Using Multiple Mics on Guitar Amps

Single microphone recordings capture guitar amplifiers effectively, but multiple microphones expand tonal possibilities dramatically. Different microphone types emphasize different frequency ranges and characteristics. Combining them thoughtfully creates guitar sounds that no single microphone achieves alone.

Why Use Multiple Microphones

Each microphone type has inherent strengths and limitations. Dynamic microphones like the SM57 capture focused midrange but lack extended high and low frequencies. Ribbon microphones provide smooth top end but may need reinforcement in the upper midrange. Condensers offer detail but can sound harsh on distorted signals.

Combining microphones allows capturing the best qualities of each. The SM57’s punch combined with a ribbon’s smoothness creates a complete frequency picture. Adding a room microphone introduces depth and dimension. The result sounds larger and more three-dimensional than any single microphone.

Multiple microphones provide mixing flexibility. Individual microphones can be processed separately—one might receive compression while another stays dynamic. Balancing the blend during mixing tailors the tone to fit specific arrangements. Changing the balance transforms the sound without re-recording.

Classic Microphone Combinations

The SM57 and Royer R-121 pairing has become a modern standard. The SM57 provides aggressive midrange presence and transient detail. The R-121 adds warmth, extended low end, and smooth high frequencies. Placed identically at the same speaker, these microphones complement each other naturally.

Dynamic and large-diaphragm condenser combinations capture full frequency range. The dynamic microphone handles close placement and high SPL, while the condenser, positioned slightly farther, adds air and detail. AKG C414, Neumann U87, or similar microphones work well in this role.

Two dynamic microphones at different positions create phase-based tonal options. An SM57 on the cap and another at the cone edge produce different tones. Blending them or selecting one versus the other provides flexibility. Phase alignment becomes critical with this approach.

Phase Alignment Techniques

Phase problems occur when microphones receive sound at different times. The time difference causes certain frequencies to cancel when signals combine. The result sounds thin, hollow, or lacks impact. Proper alignment prevents these issues.

Physical measurement ensures equal distance from the sound source. A tape measure or string confirms both microphones sit equidistant from the speaker cone. Even small differences—fractions of an inch—can cause audible phase problems at high frequencies.

The zoom and null technique uses headphones for fine adjustment. Sum both microphones to mono and listen while slowly moving one. The position with the fullest low end and clearest tone indicates optimal alignment. Alternatively, find the thinnest sound and move the microphone slightly past that point.

Polarity flip testing reveals phase relationships. With microphones blended and summed to mono, flip the polarity of one microphone. Choose whichever polarity produces the fullest sound. If both options sound problematic, physical repositioning is necessary.

Close and Room Microphone Combinations

Room microphones capture the amplifier’s interaction with the acoustic space. Placed several feet from the cabinet, they record reflections and ambience. This distant perspective adds depth impossible to achieve with close microphones alone.

Balance between close and room determines the spatial quality. Heavy room microphone levels create a live, spacious sound. Minimal room creates a tight, present tone. Most recordings use room microphones subtly, adding dimension without washing out definition.

Room microphone selection favors condensers for their extended frequency response. Large or small diaphragm condensers both work well. Omnidirectional patterns capture the most room sound, while cardioid patterns provide more direct sound with some room character.

Practical Setup Considerations

Gain staging each microphone independently optimizes signal quality. Close microphones facing loud amplifiers need less preamp gain than distant room microphones. Setting each channel’s gain for optimal level ensures clean recordings across all microphones.

Monitoring during recording benefits from hearing the intended blend. Setting up a rough mix with all microphones lets the performer hear the combined sound. This approach helps identify problems during recording rather than mixing.

Documentation of microphone positions enables recall for overdubs or future sessions. Photos of placement, notes about distance and angle, and rough mix settings all help recreate successful tones. Building a library of documented setups accelerates future sessions.

Creative Multi-Mic Applications

Different cabinets fed by the same amplifier create unique textures. A 4x12 and 1x12 receiving the same signal produce distinct tones. Combining microphones on both cabinets yields complex sounds impossible from any single speaker.

Stereo miking of a single speaker uses two microphones at different positions. Panned apart, they create width from a mono source. The different tonal qualities of each position add interest. Phase alignment remains important for mono compatibility.

Intentional phase manipulation creates unusual textures. Slightly misaligning microphones produces comb filtering with a distinctive sound. This technique works for specific applications where the unusual character suits the music. Most conventional recording avoids this effect.