Guitar Amp Miking 101
By Phil O'Keefe |
Guitar Amp Miking 101
Where you place the microphone can have a significant effect on the sound
by Phil O'Keefe
While it may sound like a simple task - grab a mic and point it at the amp, recording electric guitar can seem like a daunting task for the neophyte. Where is the best place to put the microphone? The answer is - "it depends".
FIRST SELECT A MIC
You have a ton of options when it comes to miking up an electric guitar amplifier, and they start with microphones; each microphone has its own individual sound and characteristics. Some microphones, such as the industry standard Shure SM57, have an upper midrange "presence peak" in the 5-7 kHz range that can help a guitar "cut through" a mix. However, it can work against you if you have a guitar that is sounding too edgy or bright. A warmer sounding ribbon microphone that lacks a presence peak may prove to be a better choice in that situation.
Moving coil dynamic microphones are often used on amps because they are low-cost, rugged and can handle high levels without caving in. However, ribbon and condenser mikes are sometimes used for their different sonic characteristics; ribbons tend to have a very warm and natural sound that captures the initial note "attack" more accurately than moving coil dynamic microphones, while condensers usually are brighter and clearer sounding.
While the SM57 dynamic is probably the single most often used microphone for guitar amplifiers, other commonly used dynamic models would include the Audix i5, the Sennheiser e609 and MD421, the Audio-Technica ATM650 and the Electro-Voice RE20. Ribbon microphones such as the Beyer M160, Royer R-121, Cascade Fathead II and AEA R92 are also commonly used. If you're looking for more sparkle and chime, a condenser such as the AKG C-414, Mojave MA-201 or Bock Audio 195 might be worth trying.
A WORD ABOUT LEVELS AND TONES
Your amp levels do not have to be raging to capture a great electric guitar sound. As long as the amp is loud enough to create a good tone, it has done its job, and all you need to do is capture it. Indeed, many classic guitar recordings were played through small, low wattage tube amps that would break up and distort at lower volume levels, so turn your amp up only as loud as it needs to go to get the tone you want.
Distortion is also tricky in the studio. Often you'll find you need less of it in the sound than you may think, so don't be afraid to experiment with lower levels of gain on your amp and stompboxes.
Dial up the sound you want to record with the guitar, effects and amp, and get it happening "in the room". If it sounds horrendous coming out of the amp, it's going to sound bad on the recording. Make sure you're happy with the way it sounds before moving forward.
Your recording levels don't have to be "slammed" either. I normally recommend setting your average signal levels at about -18 to -15dB below "0" on your meters. If your meters don't have any calibration marks, try to shoot for getting the level indicators to average near the middle of their range. You can have peaks that exceed that level occasionally, but you should try to avoid running "into the red" and clipping your recording.
HIGH PASS FILTERS
If your microphone or preamp has a high pass filter, you may want to record with it engaged to help filter out the subsonic gunk that doesn't contribute to the guitar sound, but can cloud the bottom end of your mixes. Such filters are fairly common on condenser microphones, but rare with ribbon and moving coil dynamic mikes, so I normally use a high pass filter plugin set to around 80-100Hz on electric guitar tracks when I mix to accomplish the same thing. Experiment to see what sounds best in your situation.
WHERE IS THE SPEAKER?
Some amps have grille cloths that are fairly transparent, and it's easy to see where the speaker is. Other grilles are far more opaque, and spotting the speaker can be trickier. (Fig. 1) Sometimes shining a flashlight through the grille cloth will help, or looking through the grille up close or from an angle will allow you to see where the speaker is located. Some amps have removable grilles, and pulling the grille off can offer you better access to the speaker - but be careful! The grille is there to protect the speaker from damage, so use caution whenever the grille is removed.
On some amps, you will have multiple speakers to choose from. Usually it is a good idea to experiment with placing the mic on each, and listening to determine which one sounds the best. Even with a 4X12 cabinet that has four supposedly identical speakers in it, it is not uncommon to find one that sounds noticeably better than the others.
THE HORIZONTAL LINE
Positioning the mic in different locations can allow you to change the basic sound with no adjustment to the amp, and without changing microphones. To demonstrate this, we're going to be working across an imaginary horizontal line that runs straight across your speaker at its widest point, and directly through the center; from the outer side edges of your speaker, called the surround, and through the cover in the middle of, and over the center of the speaker, which is called the dust cap. Moving the microphone sideways across this horizontal line will have a dramatic effect on the sound. If you point it directly at the center of the cone - straight at the dust cap, you will get the brightest sound. Clip 1 was recorded with the microphone in this location. (Fig. 2)
For quick reference, Clip 5 contains the audio from Clips 1-4, one after the other and without the spoken word descriptions, for easier comparisons. As you can hear, the further away from the center of the speaker you aim the microphone, the darker the sound will be, and the closer to the center of the speaker you position it, the brighter and more articulate it will sound.
ON AND OFF-AXIS
You'll sometimes hear the terms "on-axis" and "off-axis" applied to microphone positioning. On-axis simply means in the same direction as the speaker "fires"; on guitar speaker cabinets, pointing the microphone straight in and directly at the speaker (90 degree angle, relative to the grille cloth) will normally be "on-axis", while angling the microphone so that it is at a 45 degree angle relative to the grille cloth would normally be "off-axis". While on-axis placement is common, don't overlook the different sounds that slightly off-axis placements can provide. For example, in Clip 4, the microphone is placed all the way out by the side edge of the speaker, but angled in 45 degrees so that it is aimed towards the center dust cap. (Fig. 5) This provides some of the advantages of both positions - the brightness of the center position and the warmth of the edge of the speaker position.
DISTANCE EQUALS DEPTH
While putting the mic within an inch or two of the grille cloth is the most common technique, don't be afraid to experiment with more distant microphone placements. Clip 6 demonstrates the sound of the microphone when it is positioned 8 inches away from the grille, (Fig. 6) and contrasts that with the sound of Clip 1, where the mic was aimed at the exact same spot, but was positioned much closer; only about an inch away from the grille cloth. (Fig. 7) As you move the microphone further away from the speaker, it begins to capture more ambience, room reflections and reverb. This can help you achieve a sense of "depth" to your recordings. Be careful with this though - once it's captured as part of the recording, it will be impossible to "remove" that ambience later. If you have enough microphones, you can use two microphones; positioning one mic in close, with a second mic further from the amp - sometimes this second mic can be several feet away, depending on the sound of the room and your preferences. Record each mic to a separate track so that you can blend them to taste at mixdown.
RECORDING CHAIN AND FINISHING UP
Where you position the mic is ultimately up to you, but the basics are pretty simple. Just remember - closer to the center of the speaker equals a brighter sound, and closer to the edge of the speaker gives you a darker tone. Moving the mic closer to the speaker provides a drier, more "immediate" sound with greater low frequency emphasis due to proximity effect, while more distant placements will give you a more ambient sounding track that sounds as if it is coming from "further away" from the listener. The important thing to remember is to get the sound happening in the room, and then if it doesn't sound good on the recording, try a different microphone or move the mic until you find a "sweet spot" where what you hear is what you're after.
The recording chain used on these clips was fairly straightforward. The guitar was a '75 Fender Duo Sonic with Abagail Ybarra wound Strat pickups. The bridge pickup was used by itself for all clips. The amp is a "blackfaced" '71 Fender Princeton Amp with a reissue Jensen C10R speaker. The volume, bass and treble controls were all set at 5. The microphone used was a Beyer M160 ribbon, and it was running straight into an API 312 mic preamp. No compression or EQ was used while tracking, although a 6dB per octave high pass filter set at 100Hz was used to reduce excessive low frequencies in the mix for all of the clips. -HC-
Phil O'Keefe is a multi-instrumentalist, recording engineer / producer and the Senior Editor of Harmony Central. He has engineered, produced and performed on countless recording sessions in a diverse range of styles, with artists such as Alien Ant Farm, Jules Day, Voodoo Glow Skulls, John McGill, Michael Knott and Alexa's Wish. He is a former featured monthly columnist for EQ magazine, and his articles and product reviews have also appeared in Keyboard, Electronic Musician and Guitar Player magazines.