|Vocal Recording Microphone Techniques
Written by Loren Alldrin - © 2006, Cengage Learning. Reprinted with Permission.
This article is an excerpt from the following book: The Home Studio Guide To Microphones.
The human voice is the most complex and flexible instrument of all, capable of an incredibly broad range of expression, tone and volume. There's also a great deal of diversity from one voice to the next, which mandates a flexible, try-anything approach to vocal recording. Your first-choice vocal mic may sound wonderful on a strong baritone and horrid on a breathy soprano.
Most engineers' favorite vocal mics are large-diaphragm condensers that tend to capture a large, articulate vocal sound suitable for most types of music. But some small- and mid-sized diaphragms can achieve a similar vocal quality. And dynamic mics, though not usually a favorite for studio vocals, can deliver the perfect sound for some voices.
Because mic selection makes such a difference on vocals, it's not uncommon for engineers to record the same vocalist with different mics depending on the song and vocal delivery. The big, breathy sound of a large-diaphragm condenser may be perfect for a ballad, while the smaller, more focused sound of a vocal dynamic may better cut through a dense, up-tempo arrangement. When it comes time to choose a mic for a given vocalist or song, try every mic you've got; you may be surprised at which one sounds best.
While directional mics are most common for recording vocals, an omnidirectional mic can be very effective as well. An omni will exhibit no proximity effect, allowing you to place the mic much closer without bass buildup. An omni is also less prone to create popping noises, eliminating the need for a pop filter. The lack of proximity effect will also make for a more consistent sound if the vocalist changes distance from the mic. There will be a corresponding drop in level, but no significant change in tone. On mics with variable patterns, you can get good results from the intermediate patterns between cardioid and omni.
A good starting mic position for vocals is directly on-axis with the mouth, 6 to 12 inches away. You may get a softer sound by placing the mic a few inches to either side of the mouth. Placement above or below the mouth can result in different vocal characters, which may be advantageous for certain voices. One popular off-axis mic placement is roughly 12 inches from the singer, at about forehead level, pointing down towards the mouth. Off-axis placement also has the advantage of reducing sibilance and popping.
Mic distance depends in large part on the room. A noisy or highly reverberant room (or one with poor-sounding acoustics) will require a closer mic placement, at which point proximity effect becomes a significant factor in the vocal sound. At six or eight inches away, certain directional mics generate enough bass boost to really muddy up a vocal sound. If your mic has a low-cut switch, it can clean up the bottom end of the vocal considerably.
Because most vocals are recorded at very close distances, even small shifts in mic or vocalist placement can make a dramatic difference in the sound. A shifty vocalist can make for punches or edits that are very obvious due to the change in level and/or vocal tone. When tracking vocals—especially with a directional mic—it's very important that mic distance and placement stay consistent throughout a session.
To this end, encourage the vocalist to make a mental note of his or her location. It may be helpful to have them frequently check the distance from their lips to the mic or pop filter with their fingers. As a last resort, place a line of tape on the floor where the vocalist can position his or her toes during recording. When miking from distances of a few feet or more, small changes in the vocalist's position are far less noticeable.
Sibilance is the bright burst of noise radiated by consonants such as "s," "t" and "f." With certain voices and mics, sibilance can be overpowering. One method for reducing sibilance with directional mics is to keep the mic directly in front of the mouth, while rotating it off-axis slightly. This reduces the high-frequency pickup of most mics and can eliminate problem sibilance. Ten or twenty degrees is usually enough to do the trick, depending on mic design and pickup pattern.
The most effective means of suppressing popping noises from plosives like "p" and "b" is the fabric pop filter. Stretched over a circular frame, the pop filter mounts to the mic stand or boom arm. Foam filters, whether inside the mic or placed directly over it, are rarely as effective or as acoustically transparent. If you're using a vocal mic with a built-in pop filter, try removing the grill and foam filter and placing the mic behind a fabric pop filter instead. You can easily make your own pop filter with a pair of pantyhose and a 6- or 8-inch embroidery hoop.
For the vocalist who insists on holding the microphone during recording, here's a trick for pacifying them while still getting a clean vocal track. Set up your vocal mic of choice at a safe distance from the vocalist. Attach any handheld mic to a second cable and give it to the vocalist. The singer can then belt their most inspired performance into the placebo mic, while you capture the take without compromise with the more distant mic. For more information, see The Home Studio Guide To Microphones.
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