Because of its fundamental importance in popular music, the electric guitar is the subject of intense scrutiny and wide differences of opinions. Just what makes a good guitar sound?
Compared to all the subtle and not so subtle sounds that come out of an electric guitar amp, fidelity judgments of vocal sounds are easy to make!
With good knowledge of the different guitar and amplifier sonic capabilities, coupled with good microphone techniques,we can achieve the ultimate guitar sound that “fits” the guitar part, song and production genre.
A good guitar sound starts with a good player with the right amp and guitar all working together. It’s unrealistic to rely on an engineer to make poor gear sound wonderful in the control room.
Microphone choices and miking techniques are good starting points for capturing and recording electric guitar amp sound.
Microphone Selection
Microphone choice (for me) is as big a part of the guitar amp’s recorded sound as the amp and guitar used, volume played and player choice, because the mic type and placement will greatly influence the player’s performance and tone.
Dynamics
The Shure SM57 cardioid dynamic is the most common microphone used to record electric guitar. This started back when all the more expensive microphones had already been used in big tracking sessions. Engineers were left with the “lowly” SM57 to handle those loud, cranky, noisy guitar amps.
But it turns out that the SM57 is perfect for the task; its frequency response, originally tailored for speaking, matches the mid-range “voice” qualities of the guitar. Italso has a compression effect on loud sounds – it squashes nicely, facilitating the engineer’s job of maintaining consistent recording levels.
You’ll see engineers push a SM57 right into the grill cloth of an amp cabinet, taking advantage of the proximity effect, which boosts low frequencies when the mic is placed close to a sound source. The SM57 locks in a certain “size” for the electric guitar, maintaining its appropriate place in the mix without additional EQ or compression.
The Sennheiser MD 421U cardioid dynamic is also popular, offering a wider frequency response (more high and low frequencies) than the SM57. A five-position rotary switch adjusts the frequency response from the flat position, called M (for music), all the way to the contoured S (for speech).
Generally, I find the 421 brighter with less of the compression effect than the SM57. These mics are also more directional, which is important for isolating the sound coming from one speaker in a multi-speaker cabinet.
Condensers
Condenser microphones also work great, but care must to taken to not get an overly bright sound. Your guitar player might complain that his amp sounds brighter than usual (compared to a SM57) and feel he must readjust his recording knob settings. As a result, I place them further away from the speakers.
Figure 1 shows a Shure KSM44 condenser about 20 inches from a 1960s vintage straight Marshall 4X10 cab. (I was auditioning the three cabinets in the picture).
Condensers pick up more low frequencies from the amp, and this may or may not be a good thing. Pushing a lot of air might work in a heavy metal track, but it also might be inappropriate for a lighter pop song.
I’ve also noticed certain condensers sometimes add distortion when close-miking extremely loud amps. Occasionally, the metal wind screen can get loose and vibrates. Always use the attenuator pad and maybe the low frequency roll-off. The Neumann U 87 and U-47FET, Shure KSM44 and Audio-Technica AT4041 are all good choices.
Condenser microphones also provide the opportunity to experiment with different polar patterns such as omnidirectional and Figure-of-Eight (see my article about this here). Omnidirectional mics do not exhibit the proximity effect and will pick up more of the total sound of the amp and room tone, rather than one particular speaker.
I like omni mics for more of an ambient guitar sound or for room mics. Figure-of-Eight mics also pick up more of the room, but only from directly behind the mic’s body opposite the front side.
