Print Page

2/21/2013

Arizona band What Laura Says lays down tracks at The Farm.

Fig. 1. This is one of the more traditional ways to mike a guitar amp.

Fig. 2. Positioning the mic off-axis, and changing its angle, alters the amp’s tone.

THE BEST-SOUNDING mixes start with the best-sounding tracks. In last month’s Master Class, I covered methods for miking drums and bass. This time, let’s nail the vocals, guitars, and electronic instruments.

Electric Guitar The classic approach is to place a dynamic mic at near-contact distance from the grille cloth and let it rip, but placement matters—you can vary the sound considerably just by moving the mic a few inches.

An on-axis mic pointed directly at the center of the speaker’s dust cap (Figure 1) provides a bright, articulate sound. Moving the mic farther away from the center and progressively closer to the speaker’s edge provides a darker, warmer, less-edgy sound. I often place the mic out toward the speaker cone’s edge, but angled in about 45 degrees, so it’s aimed at the dust cap (Figure 2). This configuration usually provides a good tonal balance—not too bright or too dark. 

Other approaches include employing multiple mics, adding a condenser mic or two a few feet back from the amp as “room” or ambience mics, using a mic in conjunction with a direct box (for later re-amping or providing a signal for amp-sim plugins), or combining the miked sound with amp-sim hardware such as the Tech 21 SansAmp products, Line 6 PODs, etc. Assuming your audio interface has sufficient inputs, if you’re short on mics or mic preamps but still want to track the band all at once, consider trying some of these amp alternatives— when tweaked properly, they can sound shockingly good.

Typical mic choices for guitar amps include moving-coil dynamics such as the SM57, Audix i5, Sennheiser e609, and Audio-Technica ATM650. Ribbon mics like the Royer R-101, Cascade Fathead II, Beyer M160, MXL R144, and AEA R92 are also great choices for use on guitar amps (and their figure-8 response opens up lots of options when miking two cabs). While a ribbon’s high-frequency response is somewhat subdued compared to many condenser mics, this characteristic can minimize any harsh or abrasive qualities—yet its condenser-like, quick transient response still provides a clear, detailed sound.

Condenser mics can also work well on guitar amps. Classic choices include the Neumann U67 and AKG C-414 EB, but more modern versions of the 414 can also work well, as can other large-diaphragm condensers such as the Neumann TLM102 and Mojave MA-300. Earthworks’ SR Series multipurpose condenser mics, while often used for acoustic guitars, also work well with amps.

Indeed, many mics are suitable for electric guitar amps, so the “best” model for the job can easily change from song to song—or even from overdub to overdub. Using mics with different characteristic sounds on different tracks can help give them more distinct and individual tones, so they stand out more easily in the mix. Want to emphasize the attack or the treble in a jangly guitar track? Try a brighter microphone, such as a condenser. Want a smoother sound? Try a ribbon.

Acoustic Guitar Tip number one: Start with a great acoustic guitar. Put some new strings on it a day or two in advance so they’re fresh but have been on the guitar long enough to have had a chance to stretch and settle in so they’ll stay in tune. Finger-Ease or a little talc can come in handy for reducing finger squeaks.

Fig. 3. Compared to stereo miking, a single microphone can eliminate the possibility of phase cancellation.

Fig. 4. When stereo miking, sum the signals in mono and make sure you have no phase-cancellation issues. If so, moving one mic slightly may solve the problem of phase cancellation.

Fig. 5. X/Y miking is an option for obtaining a full-sounding stereo recording.

Small-diaphragm condenser mics are common choices for acoustic guitar, but large-diaphragm condensers can also work well. Even ribbon mics are suitable, particularly when trying to tame an overly bright guitar. Typical options include the MXL 603, Audio-Technica AT4041 and Pro 37, Oktava MK012, Shure SM81, Studio Projects B1, Royer R-101, and Beyer M160. For classical guitar players with a light touch, the Earthworks QTC Series is designed specifically for quiet, low-level sound sources.

One of the most common placements is positioning the mic about six to 12 inches directly in front of the 14th fret, angled in slightly so it’s pointed toward the fingerboard between the body’s edge and the sound hole (Figure 3). For stereo, you can add a second mic about the same distance away, but placed over the lower bout (the lower curve of the body) or just behind the bridge (Figure 4). Another option is a classic X/Y stereo pair, placed about 12 to 18 inches in front of the guitar. I’ll normally center this stereo pair so that it’s almost directly in front of the sound hole (Figure 5). Pointing a mic at the hole usually isn’t recommended because it can sound way too muddy and boomy, but in the X/Y pair’s 90-degree angle, the two mics will be pointed to either “side” of the sound hole instead of directly into it.

Vocals There’s usually nothing more important than the lead vocal in your recording, because it’s the element the average listener “connects” with the most. The human voice conveys a lot of emotion in addition to the main melody and the lyrical message, so it’s crucial to get it right.

Start with the singers: Make sure they’re healthy. To cut down on phlegm, I recommend singers avoid dairy products for at least 24 to 48 hours before the session. Have lots of water available, but not ice water; if it’s too cold, the vocal folds can stiffen and contract. Stay away from syrupy beverages such as sodas, and acidic ones like orange juice. Comfort can be crucial for vocalists—kick everyone else out of the room if the singer finds others distracting, or if they make the singer feel self-conscious.

Mic selection will depend mostly on the singer’s style and the type of sound you seek. Many modern recordings feature lead vocals recorded with a large-diaphragm condenser. Over the past several years, there’s been a trend toward using mics with a fairly bright-sounding top end to help a singer “cut through” a busy mix. However, that same brightness might not be appropriate for a singer with a more treble-y or sibilant-sounding voice. Common choices include the classic heavyweight mics like the Neumann M49, U47, and U67; the AKG C12; and the Telefunken ELA M251. On a more real-world budget, the AKG C-414, Mojave Audio MA- 200, Studio Projects C1, Avantone CV-12, MXL V89, and RØDE NT1A are all respectable choices.

Start with the mic placed six to 8 inches away from the singer’s mouth, with a pop screen half-way between the two (Figure 6). Moving closer can give a thicker, fuller sound from the proximity effect, and can also be useful for a super-close, intimate sound. Moving back to around a foot from the mic tends to minimize the proximity effect. Using a baffle or other audio isolation tool (such as the sE Electronics Reflexion Filter or Primacoustic VoxGuard) to the sides of, and behind, the mic can help reduce room ambience pickup.

Moving-coil dynamic microphones are often useful too; some very successful records have been made with them. Classic mics to consider are the Shure SM7b and SM58, Sennheiser MD441, and Electro-Voice RE20 and RE320. And don’t forget ribbons! Before the dawn of condensers, the RCA 44 was frequently used, and other modern ribbon mics can also work well for vocals— especially if you’re after a smooth and sweet “crooner” sound.

With background vocals, you can overdub individual vocalists one track and part at a time. This is a good approach if the singers aren’t as prepared as they should be, or if you think you might want to process (or correct) the vocal tracks individually. An approach that requires more advance rehearsal is to position all the singers around a single omnidirectional mic and have them sing their backing parts simultaneously (Figure 7). Adjust the singers’ balance by moving individual singers closer to, or farther away, from the mic until you like the blend. You can then double-track or “multitrack and stack” them for panned stereo and to give the impression of a larger group of singers, or for thicker-sounding parts.

Fig. 6. A good pop filter can help reduce plosives, thus reducing the need to edit them out when mixing.

Fig. 7. Giving some distance to background vocals also gives depth, which can help during mixdown to differentiate the background vocals from the lead vocal.

While mics used for lead vocals can also be effective on background vocals, consider making two changes from the lead-vocal miking approach. First, vary your mic if a suitable substitute is available. This technique will help differentiate the backing vocals from the lead vocal parts, even if the same person overdubbed all of the tracks. If the lead vocal sound is lower and darker, try using a brighter-sounding mic when recording the background vocals. Second, move away from the mic a bit. Remember—distance equals depth. Physically placing the background vocalists anywhere from one to three feet farther away from the mic than the lead singer gives a different, less up-front sound that will help put them into a different space when you go to mix.

Whenever you’re recording any vocals in close proximity to the mic, use a good pop filter or screen to help cut down on plosives such as p-pops. These screens are also very useful for establishing a “minimum working distance” from the mic.

Synthesizers and Electronic Instruments While synths and drum machines don’t need miking, sometimes they can have an unnatural sound when mixed with acoustic or amplified instruments. Getting a mic into the equation is often the solution.

With electronic instruments, space truly is the final frontier. Although we listen through air, hardware and virtual synths generate electrical signals that need never reach air until we hear the final mix. Compared to acoustic instruments, synth sounds are relatively static—especially since the rise of sample-playback machines. Yet our ears are accustomed to hearing evolving, complex acoustical waveforms that are unlike synth waveforms, so creating a simple acoustic environment for the synth is one way to end up with a more interesting, complex sound. This technique can also help synths blend in with tracks that include miked instruments, because they usually include some degree of room ambience (even with fairly “dead” rooms).

Sending some (or even all) of your synth’s signal to an amp and miking it can give that feeling of “air.” For a clean sound, the Fender Twin is an old standby; but an amp like Line 6’s DT25 or DT50 is an excellent choice, as it’s possible to change the amp’s topology in the analog domain to generate anything from clean to dirty sounds.

Fig. 8. If you need more low end when using an amp with electronic instruments, try turning it into a pseudo-“closed-back” cabinet.

Virtual instruments can take advantage of this technique too—just pretend you’re re-amping a guitar track. Send the virtual instrument output directly to a hardware audio output on your computer’s audio interface (this assumes that your interface has multiple outputs), pad down the output, run it into your amp, then feed the mic into a spare audio interface input and record this signal to your DAW. There will likely be some delay introduced when going from digital to analog then back to digital again, but you can always compensate for this by “nudging” the miked track a little bit earlier.

One issue with open-back guitar amps is that they often lack low end. A quick fix is to place the amp so its back lies against the floor (preferably one with a rug), essentially turning it into a closed-back cabinet (Figure 8). However, note that with many amp designs, ventilation happens through the cabinet back—so this technique could block the airflow, which can be particularly problematic with tubes. In this case monitor temperatures carefully, and record for as short a period of time as possible. Whenever you take a break, move the cab back to its usual position to let it vent for a while. Even if the amp appears to be performing properly, heat buildup can reduce component life. (See our Web extra for more tips for getting a closed-back cab sound from an open-back cab.)

Another way to add the feel of an acoustic space to a synth is record the sound of the keys being hit. (Sometimes a contact mic works best.) Mix this very subtly in the background—just enough to give a low-level aural “cue.” You may be surprised at how much natural quality this technique can add to synthesized keyboards.

General Tips Now that we’ve gone over individual miking applications, let’s zoom out and consider some tips that apply to a variety of tracking situations.

• While close-miking techniques can reduce the influence of room acoustics, the location of your instruments and mics in a room can affect your overall sound quality dramatically. Avoid boomy-sounding corners, and don’t set up too close to walls that might contribute unnatural reflections. If your room is less than ideal, move the mics in close and use as much baffling and broadband absorption around your instruments and mics as possible. You’ll have to “add in” early reflections, ambience, and reverb at mixdown, but this is often a better approach than capturing negatively-colored room reflections that you won’t be able to remove from your tracks later.

• Don’t close-mike everything if you can avoid it, because then everything may wind up fighting for the up-front placement in the mix. Give some advance thought to varying the mic distances for various sound sources— consider moving the mic positions farther away from the source for supportive elements than for main elements. This configuration provides more “breathing room” in the mix, and helps the parts sit in their own “space.”

• Remember that when using directional mics, the proximity effect comes into play. Omni mics, however, can be placed ultra-close without any significant bass boost. Also remember that omni mics capture more of the room’s character and ambience than cardioid mics.

• Watch your recording levels—leave yourself some headroom to avoid any digital “overs” or unexpected peaks that go “into the red.” Ideally, track with levels averaging around –8dBFS to –15dBFS on your DAW meters. If your meters aren’t calibrated, I recommend recording at levels that average about halfway up the meters. Occasional peaks that go higher are okay, but never light up that clipping indicator!

• EQ and compression are fantastic tools, but don’t reach for them first. Consider changing an amp’s tone controls, adjusting the mic position, or even using a different mic. If the ribbon mics you’re using for the drum overheads sound too dark, try some condenser mics instead; if the guitar amp sounds too bright, reposition the mic.

Phil O’Keefe is a multi-instrumentalist, recording engineer/producer, and the Associate Editor of Harmony Central. He has engineered, produced, and performed on countless recording sessions, with artists such as Alien Ant Farm, Jules Day, and Voodoo Glow Skulls. His articles have also appeared in Keyboard and Guitar Player.

  Print Page