Virtual Miking with Amp Sims

The virtual mics and room options included with amp sims can have a major effect on the sound

By Craig Anderton

A physical guitar amp is more than a box with a speaker—it’s a box with a speaker being picked up by a mic in a room, and both the mic and room make a major contribution to the overall sound. To better emulate the sound of a “real” guitar amp, many amp sims include ways to emulate mic position, mic type, and often, the amp’s position in the room or the ability to add “air.”

The following images illustrate the options available in several popular amp sims; note that these are not in-depth reviews, but quick sketches of the types of features that are available. Because you can usually add or construct room sounds with other plug-ins, but simulating different mic types and positions is more complicated., most amp sims tend to put most of their efforts into the miking options.

Finally, note that amp cabinets based on impulse responses usually don’t let you play around with mics, because that’s typically part of the impulse response.

Choosing Cab in Line 6 POD Farm’s "Amp" view brings up a way to place the selected cabinet in a virtual room and specify the amount of room sound, as well as choose from four mic types with different positions (57 on axis, 57 off axis, 421 dynamic, and 67 condenser).

Waves’ G|T|R offers 12 mics with various positions in a single drop-down menu; with some amps, an additional delay control simulates space.

For Scuffham’s S-Gear 2’s cabinets, there are two mic choices (ribbon and dynamic), each with four placements with respect to the speaker. While not option-laden, the sound quality is very satisfying.

With Overloud’s TH2, there are four mics. Two of these offer 18 different mic types, with controls for horizontal and vertical positions with respect to the speaker cabinet, distance from the cone, and phase, The two additional mics don't have these various adjustments; instead, one is rotated 45 degrees and placed in front of the speaker, while the other aims toward the back of the cabinet. All four mics go to a dedicated mixer module (peeking out toward the top, below the navigation section). There are also five different kinds of ambience.

Native Instruments’ Guitar Rig includes Control Room Pro, a module with eight independent sections. You can load any of 29 different cabinets as well as DI and no cabinet (23 cabs offer three different mic placements on the speaker cone), and five different mics. There are also controls for level, pan, phase, and room amount for each section; a master mixer duplicates the section pan and level controls, but also includes master bass, treble, and air controls.

IK Multimedia’s AmpliTube 3 has two cab positions in a stereo routing, where you can load a huge number of different cabinets. Mic-wise, you can place two mics (chosen from a wide variety) on each cab, move their positions around with respect to the speaker cone, flip phase on either one, and crossfade between the two. For ambience, there are two additional room mics have variable width (physical separation), and the pair can be panned—handy if you’re running two cabs in stereo. (I didn’t give an exact number of cabs and mics because I’ve customized the roster via IK’s “Custom Shop.”

Peavey’s ReValver offers 5 different mics but with 20 different total options (e.g., some represent different polar patterns, others include low frequency cuts). But in terms of creating ambience, the main aspect of interest is that you can specify the distance from the speaker, distance from the cone, and the angle between two virtual mics when running in stereo.

Softube’s Vintage Amp Room has a mic for each of the three amps you can move closer or further away from the amp, as well as move off-axis in the closest position. Note that only one amp is available at a time. Their Metal Room has two amps, but the miking is more sophisticated—two mics on each where you can vary distance, angle at the closest position, crossfade, and stereo width.

CHOOSING THE MIC TYPE

So which mic and position is optimum? Let your ears be the judge, but here are some guidelines to get you started. Let’s look at mics first.

• Dynamic mic: This is a common miking choice for amps, with a relatively balanced response and solid lows. Dynamic mics work well for powerful sounds where you want to avoid “brittleness.”
• Condenser mic: These are generally brighter (like the difference between a single-coil and humbucker pickup). Use this when you want definition, or more clarity from clean sounds.
• Ribbon mic: The ribbon mic family typically gives the warmest (or darkest, depending on your viewpont) sound. Thre’s often a lower midrange emphasis that gives a “creamy” tone.

With programs that let you choose multiple mics, it’s common to use condenser mics for room sounds as the highs tend to drop off naturally within a room.

MIC POSITIONING

More amp sims are including the option to have cab mics and room mics. The two main cab options are on- or off-axis.

• On-axis: The mic points at the virtual speakers, which gives the fullest sound and smoothest midrange.
• Off-axis: The mic points at the speakers from an angle; this introduces peaks and valleys in the midrange, while thinning out the low and high ends a bit.

As to ambience or “air,” consider leaving it off for live performance as the room you play in will impart its own sonic characteristics (whether you want it to or not!). For recording, avoid adding ambience until other tracks have been cut. More ambience can make the guitar sit “further back” in the mix at low levels, or take over the stereo field at higher levels. I tend to use minimal ambience with rhythm guitar so the sound is more defined, but leads often benefit from some “air.” Of course, stacking two or more amps, with their own ambience and miking, opens up a whole other bunch of tone tinkering options. And isn’t that what amp sims are all about?

  Craig Anderton is Editor Emeritus of Harmony Central. He has played on, mixed, or produced over 20 major label releases (as well as mastered over a hundred tracks for various musicians), and written over a thousand articles for magazines like Guitar Player, Keyboard, Sound on Sound (UK), and Sound + Recording (Germany). He has also lectured on technology and the arts in 38 states, 10 countries, and three languages.