Miking up a guitar amp is precarious ground with multiple factors at play. There are tried-and-tested techniques but nothing is ever set in stone on the quest for those fat, glorious tones.
Capturing the best possible electric guitar sound has long since been one of the most important components in the field of modern recording. Since the innovations of Leo Fender and his contemporaries, the electric guitar has shaped entire styles of music, having an impact like no other instrument.
You might assume that there would be a textbook procedure for miking guitar amps — it being such a crucial instrument — but recording the sound of an amplifier has almost as many methods as there are different models.
Starting at the Source
Before attacking the amp with tape measure to fine-tune your phase alignment or microscopically analysing the driver for the perfect position for your microphone, the most practical advice is get the sound right coming out of the speaker.
The raw, unrecorded tone should be exciting and the player and engineer alike, and a degree of latitude should be given to experimenting with guitar sounds. There are practical concerns to be addressed in this process too, for example, getting the gain staging in the pedal chain (if you are using pedals) correct in order to avoid large discrepancies in level when engaging different pedals.
Obviously, it’s a massive vibe-killer to spend too much time on these tasks, but making sure that everyone is happy with the source sound is crucial.
Finding your Place in a Room
Finding the best location for the guitar amp in the room should also be a priority. The sound coming from the amp will reflect off walls and then hit the microphone later than the direct sound. If the room is particularly live, and the reflected sounds are close in amplitude to the direct sound, there will be problems with phase cancellation.
Finding the right spot – lifting the amp or angling the amp – are all practical options for minimising reflections and/or maximising resonance and achieving desirable frequency response.
Choosing Your Weapon
Dynamic microphones tend to be the most popular choice for miking up amps. This is largely due to the characteristics of dynamic cardioids: a slight rolloff sub 200hZ, which tends to eliminate rumbles and general muddiness, and a slight, but broad higher frequency peak, which tends to give the electric guitar more presence in the mix. Microphones like the Sennheiser MD 421, e906 and the Electro-Voice RE20 tend be trusty recording studio studio staples for this purpose, yet the most used of all would have to be the trusty (if highly disputed) Shure SM57.
Large diaphragm condensers get a fair workout in front of guitar cabs too. They offer a wider, frequency response than the more coloured dynamics and they still maintain that pleasing top end. Large diaphragm condensers do tend be quite expensive, so if you’re miking up a whole band and a large diaphragm condenser is more useful elsewhere, it might affect your miking decision.
Ribbon mics are very desirable for guitar amps. The figure-eight polar pattern means that it picks up natural reflections of the room. They tend to be smoother in response to high-end information – for the same reason they are popular with brass, the ribbon design minimises harshness.
Though modern ribbons are far more robust, the warning still applies – they are fragile, so they’re not recommended in very high SPL situations.
This is where the rulebook really goes out the window. Throughout modern recording, it is surprising to see how many methods are subscribed from so many of the industry’s most trusted practitioners. From the SM57 right on the grill, to omnidirectional condensers on the other side of the room, and everything in between. A common sense approach can be helpful though.
It stands to reason that the best sound may be achieved in a more ambient position, because when tweaking amp settings, the player doesn’t usually have their ears right next to the driver.
Using a combination of microphones might also prove useful. If your usual go to is a coloured and toppy SM57 or e609, why not balance that tone with a mic that can respond better in the bottom end, like a Royer R121. Another technique for increasing tonal variation is to use two of the same microphones, one directly on axis, the other at an angle. Having a balanced tone from two different microphones (or two different microphone settings) will offer more tonal variations in the mix as well.
This article could be one in a series of pieces about electric guitars in sound production, because there are endless ways to experiment with pulling the best sound out of the guitar amplifiers you happen to be tracking. With equal servings of experimentation and common sense, you might go some way to achieving the best guitar amp sound for any given session.