The first approach to picking sound gear is to consider: Is production audio run straight into camera or to a separate recorder? When audio is recorded separately, it’s called “dual system” sound. Typically a high-quality field mixer will receive sound from the microphones and mix down all the audio sources on set and feed that downmix to the camera. This means the picture and high quality audio will have to be synced in post.
Often times it’s simply not worth the effort to sync. The electrical signal generated by the mic is amplified several times before it’s loud enough to be audible. It’s the quality of the “pre-amplifier” or “pre-amp” that suffers in pretty much all video cameras. This is why it’s frowned upon to record audio straight into the camera. You can plug a very nice microphone into a DSLR but you’re still limited by the preamp. One option is to use a ‘hot mic’ with a strong enough level that the preamp isn’t actually amplifying much. In this case you turn your camera’s preamp to its lowest setting and still get decent audio. A compromise exists between the syncing hassle of dual system sound and the inferior quality of video camera pre-amps. The compromise is simply dedicated, higher quality preamps, that sit outside the camera and feed an already-amplified-as-much-as-possible signal to the camera. It adds bulk but increases control. These usually come with additional benefits: physical gain controls, phantom power, and XLR inputs to name a few.
The “signal chain” of an audio signal passes through various components. Generally speaking, the more you divide each of these steps into its own piece of gear the greater the audio quality at the cost of less convenience (and higher price).
The more devices you insert into your signal chain, the more you need to monitor and optimize gain at each stage of that chain.
Much of well-recorded audio involves getting a “hot” or “juicy” signal that doesn’t clip. Record at too low a level and the audio signal itself is hard to separate from the noise and too hot and the signal will distort or clip. There are often several places you have to check these levels (e.g. on the wireless mic transmitter, on the wireless mic receiver, and on the camera’s mic input) a process known as “gain staging”.
Newer devices with 32-bit floating point modes make this significantly simpler.
Some field recorders will have a separate “Gain” setting in the menus and along with a dedicated “levels” physicalThis is the main knob you use to control the input level on your audio device. You’ll always want to keep your peaks below -3dBFS, even in a very controlled recording environment. About -12dBFS average is a very general target for recording dialog, but if you can, record at 24 bits or higher and at a softer level (e.g. -18 dbFS) to maintain the aforementioned headroom. The headroom is useful in case of a loud laugh or unanticipated performance.
Gain staging refers to adjusting an analog audio signal’s levels at multiple points in the capture chain. This will vary depending on the gear your using, but the important concept is that you check your levels at every point you have the ability to adjust them and work from the sound source back to the recording source making sure they’re optimized along the way.
A microphone has increased sensitivity to a certain area around it. This is important to know when picking your mic.
These are the most common form of microphone for film and video use. They require power and are potentially more fragile, but they are high quality and robust for film sets.
Shotgun mics or “boom mics” are directional mics that are usually positioned just outside the frame.A receiver (Rx) and transmitter (Tx) can be used to send audio signals wirelessly, though it’s never as reliable as a wired connection. It’s important to monitor a wireless connection as interference is a very common occurrence.
Also called “lav mics”. Small microphones, usually condensers, that clip onto the talent and can oftentimes be hidden. Because these are often times condensers, they will require power. I generally suggest avoiding lavalier use if you have the alternative of a mic with a larger diaphragm. The lav’s sound is simply inferior.
Why do some lav mics need a battery and others don’t? “There are two powering systems in general use today:1) Consumer/Prosumer Mic Power, exclusively used with 3.5mm connections & other small connectors to wireless body pack transmitters. Nominally 5 volts dc, varies from 3V to about 7. This power can directly bias (“bias” power or “plug-in power”) a condenser mic, no preamps or other electronics in-line.
Some microphones will do their own “Analog to Digital” conversion meaning they simply plug into your computer via USB rather than requiring an “A to D” converter box. For the purposes of video making, this is generally not what you want.
Stringing a wire between a microphone and the camera can be inconvenient, and sometimes impossible. There are a huge variety of sources for wireless sound nowadays, but generally speaking there’s a bit of a quality hit and the risk that your signal may be interfered with.
Virtually all pro wireless systems operate on either the VHF (very high frequency) or UHF (ultra high frequency) bands. VHF wireless systems generally operate within the 174 to 216MHz range (the range of TV channels 7-13), while UHF uses the 470 to 805MHz range (the range for TV channels 14-69).”Both of these bands are becoming crowded though UHF is generally still considered superior. The analog signal can be “companded” to reduce its dynamic range/signal bandwidth or can be converted to digital before transmitting. These tricks help make the most of a crowded spectrum, but this conversion can increase latency as it has to be reversed by the receiver. Lectrosonic and Zaxcom, Audio Limited A10, are the higher end of the “industry standard”. These systems are built for reliability and rigorous production use. Sennheiser “G” series has been historically popular for more budget-friendly (sub $1000 options).
Disclaimer on spectrum availability: Anyone with systems that operate above 608 MHz must discontinue use and migrate to new frequency ranges. Sennheiser’s G4 series is future-compatible. Older G2 and G3 systems using the “A” range below 600 MHz may still be compatible. It’s not likely the FCC police will be after you unless you’re using these devices at extremely popular sporting events, but you may find your device subject to so much interference (from T-mobile traffic) it becomes problematic. See here for FCC details.
These use the same frequency band as WiFi and bluetooth. This is nice in that you can use your gear internationally without a problem, but bad in that you’ve got major competition from lots of consumer gear. Generally speaking, this ‘digital range’ doesn’t penetrate walls as well as the lower frequencies historically used in ‘professional’ audio gear will. RODE Link Wireless Filmmaker Kit, Deity Connect, and options from Saramonic are long-awaited competition to the G-series Sennheiser standard. XSW-D Sennheisers with a decent blend of features. Sennheiser AVX (Pro version of XS below)Sennheiser “XS” seriesNew Sennheiser XSW-D series operates (like RODElink) on 2.4GHz (aka WiFi) spectrum. Great review here.The system is smart about jumping to available WiFi bands quickly. Its one-button approach is great for new users intimidated by gain staging and pairing, but it’s a limitation in that there’s no gain control should your camera have a hot input.Built-in battery lasts around 5 hours per charge.The upgrade ME2 version II lav mic is much better than the original (bundled with G3 kit).Latency is great for a digital system.XLR transmitters available but they don’t provide phantom power.
The RodeLink runs on the same open frequency band as wifi networks (2.4GHz). It shares bandwidth with a LOT of consumer devices so you’re going to get more interference and less range due to the higher frequency and increased RF noise. A more recent announcement, at a price point that’s hard to compete with, is RODE’s new “Wireless Go” system. It’s also a 2.4GHz system, but it’s very clever about scanning available frequencies and quickly adapting to best use what’s open. It’s not going to be nearly as reliable as the non-digital, lower frequency band units, especially when the transmitter and receiver don’t have line-of-sight between each other.
So you’ve got a mic, and some way to carry its signal, but what are you recording into if not your video camera?
These are small units featuring both microphone and recorder in a single package. Though you can plug an external mic (typically a lavalier) into them, that’s not their primary use. Popular units include the Zoom H1 or Tascam DR-05:
The Zoom F1 is quite an innovation. It can act as a recorder for a variety of devices: lav mics, shotgun mics, etc. It has a headphone out so you can record to the camera and it also works as a USB interface for recording on your computer.
Professional sound recording on-location is usually done with a dedicated device like these. The recorded audio can be recorded to onboard memory (SD and micro SD) or piped back into the camera so you don’t have to sync in post. The high end devices will even use AES outputs for sending a digital signal to the camera so you bypass the camera’s cheaper A>D conversion and don’t require sync in post. Make sure your camera’s own “input level” is set quite low so its inferior pre-amps aren’t doing any of the heavy lifting. Many of these also act as USB interfaces (analog to digital converters) for plugging into a PC. They also feature compatibility with third-party physical controllers (and regular USB keyboards) and app support (not so handy for adjusting gain but very nice for metadata entry). The high end versions of these have cool features: Zaxcom: Dual A>D converters for “never clip” feature; remote levels control of wireless transmitters;Sound Devices 633, a $3500 field recorder.
Recently, Zoom released their F4 which represents the best value and pro-level feature set to date for $500:Low noise, high quality and high gain pre-amps and impressive dynamic rangeAccurate internal timecode clock and ability to jam syncFalse Take feature (Press rewind)Dual record feature for safetyAlso acts as a USB audio interface
That said, one affordable approach is to simply use the recording device you’ve already got: your phone. Inexpensive mics can plug into your 3.5mm headphone jack if you’ve got on and there are many apps that can record the signal.
For even greater quality, you can buy a mic with the Analog to Digital conversion built into it. These connect via the lightning connector on an iPhone. Google the Zoom iQ7 (≈$95) or Shure MV88 (≈$150).
TRS connectors are common 3-conductor setups which can be used for a mono or stereo mic. “Tip Ring Sleeve” comes standard in 1/4″ and 1/8″ varieties. The 1/8″ is also known as 3.5mm or just a “regular headphone jack” and it’s the one you’re most used to seeing on your consumer audio device.
The most common professional audio connector you’ll see used with microphones. It’s a balanced connector meaning positive, negative and ground are separated.
For much prosumer work, at short runs, XLR/balanced audio isn’t as big a deal as some make it out to be. You’re audio quality doesn’t immediate drop when being passed through a 3.5mm connector vs. an XLR. Once you’re past six feet you may experience issues. Definitely don’t try taking unbalanced audio runs over twelve feet.
Most professional mixes will have a +48 volt “phantom power” for powering condenser microphones.An audience is often enormously forgiving of picture quality, but not so with the sound, making bad audio a curse of amateur filmmaking. This is very different from the “plugin power” of 3.5mm microphones.
A twelve foot stereo headphone extension cable is frequently used to provide convenient distances from subject to camera for wired mics.This only works with cameras, recorders, or mixers that provide mic power on a 3.5mm jack. Audio Technica (others?) supply a similar mic with a couple button-size batteries in-line for power. There are “power box” suppliers, too, typically a 9v battery system. All of these are based on 3.5mm connectors, except in the case of wireless mic body packs, which can have any of a variety of small connectors. This is called “plugin power”.
Prosumer/Professional Phantom power is nominally 48v. Some systems only supply 24 or 28v, which doesn’t work on all mics, especially large-diaphram condensors. A mic’s specs will state what’s required, a camcorder’s, mixer’s, or audio recorder’s specs will state what they supply. Phantom is (almost) entirely a XLR connector system. Such balanced systems can usually run a few hundred feet when properly wired.””All condenser microphone elements need a few volts of bias voltage, which is often derived from phantom power but need not always be. Many condenser lavaliere microphones these days are used with wireless bodypacks, and those usually don’t supply phantom power (but do supply a bias voltage). There have also been various condenser microphones made over the years that require a separate battery rather than phantom power.” “Bias is a dc voltage (1.5 – 9 volts typically) that is provided on a single conductor. Unlike phantom power, bias does not require a balanced circuit.” “not all external microphone powering is phantom power. The term “phantom” refers to the invisibility of Phantom power, which does not need a dedicated power wire but rides invisibly on the two balanced mic cable conductor wires. When you need it, it is there, when you don’t need it, it isn’t (barring problems with cables or connectors). Mic powering that is delivered on balanced cables in this manner is correctly identified as phantom, regardless of the voltage. “To confuse this understanding, very often ANY powering of condenser microphones is incorrectly called “phantom” even when it is delivered on a dedicated wire or via a battery.Many lavs designed for video/film include a preamp body that can be powered off a single 1.5v AA battery and/or phantom. A few shotguns, too.It takes a converter to plug a lav mic into an XLR input. Though it appears to be just an simple adaptor, the MZA900P converts Phantom Pwr. to a usable ‘bias current’ ( sometimes referred to as ‘Plugin Power”) Using the mic with just a cheap 1/8″ to XLR adapter with Phantom power. could permanently trash the mic.