TELLING YOU WHAT YOU ALREADY KNOW
The basic design of the omni microphone is such that it captures sound in a full 360-degree, or omnidirectional radius (see Figure 1). Unlike cardioid, hypercardioid, or supercardioid mics that reject sounds from the side and rear, omni’s record that space. While you may be thinking, “I was taught to always minimize leakage”, quite often that ‘leakage’ is useful ambience. For example, when recording drums in a good room, I will often use a pair of omni mics as overheads or ambient mics. The room tone will often add life and depth to drum recordings, so why ‘reject’ it? Certainly, the better the room, the better the sound, but it also helps me minimize how much reverb I add in the mix stage. Try it for yourself and you’ll explore a whole new sound.
Another interesting fact about many omni microphones is that they can handle very high sound pressure levels (SPLs). As two of my favorites, the DPA 4007 microphone can handle up to 155dBs before clipping, and the Earthworks TC30K can take up to 150dB SPL. This lets you place them very close to a source without worrying about overloading — great for the aforementioned drum overheads, kick drums, or cabinet mics on electrics guitars. So go ahead and place an omni in front of a loud source — they can handle it with ease.
PLACE IN SPACE
Speaking of placement, another benefit of omnis is that they don’t suffer from proximity effect (the boosting of lows as you get closer to the source). This simple fact lets you place them closer to an instrument or amp if you choose to — therefore capturing more of the direct sound. If you want more ambience in the recording, just move the mics farther away from the source.
On live recordings, I often use a pair (or more) of omni mics placed out in the audience to capture the vibe off the stage and PA system. Often referred to as a ‘spaced omni’ approach, this delivers me plenty of left/right separation and provides the ‘natural’ feel of a recording — instead of just a dry mix with artificial reverbs. Sometimes I place them out with the Front of House (FOH) console. If that distance is too far and slapback occurs when raising the tracks in the mix stage, simply nudge them back in time. That allows you to create the exact distance you want the listener to hear — or feel for that matter.
Omni microphones tend to have very small capsules, which are quite simple in design. This provides a cleaner, more dynamic sound with a nice, flat, extended low-frequency response. The pair of Earthworks QTC-1s I own have a listed frequency range from 4Hz to 40kHz. These work great on acoustic instruments of any kind: bass, piano, strings/woodwinds, and especially acoustic guitars. Working with the late great engineer David Baker, we recorded Al Di Meola’s vintage 1930’s Martin using a pair of Schoeps cardoids in an X/Y configuration at the soundhole, with the Earthworks omni’s set about four feet from the guitar and four feet apart. The omnis, when mixed with the X/Y mics, added a beautiful natural sheen to the instrument and really opened up the sound. Think beyond mono, Grasshopper. . . .
Directional microphones are also more sensitive to wind/pop and handling noise than omni mics are because of their larger diaphragms. This led me to experiment with using an omni mic on vocals. I placed the mic pointing straight up at about the height of the singer’s chin, so the voice would project into the space just above the tip. We liked the sound so much we used it on every track on the record — without using a pop filter. In capturing the singer’s guitar (world/flamenco guitarist Hernan Romero), I used a pair of QTC-1s, with one pointed at the neck/soundhole position and one placed down by the body of the instrument. Panning each at the 3 and 9 o’clock position, they delivered a warm, punchy and “real” sound — exactly what the artist was seeking. Distortion, or lack thereof, is another positive characteristic of omni microphones. Flamenco guitarists can be very transient, and omni mics with their small diaphragms can handle the spikes and SPL peaks amazingly well — with no distortion.
Good omni mics can virtually eliminate the need for EQ, since their response is so smooth and accurate. On a recent hi-res recording up at Clubhouse Studios in Rhinebeck, NY, engineer Paul Antonell and I used four omni mics (stereo DPA 4006s and Earthworks QTC-1s) in the main room to capture the surround tracks. It was 11 pieces playing together live; a string quartet, several woodwinds, percussion, Peter Primamore on piano, Tony Levin on bass, Jerry Moratta on drums and Ciele Minucci on guitar. We placed the mics by finding the sweet spots in the room, and then simply went with our instincts. Panning the DPAs into the front left/right and the Earthworks into the surrounds, it feels like you’re sitting in the middle of all these great musicians. Also, the percussion (in isolation) was recorded with simply a pair of overhead omni’s — providing excellent transients and overall sound.
So if you’ve got an omni mic, or two, in the closet, and you’ve hesitated in using them, fear not. For a clean, clear, open sound, you simply can’t beat the omni.
Pluses: Extended low-frequency response, can handle high sound pressure levels (SPLs), captures sound equally in a 360-degree field, no proximity effect, great for ambient room/live miking.