Equipment for Stereo Recording
Let’s describe in detail the gear you need to make a simple stereo recording.
A microphone changes sound into an electrical signal. Classified by how that is done, there are three types of mics for recording: condenser, dynamic, and ribbon.
Condenser, Dynamic, and Ribbon Types
Condenser mics typically give a clear, detailed, natural sound. They are the preferred choice for stereo recording. Condenser mics require a power supply to work, explained later under the heading “Mic Connectors, Powering, and Cables.”
Dynamic (moving-coil) mics work without any power supply. They are rugged and reliable. Most dynamic mics do not sound as clear and natural as condensers and are less sensitive, so dynamics are seldom used for stereo recording.
A ribbon mic provides a smooth sound that many people prefer, and it works without power, but it’s delicate and expensive.
Sound Pickup Patterns (Polar Patterns)
Microphones also differ in the way they respond to sounds coming from different directions:
• An omnidirectional (omni) mic picks up sound equally well in all directions.
• A unidirectional mic picks up sound best in front of the microphone. It partly rejects sounds to the sides and rear of the mic. Three types of unidirectional mic are cardioid, supercardioid, and hypercardioid. Each has a progressively narrower pickup pattern.
• A bidirectional (figure-eight) mic picks up best in two directions: in front of and behind the microphone. Most ribbon mics have a bidirectional polar pattern. Mics with this pattern are used in the Blumlein stereo technique, described in Chapter 9 . Figure 8-1 shows various polar patterns, and Chapter 8 describes polar patterns in more detail.
Which mic pattern is right for your needs? Choose omni mics when you need all-around pickup, extra deep bass, less handling noise and wind noise, or binaural (headworn) miking for headphone playback. Choose cardioid mics when you need sharp stereo imaging, rejection of room reverberation, and rejection of background noise and feedback.
Mic Connectors, Powering, and Cables
Mics come with either an XLR (3-pin) connector or a phone plug (called a “jack” plug outside the US). Most condenser mics with an XLR connector are powered by 12–48 volts of phantom power. This powering can be supplied by a phantom power supply, mic preamp, recorder, or mixer. Condenser mics with a phone plug (jack plug) either use an internal battery, or they receive DC bias or plug-in power (3–10 V DC) from a recorder. Some mics can be powered by a separate battery module, which helps the mic pick up loud sound sources with less distortion (increased dynamic range).
A mic with an XLR connector has what’s called a “low-impedance balanced” output. Such a mic can be used with very long mic cables without picking up hum or losing treble. A mic with a phone plug (jack plug outside the US) comes with a short, permanently attached cable or no cable. This type of mic has an unbalanced output that is low-to-medium impedance.
What if your mics have XLR connectors, but your recorder or mic preamp has one or two phone jacks (sockets outside the United States)? You’ll need an adapter cable.
Cheap 1/8-inch phone plugs (3.5 mm jack plugs) with thin gold plating are actually less reliable than plugs with nickel plating. Thin gold plating wears off quickly, exposing a brass surface that makes poor contact.
USB microphones have a built-in analog-to-digital converter and a USB connector, which you plug into a computer’s USB port. That lets you record the mic’s signal with recording software.
A stereo mic has two mic capsules in the same housing for convenient stereo recording. A mini stereo mic plugs directly into some portable digital recorders and Apple iOS devices. Mini stereo mics that use cardioid mic capsules tend to have less bass and more noise (hiss) than larger stereo mics. A headworn binaural mic has two miniature omni condenser mics that you wear in or near your ears; you play back the recording on headphones. Chapter 12 lists the websites of all these types of microphones.
You can make yourself a decent stereo or binaural mic for experimenting. Purchase some JLIelectronics JLI-61A omni mic capsules for $1.67 each. Get an adapter cable with a 1/8-inch stereo plug (3.5 mm stereo jack plug outside the US) and two RCA (phono) plugs. Cut off the two RCA (phono) plugs and solder the wires to the mics. If you want mics that are ruggeder, of higher quality, and better looking, check out the commercial mic websites listed in Chapter 12 .
Microphone Mounting Styles
Microphones also can be classified by the way they mount onto objects:
• Portable handheld recorders have mics built in.
• Plug-in mics plug into an iPhone, iPod Touch or iPad.
• A stand-mounted stereo mic attaches to a mic stand. A stereo pair of mics can mount on a stereo bar (stereo mic adapter), which holds two mics on a single mic stand. However, mic stands might be too large to be acceptable in certain venues, and they are a hassle to carry.
• “Goosenoose” stereo mics are worn around the neck.
• Clip-on mics can be clipped to a shirt at the shoulders or to eyeglass earpieces.
• Headband-mounted mics are attached to a headband. Some headband products have “street” styling.
• Desktop mics sit a few inches above a desk or a table, so they might pick up an unnatural, filtered sound due to surface-sound reflections.
• Boundary mics eliminate that problem by mounting directly on surfaces.
When you shop for a mic, consider these other specifications on the mic data sheet:
• Signal-to-noise (S/N) ratio: 67 dB at 1 Pa (Pascal) is fair; 74 dB is very good; 84 is excellent. But 67 dB is good enough if you are recording loud rock concerts.
• Frequency response range: 100 Hz to 15 kHz is fair; 50 Hz to 18 kHz is very good; 20 Hz to 20 kHz is excellent.
• Frequency response tolerance: ± 6 dB is fair; ± 3 dB is very good; ± 1 dB is excellent.
• Maximum sound pressure level: 100 dB is fair; 110 dB is very good; 120 dB is excellent (high enough for rock concerts).
• Size: Small-diameter microphones (under 1/2 inch) tend to be relatively noisy, but this may not be a problem if you are recording loud music. Omni mics of any size can have excellent bass. They pick up deeper bass than small cardioid mics, which sound “thin” by comparison.
• Accessories: A foam windscreen for recording outdoors is a handy accessory. If your mic lacks a windscreen, you can purchase one from Radio Shack (or a music store) and cut it to fit. A stereo bar or stereo mic adapter mounts a pair of mics on a single mic stand for convenient stereo miking.
Stereo Recording Devices
Having covered mics for stereo recording, let’s move on to the recording device itself. We’ll look at three different types: a flash-memory handheld recorder, an iPad with a recording app, and a laptop computer with recording software.
Flash-Memory Handheld Recorder
A flash-memory handheld recorder (Figures 1-4 and 1-5) is a portable digital recorder with no moving parts. Also called a solid-state recorder, it records into a flash-memory Secure Digital (SD or SDHC) card. A 2 GB SD card can store 2 hours of 24-bit/44.1 kHz WAV audio files. Flash-memory recorders can record MP3 files or uncompressed PCM WAV files (which are CD quality or better).
These recorders have a number of features to consider. Power comes from replaceable or rechargeable batteries. Available mic connectors are XLR, 1/4-inch phone (6.35 mm socket), or 1/8-inch phone (3.5 mm socket), with or without 48 V phantom power or plug-in power. Most recorders come with built-in stereo or surround microphones. Prices range from $100 to $1000.
After making a recording, you connect the USB (Universal Serial Bus) port in the recorder to the USB port in a computer. The recorder shows up as a storage device on your computer screen. You drag-and-drop the recorded sound files to the computer’s hard drive for editing and CD burning. The files transfer in a few minutes. Then the flash-memory card is empty, free to make more recordings.
Nearly all flash-memory recorders include a mic-gain switch to accommodate both quiet and loud sound sources. Low gain or low amplification (0–15 dB) is for recording loud sounds (rock concerts); medium gain (25 dB) is for recording medium sounds (acoustic music, lectures, or rehearsals); and high gain (50 dB) is for recording quiet sounds (nature, quiet talking). Most recorders have AGC (automatic-gain control), which sets the recording level automatically depending on how loud the sound is. Some units include a limiter to prevent recording above 0 dB level, which otherwise would cause distortion.
Google “handheld recorders” to see some examples.
iPad with a Recording App and a Plug-In Stereo Mic
Apple’s iOS devices, including the iPhone, iPod Touch and iPad, have loads of recording-app options. On the iPad, simply tap the App Store icon and search for recording apps. Install one, plug in a stereo iOS mic and start recording.
A few stereo recording apps are GarageBand, Sonoma Wire Works’ StudioTrack, RODE Rec, StudioMini XL, Tascam PCM Recorder, and n-Track Studio (http://ntrack.com).
Some stereo microphones are designed to plug directly into an iPad or other iOS devices. Google “ iOS stereo microphones. ” Six examples are the Rode iXY, IK Multimedia iRig Mic, Blue Mikey Digital, Blue Spark Digital, Zoom iQ5, and Tascam iM2.
If you want to use microphones with XLR connectors, you’ll also need an audio interface that plugs into your iOS device. Three examples are the Tascam iU2, the Alesis iO Dock, and the Focusrite iTrack Dock. Some devices connect to an iPad with a Lightning connector, some use 30-pin, and some use both.
Laptop, Recording Software, and Audio Interface
Another stereo recording device is a laptop computer with recording software. To get audio into the computer, use a two-channel audio interface. This is a mic preamp with two mic inputs and a USB or FireWire port, which connects to a similar port in your laptop.
An example of a two-channel USB audio interface is the M-Audio M-Track (Figure 1-7) (www.m-audio.com).
You can plug a USB stereo microphone directly into a laptop; then no audio interface is necessary. Google “USB stereo microphone” to find some models.
If your computer lacks a USB or FireWire port, get a USB or FireWire PC Card adapter. It is a PCMCIA card with a USB or FireWire port. Plug the card into your laptop and connect its port to the audio interface. Another option is a CardBus card, which is an advanced PCMCIA card with faster speed.
USB or FireWire PC Card adapters and CardBus adapters can be found in a Google search. Recording software is described under the heading “Computer DAW Recording Systems” later in this chapter. When a laptop recording is done, you are ready to edit it. You don’t have to transfer the WAV files from recorder to computer as you do with other methods.
Headphones or Earphones
Headphones or earphones let you know whether the mics are working correctly, and let you hear what the mics are picking up. Room noises that you wouldn’t otherwise notice become obvious when you listen on headphones. Also listen for buzzes, distortion, and crackles from bad cables or connections. If the band and PA are loud, it is hard to hear what’s being recorded unless you use isolating headphones (Remote Audio HN-7506) or isolating earphones (Etymotic ER-4S and ER-4P; Shure SE series.)
Excerpt from Recording Music on Location, 2nd Edition by Bruce Bartlett and Jenny Bartlett © 2014 Taylor & Francis Group. All Rights Reserved.