Finding your tone on a guitar amp takes a while. That is why people refer to great tone on a guitar as “dialed in.” It takes fine adjustments on the amp, your pedals, and your instrument over several sessions to finally find that perfect sound. Once you’ve found that sound and you’re ready to record, the last thing you’ll want is a microphone or mixing setup that doesn’t communicate that sound your amp is making clearly. This guide should help you make some smart decisions about which mic to use, where to place it, and how to recreate that sound you’ve “dialed in” to your amp.
Common Microphone Tech Specs
Before we can talk about choosing the right microphone, we’ll need to talk about what makes some mics more suited for guitars than others. In order to do that, we’ll need to explain a few things about shopping for mics. Microphones usually have the following tech specs on their packaging or description:
- Pickup Pattern (directionality)
- Dynamic Range
- Frequency Response
- Maximum Acoustic Input
Some microphones have other categories listed but I believe these are the most important to consider when shopping for a microphone. We’ll go through each of these one by one and explain what they all mean, how to make sense of the data, and how it should impact your decision.
Sensitivity is essentially exactly what it sounds like: How sensitive is this microphone? Microphone sensitivity is measured against a standard reference point of a 1 kHz tone at 94 dB SPL.
I know, you’re already a bit confused. Let’s dive a bit deeper into those terms.
“1 kHz” – The “pitch” of a sound, or its highness or lowness, is measured in hertz. Basically, this is the amount of times a sound vibration occurs per second. Higher pitches have higher hertz (Hz) while lower pitches have lower Hz. An “A” played towards the center of the piano vibrates at 440 Hz. “A” vibrating at 440 Hz is the standard by which almost all instruments are tuned, and the next “A” up on the piano will vibrate at 880 Hz, while the next “A” below will vibrate at 220 Hz. Do you see a pattern?
“dB” – This is the abbreviation for “decibel.” Decibels are a measurement of amplitude in sound waves, or in other words: Decibels measure how loud sound is. The higher the number, the louder the sound.
A microphone’s pickup pattern is a diagram that shows how sensitive a microphone is to sound coming from 360 degrees of possible directions. The most common are:
- Omnidirectional – equal sensitivity in all directions
- Bidirectional – equal sensitivity to the front and the rear, but poor sensitivity to the sides.
- Cardioid – high sensitivity towards the front and that sensitivity gradually tapers off as the source of sound drifts to the sides and eventually diminishes completely from the rear.
- Supercardioid – like a cardioid pattern, with weakened sensitivity to the sides, but moderate sensitivity to the rear.
The dynamic range of a microphone refers to how a microphone will detect sound at various volumes. The top of the dynamic range is that microphone’s maximum acoustic input. If your amp sounds best when the volume is pretty high, you’ll want to get a microphone with a high dynamic range ceiling.
The frequency response of a microphone shows how sensitive a microphone is across the spectrum of common frequencies. Typically it looks like a flat arc with even sensitivity from about 400 Hz to 6000 Hz with a slight fall-off at both ends. For some perspective:
15 Hz – The lower end of the range sound a kick drum makes
41 Hz – The low open E string on a Bass guitar
440 Hz – The open A string on a guitar
4,000 Hz – About the middle of the range of sound a Hi-Hat makes
The Best Microphones for Guitar Amps
Based on the specifications, here are my recommendations for microphones for guitar amps:
The Shure SM57 is an extremely versatile microphone. You’ll end up using this microphone for a lot more than just miking your guitar amp. It has a great frequency response for a 6 string guitar, a high dynamic range and maximum acoustic input and a cardioid pickup pattern so you can aim it right at your amp and get a comprehensive sound.
The Sennheiser e609 is pretty much only for miking guitar amps. This is the microphone you see draped over a guitar amp in studios or most live music venues that frequently host rock or blues bands. If you think you’ll be recording a lot of guitar or you can afford to have a specialty mic, this one is for you and will perform slightly better than the Shure microphone due to its higher dynamic range and maximum acoustic input.
Miking the Guitar Amplifier
So you’ve selected your microphone and you’re ready to record! Believe it or not, the first thing you’ll want to do has nothing to do with a microphone. You’ll want to decide where your amp is going to sit in the room, which way its going to face, and whether you want it on the floor or on a chair.
It is important to remember that just because the sound is coming out of the amplifier, that doesn’t mean that you don’t have to consider the echo in your room. Sound echoes off the floor as well, so elevating your amp is probably a good idea.
After you’ve selected the placement of the amp in the room with consideration to how the sound will bounce off your walls, you’re ready to start placing your mic. Remember that behind the grill of your speaker are your drivers, the parts of your amp that actually make noise. Each driver on your amp is going to be putting out almost identical sounds, so the driver you choose to mic is pretty insignificant. Each driver has three parts:
The first zone is the dust cap which is the black rounded portion at the very center of the speaker. The sound at the dust cap is full of high and bright frequencies. The white area surrounding the dust cap is the cone of the speaker. The cone has a broader and more comprehensive range of sound. Miking the cone of the speaker will give you a more accurate representation of your sound. The surrounder is the rounded edge of of the cone. Miking the surrounder will give you a sound similar to that of the dust cap.
Placing your microphone correctly will allow you to pick up an accurate representation of your guitar amp’s tone without having to do too much equalization on the mixer. If you’re having trouble seeing through your grill, most grills pop on or off easily with Velcro. Once you’ve found your desired location, you’ll want to place your microphone about an inch or two away from the grill. Remember that as your speakers drive sound, they’ll be offsetting air. The closer your microphone is to the driver, the more likely you are to pick up the “boom” of the air moving rapidly around the speaker. Also, cardioid pickup patterns have a tendency to get more ‘boom’ and sound lower the closer they are to their source.
Do not be afraid to try different locations, distances, or even angles when placing your microphone. There is no agreed upon perfect spot, you’ll want to do some test recordings with the same riff over and over again to compare and contrast the different locations, distances and angles that work best for your tone. If your tone is too low, back up the mic or aim it more towards the dust cap. If it sounds too twangy, move it closer or angle it more towards the cone.
The goal of choosing the right microphone, the right amp placement, and the right mic placement is to have an accurate representation of your tone without any equalization on the mixer. Your mixer should be right down the middle for your guitar channel. If you’ve taken everything here into consideration and experimented with all your locations and mic angles, you should be able to get a great sound on your guitar channel in your recording! Good luck!