a hard disk or flash card and sells for around $ 4000 (Figure 27-3; www.sounddevices.com/products/744t.htm). Or they might even consider the highly capable stereo TASCAM® HD-P2 (Figure 27-4; www.tascam.com) for about $1100; this records to flash cards and locks to external time-code for inter-machine syncing.
FIGURE 27-2 The Nagra® D II four-track digital recorder. Tough and reliable, Nagra equipment has long been the industry standard. (Photo courtesy of Nagra, a Kudelski Group Company.)
Robert Altman’s pioneering sound recordist built a location sound recorder capable of recording 16 radio microphones simultaneously to eliminate the rigmarole of following individuals with mikes while shooting. Today you could use a multi-track hard drive recorder intended for music recording such as the Korg® D8888 (Figure 27-5). It has eight XLR inputs, mixing and equalization, and a great deal more. For multi-mike setups (a music or theater production, say) you can handle up to eight mono mikes or four stereo and delay creating an optimal master track later. Multi-track recorders, however, are power hungry and usually require AC power from a wall outlet.
Miniature or inexpensive equipment may record fabulous sound but won’t be rugged enough to survive a documentary’s punishing use.
Zaxcom Deva portable state-of-the-art recorders combine 10-track location mixers and recorders and pack many track hours of uncompressed recording into a tough and hermetically sealed hard disk (Figure 27-6; www.zaxcom.com). The 10-second sound buffer is particularly useful for spontaneous shooting, since you always know on startup that the previous 10 seconds come with the
FIGURE 27-3 Four sides of the feature-packed Sound Devices 744T four-track audio recorder. (Photo courtesy of Sound Devices, LLC.)
FIGURE 27-4 TASCAM® HD-P2, a stereo recorder that locks to external timecode and writes to flash memory. (Photo courtesy of TASCAM.)
FIGURE 27-5 The Korg® D888 has eight tracks of input and mixing and up to eight tracks out. It records to a hard drive or makes direct data transfer to a computer. (Photo courtesy of Korg USA, Inc.)
FIGURE 27-6 The Zaxcom Deva V is a 10-track recorder using a hard disk, yet is light enough to sling over your shoulder. (Photo courtesy of Zaxcom, Inc.)
recording. The Deva creates DVD backup copies, plugs directly into a computer, and downloads rapidly in the cutting room. With no accessible moving parts, the machine is sealed and immune from grit and dust, as well as extremes of temperature and humidity.
Mixers
FIGURE 27-7 Excellence on a budget—the Mackie® 1402-VLZ3 mixer for 10 microphone/line inputs and two-channel output. (Photo courtesy of LOUD Technologies, Inc.)
If you want to combine and balance several mike inputs, you’ll need a location mixer, because consumer or prosumer camcorders usually have no more than two sound channels. Choose a mixer you can sling over your shoulder rather than one that must lie flat on a table. Professional Sound Corporation (PSC) makes excellent four- and eight-channel portable mixers, as do Wendt (www.wendtinc.net/index.htm) and Shure (www.shure.com/ProAudio/index.htm). Mackie’s mixers are favored by music and film productions (Figure 27-7;www.mackie.com). Sign Video’s ENG-44 is a modest and serviceable battery-powered portable mixer with four inputs and two outputs (Figure 27-8; www.signvideo.com/fpamxr.htm). Be aware that the more sound equipment you cobble together, the less mobile you become.
FIGURE 27-8 Basic ENG-44 battery-powered four-input, two-channel output location mixer. (Photo courtesy of Sign Video, Ltd.)
EQ and Rolloff
It is generally not a good idea to adjust equalization (EQ) as you record. You may however “roll off” (reduce) the excessive bass of traffic, since this can mis-register in the level meter and lead to distortion. Most microphones have low-frequency attenuator switches for this purpose; otherwise, record “flat” (all frequencies equally) and defer EQ to the postproduction stage.
Volume Unit (VU) Meters
On camcorders and mixers, most VU meters are averaging meters; that is, they display average sound level and not peaks, where distortion sets in. Your mixer may have red LEDs that warn of peaking.
Mixer and Camcorder Levels Setup
Use the mixer’s inbuilt tone-generator to set a saturation recording level of 0 dB on its VU meter. Feed the mixer output signal into the camcorder’s line level input (if it has one, or into the kind of input adapter box pictured in Chapter 11). Manually adjust the camcorder’s manual input levels (if you are setting up multiple channels) to also register a 0-dB reading. Record a minute of tone on tape, then check the tape with your editing program’s playback to verify that saturation recording is indeed 0 dB. If it’s off, lower the camera input until 0 db, and the mixer VU meter will handle a peak of any frequency without distorting.
Peak Tests
In mike recording tests, adjust mixer input levels so normal speech registers at −6 dB and peaks don’t stray into the red area. Using editing software, test tracks to check that levels and speech quality hold good. Experiment with deliberate overloads (peaking beyond 0 dB) to discover where audible distortion sets in and which frequencies seem most vulnerable. If necessary, ride gain during recording to keep from peaking into the red. This is difficult or impossible with camcorder-only recording.
Digital sound compared with its analog predecessor is very unforgiving, and you’ll need to learn from experimenting how to record within safe audio limits.
Multiple Microphones
If you keep all mixer channels equally open as you cover several people with several mikes, their ambiences add together to create a dull roar. To minimize this, hold every channel low when nobody is using it, and raise and lower each speaker individually. If, however, each mike records into its own channel of a multichannel recorder, you can record all at full level, then mix them later as needed.
Phasing
Multiple mikes feeding into a common recording channel can create phasing. You can recognize this phenomenon when the sound level pulses instead of holding steady. It occurs when further and nearer mikes pick up the same source, but in different phase relationships, and one periodically cancels out the other.
Recording Stereo
Unless you have studied the engineering parameters to stereo or 5.1 recording, don’t even attempt setting up multiple mikes. There’s even one deadly setup in which one channel cancels out the other when stereo is reduced to mono!
Phantom Power
If a mike mysteriously refuses to work, suspect phantom power problems (see Chapter 11, Location Sound).
Smart Slate
A smart slate is a clapper board containing a crystal-controlled timecode display (Figure 27-9). The numbers move when the bar is opened and freeze when the clapper bar is closed. For double-system shooting, this makes syncing sound to its timecoded picture easy. Camera and recorder must be compatible with the smart slate, and their operators must “jam” (synchronize) the timecode generators every morning, as they drift apart over a period of time. Carry a traditional clapper board if you fear electronic gadgets may break down.
Sound Monitoring
Good headphone isolation from the surrounding world is a must (Figure 27-10). Widely used professional phones are the Sony® MDR-7506 or MDRV-600 and
FIGURE 27-9 The Denecke smart slate electronic clapper board. The timecode numbers are in hours, minutes, seconds, and frames. (Photo courtesy of Denecke, Inc.)
FIGURE 27-10 Judging sound depends on headphones that isolate you from surrounding ambience.
FIGURE 27-11 Sennheiser® HD25 headphones are a location recordist’s favorite. (Photo courtesy of Sennheiser Electronic Corp.)
Sennheiser® HD-25 (Figure 27-11). Be aware that any camcorder headphone output that has inadequate level or passes through a compressor circuit will give a false impression of the recording dynamics. Compare what you hear on location with that during playback in the editing suite.
Monitor all recording all the time using professional, ear-enclosing head phones that isolate you from the surrounding world (see Figure 27-10).
Microphone Placement
Your choice of a boom or fishpole mount for the microphone is between aluminum and carbon fiber, the latter being lighter, which can mean a lot to its handler. A Gitzo ™ G1553 is inexpensive and extends to 11 feet. Expect to pay more for the convenience of having the cable pass through the pole’s interior. Whenever lighting and composition allow, mike from above. It gives a nice sense of changing sound perspectives, and speech level will be high in relation to the sound effects of body, hand, and foot movements. You can also mike from the sides of frame or from below. In the latter case, body movements can be disturbingly loud in relation to speech.
Microphone Types
Most documentary sound is shot using cardioid and hypercardioid mikes, as well as lavalier omnidirectional body mikes. Each has different pickup patterns that are related to how much each accepts or inhibits sound coming from off the mike’s axis. The cardioid pickup pattern gets its name from its heart-like shape.
Shotgun
Microphones have different constructions and sensitivities, but none actually reaches farther, as some people imagine. The hypercardioid or shotgun is ultradirectional and thus discriminates most strongly against off-axis sound. Named for their rifle appearance, shotguns like the Neumann KMR-82i or the Sennheiser® MKH-70 (an industry favorite) use interference tube serrations to suppress off-axis sound. Use this type of mike when you must favor a sound source over others competing from other axes, such as a speaker on a crowded street. The polar pattern (Figure 27-12) for the Sennheiser MKH-70 reveals that its off-axis discrimination varies according to frequency, a feature that is in fact common to all mikes.
Sorry, but there’s no such thing as a zoom mike.
Shorter hypercardioids such as the Sennheiser MKH-416 or MKH-60, Neumann KMR-81i, or Sanken CS-3 have a broader angle of acceptance than their longer brethren. Since the fall-off between on-axis and off-axis sound is considerable for all hypercardioids, you have to be quick panning the mike to a new speaker in a group.
FIGURE 27-12 Polar reception pattern for a Sennheiser® MKH-70 microphone showing the slight variations of sensitivity in different frequency bands. (Photo courtesy of Sennheiser Electronic Corp.)
With directional mikes, watch what may be making sound behind the subject since shotguns, like a telephoto lens, tend to squeeze background and foreground together. Angle the mike downward, and perhaps you can get that idling truck motor out of the mike’s “line of sight.”
Cardioid
Regular cardioid mikes have an angle of acceptance that is broader still. They are made by the manufacturers already mentioned, as well as well as by AKG, Audio Technica, Beyer Dynamic, ElectroVoice, Schoeps, and Shure—all of whom make a range of mikes. Use cardioids or even omnidirectional mikes for covering a group discussion, as people tend to speak unpredictably from several directions and ultradirectional miking becomes a handicap.
All microphones register air currents, even indoors, as an intermittent rumble.
Dynamic cardioids are an older design that—unlike sensitive, battery-powered electret condenser mikes—is completely sound-powered. Though less sensitive, they are rugged and will endure the very loud sounds, rough handling, or temperature and moisture extremes that would disable their more delicate cousins.
Lavalier
The tiny, normally omnidirectional lavalier is usually of an electret condenser design. This allows them to be highly sensitive, full spectrum, and miniature. Some, like the Countryman B6 or the Sanken COS-11 (both waterproof), are tinier than a match head yet give superb sound. Other industry favorites are the TRAM® TR-50B, Sony® ECM-55, PSC MilliMic, or the Sennheiser® MKE 2. Each lavalier comes with a small globular foam windscreen that fits over the mike to inhibit popping on speech plosives. You can even customize the Countryman B6 by using different caps that alter its audio profile.
The sterile “studio” quality of lavaliers may work for or against you, depending on the needs of your film. Expect a level drop-off if the person turns their head and marked reverberation changes when the person approaches a hard surface.
All lavalier mikes suffer from air current and clothing interference sensitivity, with silk, rayon, nylon, and corduroy being among the worst offenders. Pin or tape clothing so it doesn’t rub or tap the mike.
If air currents become particularly troublesome outdoors, wrap the lavalier in cheesecloth or bury it in the wearer’s clothing (Figure 27-13). Feed a lavalier into its own wireless transmitter or, for minimal interference, wire it direct to the mixer board or camcorder. Tape the XLR connector of the lavalier to the wearer’s ankle for easy disconnection between bouts of filming.
FIGURE 27-13 Lavalier mike hidden under clothing for best protection against air currents.
Wireless Microphones
Imagine lavaliers on several moving participants transmitting to receivers all plugged into a mixing desk. Now you can confidently record several people on the move. Well, yes and no. All wireless mikes, even the very best, are vulnerable to occasional radiofrequency interference, emergency service transmitters, dead spots, and so on. They take setup time, gobble batteries, and need channel changes. This all takes time, especially in cities where radio activity is more extreme. Think of them like cellular phones—useful but occasionally treacherous. The Lectrosonics® 210 range has a very good reputation and is an industry standard. Favored among lower price systems is the Sennheiser® Evolution 500 (Figure 27-14).
Even the best wireless mikes, like cellular phones, are vulnerable to interference and dead spots.
Check experienced users’ comments on the Internet concerning features for particular models—for instance, how many radio channels a system should have and how automatically and seamlessly it changes channels when encountering transmission difficulties.
What to Rent and What to Own
If you are filming a lot over a long period, it may be worth it to purchase rather than rent the basics such as a fishpole, cables, and digital recorder. Something better isn’t going to suddenly appear—as happens with camcorders. Having your own basic mike set, a mixer, and a tripod may all make economic sense, too. If you must shoot at short notice, owning your own camera may even be unavoidable, and owning your own editing setup is a must. Better to rent radio mikes, exotic lighting, or camera supports that you use once in a blue moon. If you must shoot at the highest quality for two weeks and then spend many months editing, it’s probably wise to rent all of your shooting equipment.
FIGURE 27-14 Sennheiser® Evolution 500 wireless transmitter and receiver. (Photo courtesy of Sennheiser Electronic Corp.)
One of the goals of budgeting is always to foresee whether owning or renting is most economic.
Going Further
For cost-conscious reviews and practical articles on all aspects of sound, go to Fred Ginzburg’s Equipment Emporium (www.equipmentemporium.com). An outstanding 72-page article on sound theory and practice, “Location Sound: The Basics and Beyond” by Dan Brockett, can be found published under the Ken Stone Index (an offshoot of Final Cut Pro) at www.kenstone.net/fcp_homepage/location_sound.html. More excellent instructional material is available at the Location Sound Corporation Web site (www.locationsound.com/proaudio/ls/index.html). For a wide range of up-to-date sound equipment, go to www.thebroadcastshop.com/. The Digital Information Network, at www.dvinfo.net, is excellent for all digital filmmaking matters.