Guitar Amp Recording Part 2
Written by Mike Senior, SOS
Dynamic Mics For Electric Guitar
When it comes to recording electric guitar, Jay Graydon's (Producer - Airplay, Jarreau) views on mic choice are pretty clear: "I have tried so many dynamic mics over the years, and always come back to the Shure SM57." He's not alone: this robust, cardioid, dynamic microphone is more often mentioned in relation to electric-guitar recording than any other. Why such a strong preference? These days, force of habit has got to be part of the answer, but there is also a lot about the microphone's frequency response which suits guitar recording. For a start, the sub-200Hz response roll-off reduces low-end cabinet 'thumps', which might otherwise conflict with the kick drum and bass in the mix. This also compensates for proximity boost when the mic is used very close to the speaker cone.
However, there's also a slight 'suckout' at 300-500Hz, an area where muddiness can easily occur, and a broad 2-12kHz presence peak, which adds bite and helps the guitars cut through the rest of the track. Producers as varied as Chuck Ainlay, Mike Clink, Mike Hedges, Gil Norton, Bob Rock, Elliot Scheiner and Tony Visconti all claim to have recorded electric guitar using this mic alone, and it would probably be fair to say that it's often the first mic to come out of the locker for many more than these. Sennheiser's cardioid MD421 crops up almost as frequently in interviews, and has a wider frequency response, none of the low mid-range suckout, and an even heftier sensitivity boost upwards of 1kHz.
This microphone also has a larger diaphragm than the SM57, and the off-axis response anomalies of the larger diaphragm, in particular, give a different character to the sound. Although obviously very popular, this mic seems more often to be used in combination with other mics than on its own. The same goes for Electrovoice's RE20, which counts Steve Albini, John Fry, and especially Glenn Kolotkin amongst its friends. "I like to use RE20s on most amplifiers when they're available", says Glenn, "because the quality is great and they can take really high levels. They're very directional and they're great for rock and roll." The mic also exhibits an unusually wide and flat frequency response and is specially designed to resist proximity effect. For a rock sound, many (though not all!) engineers will use a dynamic mic placed close to the speaker (sometimes on its own, sometimes in combination with other mics). Shure's SM57 (left), Sennheiser's MD421 (centre) and the Electrovoice RE20 (right) are popular choices for this application.
Condensers & Ribbons
Alan Parsons: "I always use condenser mics on a guitar amp, never dynamics they're too telephoney. That's an unfair expression for a very good dynamic mic, but by comparison to a condenser, you're not going to get the bottom end." While this stance is more hard-line than that of most engineers, condenser mics are, of course, regularly used for recording electric guitars. However, in practice they rarely seem to be used on their own and are very often lined up alongside the trusty SM57. Large-diaphragm models are popular, with Neumann mics particularly favoured. The famous U87 studio workhorse is probably the most commonly mentioned, but it's by no means the only contender. Eddie Kramer, Steve Albini and John Leckie single out its predecessor, the U67, for example, while both of the earlier U47 models (valve and FET) receive name checks from people such as Steven Street, Glenn Kolotkin, Butch Vig and Bruce Botnick (note that U47s were marketed under both Neumann and Telefunken brand-names, but they're essentially the same mics). Neumann aren't the only game in town, though: AKG's C414B-ULS is probably joint most popular large-diaphragm model alongside the U87.
The characteristics that producers most often seem to be looking for in these mics are their extended frequency response, especially at the low end, and the slightly softer, more diffuse sound imparted by the large diaphragm. These mics also tend to boost the 5-15kHz region, but this boost is rapidly lost as you move off-axis (it is inherently difficult to design a large-diaphragm capsule with an even off-axis frequency response). Small-diaphragm condenser mics, on the other hand, tend to have flatter frequency plots and a better-behaved off-axis response, giving a sound sometimes described as more focused, but they seem to be less commonly chosen by the interviewees than large-diaphragm ones. Neumann's KM84 seems to be the most regular choice of small-diaphragm condenser, and numbers John Fry and Bill Price amongst its high-profile users, while Sennheiser's MKH40 warrants a particular mention from Mike Hedges: "I started using [these mics] when I was working with the Beautiful South. I started off with two and now have more than 20. I think they were originally designed for classical recording, because they have very high gain and very low noise. This means that you can get a very clean sound. They also accept massive amounts of volume, so you can put one against a guitar amp on full and it will take it." Hedge's concern about the ability of the microphone to handle the sheer volume of some guitar amps is echoed by several of the other producers, who make a point of mentioning that they switch in a condenser's 10dB pad when recording electric guitars.
Surprisingly, perhaps, given their reputation for fragility, ribbon mics also seem to be widely used for electric guitar, with models from Beyerdynamic, Coles, RCA and Royer all putting in appearances. Producers using ribbons include Thom Panunzio, Joe Barresi, Steve Albini, Ed Cherney, Bill Bottrell and Butch Vig Eddie Kramer even goes as far as to say that "to me, the best guitar mic is the Beyer M160, which I've used for 30 years on Hendrix, on Zeppelin, on everybody." One trait of most ribbon mics is the figure-of-eight polar response, and this is often exceptionally consistent across the frequency range. This polar pattern means, of course, that ribbons tend to pick up a little more room ambience than cardioids, given that the polar pattern is as sensitive behind the diaphragm as it is in front. Ribbon mics are also often characterised as sounding 'smoother' compared with typical condenser microphones, partly because their construction avoids the high-frequency diaphragm resonances normally inherent in condenser designs. Popular condensers: when it comes to condenser mics for guitar-cab miking, the AKG C414 (in its various flavours the C414 B-ULS is pictured above left) and the Neumann U87 (centre) are both popular choices. Some producers also frequently look to the U87's predecessors, the U47 valve (pictured) and FET models, and the U67.
Audio Examples: Mic Placement These examples show how different mic positions can affect the tone of a recorded guitar cabinet. ConeCentre ConeEdge ConeMidway
These examples were recorded simultaneously via three on-axis SM57s, directly on the speaker grille: the first at the centre of the cone, the second at the edge, and the third midway between the two. ConeCentre0Degrees ConeCentre22Degrees ConeCentre45Degrees
Three SM57s were placed as close as possible together at the centre of the speaker cone and directly on the speaker grille. The first was on axis, the second was angled at around 22 degrees and the third at around 45 degrees. AndyJohns
Here, I have combined the on-axis and 45-degree mics to give some idea of the range of sounds available using the technique mentioned by Andy Johns. At the start of the audio example only the on-axis mic can be heard, but then the other mic fades in until, by the middle of the example, both mics are at equal level. Then the on-axis mic fades out during the remainder of the audio example. Grille 1Foot 3Feet
Here, three SM57s were placed on-axis at different distances from the centre of the speaker cone. The first was right up by the grille, the second at 12 inches, and the third three feet away.
The speaker cone of a guitar amp will sound different when close-miked at the centre than when miked at the edge: it is worth experimenting to get the sound you want.
The angle of the mic in relation to the speaker cone will also affect the sound
How far away from the speaker cabinet the mic is placed has a significant impact on the recorded sound.
Article courtesy of Sound on Sound Magazine