Get That Guitar!

Feb 1, 2011 9:00 AM, By Pete Keppler



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Pete Keppler

Pete Keppler

The sheer number of different amps, amp simulators, direct-input systems and acoustic pickups on the market today for guitar is pretty staggering—probably not that far from the number of musicians who are out there actually plugging into it all. In the world of guitar amps alone, dozens of boutique companies have sprung up in the past 10 to 20 years, not to mention the major manufacturers that keep cranking out new models every year and bringing out various re-issues of their classic amps from the 1950s, ’60s and ’70s. With so much gear out there, the quest for a killer guitar tone in your live mix may seem a little daunting. It will take a bit of experimentation, but assuming your player has settled on a rig that they’re comfortable with onstage, it’s relatively easy to zero in on your options and make a choice for the best method of capturing that sound.

When selecting mics for a guitar amp, a good first step is just to listen. Because much of the sound from any non-synthetic instrument is shaped by the player’s style and technique, try to get the actual player (not their tech or other substitute) to play through the entire rig, including wireless systems, pedals and all lengths of cable being used. Make a mental note of the overall sound of the rig, whether it seems balanced, overly bright or dark, thin, muddy, etc., and base your initial choice for a mic and its placement on that. The number of instrument mics on the market is growing, too, thankfully more slowly than the inventory of amps! My usual palette includes the Shure SM57, SM7, Beta 98 and KSM 32; Sennheiser 421 and 609 (or 409 if you can find one); Audio-Technica 4050 and 2500; Electro-Voice RE-20; and the Royer 121. These mics all have their own unique character when placed close-up on a speaker. In general, the larger-diaphragm mics will have a fatter sound, but in the case of the larger condenser mics, they may also have a brighter, extended top end. Still, four out of five engineers agree: The 57 is always a good (and inexpensive) place to start.

Most engineers believe the best placement for a mic close-up on the speaker cone is off-center. Find the center of the speaker (use a flashlight if you can’t see directly through the grille cloth) as a starting point and set the mic about halfway between that point and the edge of the cone. Keep in mind that the higher, harsher frequencies tend to emanate from the center and the lower, fatter frequencies from the edge. How far away you place the mic from the speaker will also have a significant effect on the tone: The closer you are, the more low end you’ll pick up due to most mics’ proximity effect. In live situations, you don’t usually have the luxury of more distant miking, but even the difference of moving the mic a few inches out can produce a very audible change. Another way to make a difference at the source (often the best place to make a correction) is to angle the mic with regard to the axis of the speaker. Assuming your speaker is facing out horizontally and the mic facing it directly, try angling the mic about 45 degrees toward the floor. This will often calm harsher tones a little without changing the overall sound. In the case of ribbon mics, the 45-degree angle is often recommended by their manufacturers to avoid stretching or breaking the ribbon—a costly repair. Ribbon mics, while often significantly more expensive, tend to give you the most honest rendition of what’s actually happening at the speaker, if that’s what you’re after. They are more delicate though, and don’t take well to rough handling.

Note: A situation that I’ve run across concerning more recent “boutique” amps is that some manufacturers and custom builders have found that installing two types of speakers in their combo amps or speaker cabs will give them a unique sound. Quite often, the two speakers will have significant sonic differences and you may find that one is more “mic friendly” than the other.

Another technique is to use two mics (or more if there are multiple amps and speakers); a dynamic and a condenser usually make a good combo. If you want to try this and you’re on a tighter budget, or don’t have access to the more expensive condensers, try using an SM57 and the Sennheiser 609. The key here is to make sure that the mic diaphragms, not just the grilles, are the same distance from the speaker cone—the reason being, a difference in distance will cause problems with time alignment, which may come in the form of decreased high frequencies and comb-filtering. An easy way to check for this is to set your mics at equal gain at the console, set the channel EQs flat and bring the first mic up for a listen. (For this process, I usually pan all the mics to one side of the P.A. or listen in headphones.) Then add in the other mic to an equal level and listen for any anomalies.

If the sound gets louder without any loss of frequency response, you’re in good shape. If the volume gets lower or the tone thins out substantially, check your phase buttons on the console’s mic inputs. If that doesn’t correct the problem, head back up to the stage and see if someone’s kicked your mics out of place or there’s a blown or out-of-phase speaker. (See the “Idiot Check” sidebar.) The Audio-Technica AE2500 mentioned earlier was originally designed to be a bass drum mic, but is becoming a favorite for guitar amps. It has two discrete mic capsules in one body: one dynamic and one condenser. And because they’re in the same body, they’re perfectly time-aligned, which is an added benefit. Audio-Technica provides a special cable that terminates in dual XLR connectors to plug into the console, one for each capsule. Plug them in, blend as you like and you’re good to go—quick and easy.

I’ve dealt with some thin-sounding open-backed speakers and combo amps (or a player that puts an amp on the floor, cranks the midrange and treble controls, and tells you, “That’s my tone,” even though they can’t hear all the nasty high frequencies aimed at their knees). A great solution for this situation is another two-mic method: front and rear. Just remember to phase-reverse the rear mic and try to keep the distances equal between the mics and the speaker. The rear mic will give you more bottom and less of the harsh overtones than the front mic.

An important factor when using multiple mics on a rig, especially on tour, is consistent placement. Mics on stands are easily bumped and moved, wrecking the time alignment and phase you worked so hard for. I’ve seen and used several semi-permanent mounting systems that work well. The LP Claw can often be used to mount a mic securely from the side of a cabinet, and there are many systems from Atlas, Audix, On-Stage and Z-Bar that also work well. The added bonus is that if the cabinet gets moved (intentionally or otherwise), the mics stay put, saving you from running to the stage to reset them (or fishing a union stagehand out of the break room to do it, depending on the city you’re in). For consistency’s sake, it’s also a good idea to mark your mic placement on the speaker grille with a thin strip or two of gaff tape.

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