In many combo amplifiers, the speaker is not actually in the center of the cabinet, and may not be easily visible through the grill cloth. In this case, shining a flashlight through the grill cloth should allow you to easily see the position of the speaker so you can place your microphone accurately.
Recording in the same room as your amplifier
Recording close to your amplifier (especially with your guitar facing the amplifier) can have the benefits (especially at high gain settings) of increasing sustain and even achieving pleasant, controlled harmonic feedback. This is due to a resonant feedback loop between the amplifier, the speaker, your guitar pickups, and your guitar strings. You may also be able to achieve this effect when recording directly into the computer, if you are playing in the control room with the studio monitors (not headphones!) turned up loud enough. While it may sometimes be desirable to play guitar while separated from the amp (perhaps because the amp is in a bathroom, other separate room, or isolation box to keep it from bleeding into other instrument microphones when recording a live band), you will lose the opportunity for this particular feedback effect.
My guitar tone sounds so much brighter on the recording than it does when I listen to my amp!
Quite often (especially with combo amplifiers, where the amp and speaker are both in the same cabinet), guitarists get used to the sound of standing several feet above their speaker, while the speaker faces straight out parallel to the floor. Because of this, much of the high frequency content coming from the speaker never reaches your ears. If you start making it a habit to tilt the amp back, or put the amp up on a stand or tilted back on a chair so that the speaker is pointed more toward your head than your ankles, you will begin becoming accustomed to the true tone of your amp, which is the tone the microphone will record, and the tone that members of a live audience will hear. This may initially require you to make adjustments to your tone—but once you have achieved a tone you like with this new setup, you can be confident that the sound you dialed in will be picked up by a properly placed microphone.
Proximity effect
When a microphone with a cardioid pattern (explained later in the Large Diaphragm Condenser Microphones section of this article) is placed in very close proximity to the sound source being recorded, bass frequencies become artificially amplified. You may have heard a comedian cup his hand around the microphone with the mic almost inside his mouth to make his voice sound very deep when simulating “the voice of God” (or something like that). This is an example of the proximity effect. This effect can result in a very nice bass response when placing a microphone close to the speaker of your guitar cabinet or combo amplifier. In fact, the Shure SM57 is designed to make use of this effect as part of its inherent tonal characteristics.
On-axis vs. off-axis
You will see these terms mentioned later in my descriptions of the mic setup examples. On-axis basically means that the microphone element is pointed directly at the sound source (sound waves strike the microphone capsule at 0 degrees). Off-axis means (when mic’ing a speaker) that the microphone element is aimed at an angle rather than straight at the speaker (so the sound waves strike the microphone capsule at an angle). On-axis will give you the strongest signal, the best rejection of other sounds in the room, and a slightly brighter sound than off-axis. I usually mic my amp on-axis, with the mic (my trusty Shure SM57) somewhere near the edge of the speaker. However, this is not “the one right way.” The right way is the way that sounds best to you. I hope that the following examples will help you find your own path to the tone you are looking for.
The Shure SM57 Microphone: A Guitarist’s Trusty Friend
For recording guitar amplifiers, it is hard to find better bang-for-your-buck than the Shure SM57 dynamic microphone. It is an extremely durable microphone, and it can handle very high volume levels. When recording guitar amps, I recommend placing this mic just as close as you can to the speaker. In the following recordings, I have placed it right up against the speaker grill cloth.
I will mention that some people even simply hang the microphone so that the cable is draped over the top of the amp and the microphone hangs down in front of the speaker pointing directly at the floor. In this position, the type of floor makes a difference in the tone (wood, concrete, tile, or carpeted floors will result in different sounds), as well as the distance between the speaker, mic, and floor. This arrangement is likely to have the least amount of highs of anything discussed thus far, and will have less rejection of other sounds in the room (if you are recording in the same room as the rest of a band, this method would pick up more sound from the other instruments). I tend to avoid this method myself, but if you are short of mic stands, it could be helpful—and I would not discourage you from experimenting. It may turn out to be just the sound you were looking for.
Large Diaphragm Condenser Microphones
Room mics
Though one might often mic a room with a single microphone (perhaps a large diaphragm condenser), I have opted to use a stereo pair of small diaphragm condensers: specifically the AKG C 1000 S (an older dark gray pair). These microphones currently have a street price around $280/each USD. I attached them to a stereo mount on a single mic stand, one microphone just on top of the other, with the microphone elements arranged 90 degrees from each other (an XY pattern). This is to minimize the chance of phase problems I might otherwise encounter that could potentially cancel out some frequencies and change the tone of the recording in strange ways.
The newest way to record guitar is directly into the recorder of you choice via a 'front end' type of processor that generally 'models' the amp and cabinet with digital signal processing(DSP)
I have a BOSS VF-1 24 bit digital effects processor that includes Roland/Boss's COSM modelling algorithms, in this case I will mention the modelled Fender & Vox & Marshall guitar amplifiers plus the modelled guitar pedals like Boss's very own 'overdrive' and turbo overdrive....
I could just plug my guitar into the Hi impedance quarter inch input of the Boss VF-1 and use either the digital or analogue outputs to feed my digital recorders....but I like to combine the VF-1's digital sound with an ART tubeMP(a basic tube driven mic/instrument Preamplifier) and then into a DBX 163x compressor to smooth out rough edges, or not, and then through the Boss Loopstation before I record the tone in my digital workstations...
I have also got an alternative signal path for my guitar, where i bypass the VF-1, but process the guitar signal with the DBX compressor and the Tube preamp but then i go through an ElectroHarmonix Q-tron envelope filter, the Digitech rp-50 with casio expression pedal) and then the danelectro cool cats : metal, fuzz & drive....and finally the Boss RC-20xL Loop STation & the Recording rack ( roland cdx-1 discLab, roland vs-840 d.a.w, and the sony mds-je510 studio mini disc deck....
and that's the basic way to record your guitar either with pedals and multi-effects and/or the microphone and amplifier method.
