How to Mic a Guitar Amp — Complete Recording Guide

Recording electric guitar through a microphone placed in front of an amplifier is the technique used on the majority of recorded rock, blues, country, and metal guitar tracks in history. Understanding how to position a microphone, choose the right technique, and adapt to different rooms significantly affects the quality of your guitar recordings.

This guide covers microphone selection, placement techniques, single and dual mic setups, and how to handle the acoustic environment.

The Fundamentals: Why Mic Placement Matters

A guitar amplifier's speaker does not radiate sound uniformly. Different positions in front of the cone produce meaningfully different tonality:

• Dead centre (on-axis): The speaker's highest-frequency energy is concentrated at the centre of the cone. On-axis placement captures the full high-frequency character — bright, detailed, and sometimes harsh at high gains.
• Edge of cone (far off-axis): The edge of the cone radiates more low-frequency and mid-frequency energy with reduced high-frequency content. Edge placement produces a warmer, darker tone.
• Between centre and edge: The standard position for most recorded guitar. Allows adjustment between brightness and warmth by moving the microphone.

Distance from the speaker:

• Close (1–5cm from grille): Captures the direct speaker sound with minimal room ambience. Maximum presence and clarity.
• Further away (30cm–1m): Includes increasing amounts of room ambience. Adds space and natural reverb but reduces direct sound clarity.
• Room position (2–4m): Captures predominantly room sound — useful for ambient guitars, less useful for close-miked rock guitar.

The Microphone: Shure SM57

The Shure SM57 is the industry-standard guitar amplifier microphone. It appears on nearly every professionally recorded guitar track in the last 40 years and is used in professional studios worldwide.

Why the SM57:

• High SPL handling: Guitar amplifiers are loud. The SM57 can handle extremely high sound pressure levels without distorting — important when miking close to a loud amplifier
• Frequency response: The SM57's response is not flat — it has a presence peak (boost in the 5–10 kHz region) that adds clarity and definition to guitar recordings. This is not a flaw; it is a feature that complements guitar
• Cardioid polar pattern: Captures sound from the front and rejects sound from the sides and rear, minimising room pickup
• Durability: The SM57 is extremely rugged
• Price: Around £100 — modest for a professional studio tool used on half the records ever made

Alternatives:

• Sennheiser MD421 (around £300): More low-end capture than the SM57; used alongside SM57 in dual-mic setups for warmth
• Shure SM7B (around £350): Broadcast dynamic microphone with a flatter response; used for guitar in some contexts
• Audix i5 (around £80): Similar character to SM57, slightly warmer, good value alternative
• Ribbon microphones (Royer R-121, around £1,400): Extremely detailed, warm, fragile — professional studio choice for additional warmth and dimension

Standard Single Mic Technique: The SM57

Step-by-Step Setup

1. Position the amplifier in the recording space. Placing it on the floor can add low-end pickup from floor reflection; elevating it on a stand reduces floor coupling and positions the speaker at a better working height.

2. Identify the speaker cone. If the cabinet has a grille cloth, feel through the cloth to identify the speaker's centre. Most cabinets centre the speaker(s) within the cabinet.

3. Choose your starting position. For a balanced starting tone: SM57 aimed at a point halfway between the centre and edge of the cone, capsule 2–3cm from the grille cloth.

4. Connect the SM57 to your audio interface via XLR cable. Engage phantom power if required — the SM57 does not require phantom power (it is a dynamic microphone), but it does not harm it.

5. Record a test phrase and listen back through headphones or monitors.

6. Adjust position to taste:

   • Too bright/harsh: Move the microphone away from the centre (toward the edge) or increase the distance slightly
   • Too dark/muddy: Move the microphone toward the centre
   • Too much room sound: Move closer to the grille
   • Too dry: Move further back

The Angle Matters Too

Most engineers angle the SM57 slightly rather than pointing it directly at the cone (perpendicular to the grille). A slight angle of 15–30 degrees from perpendicular can soften the high-frequency character and produce a rounder, less aggressive tone. Experiment with angle in combination with cone position.

Dual Microphone Techniques

Using two microphones simultaneously provides blending flexibility and can capture the full frequency range of the amplifier more effectively than a single microphone.

SM57 + Sennheiser MD421

The most classic dual-mic combination for guitar. The SM57 captures the high-frequency detail and presence; the MD421 captures more low-frequency weight and warmth.

Placement:

• SM57: Halfway between centre and edge, 2–3cm from grille, standard SM57 position
• MD421: Slightly further from the grille (5–10cm) and aimed at a similar cone position, or aimed at a slightly different position for a different frequency balance

Mixing: Record both microphones on separate tracks. In the mix, blend them at different levels — more SM57 for brightness, more MD421 for warmth. A common starting point is 60% SM57, 40% MD421.

Phase alignment: When using two microphones, check phase alignment. If both microphones are at different distances from the speaker, there will be a slight time delay between them. When mixed together, this can cause phase cancellation (certain frequencies cancel, producing a thin sound). Solutions: physically adjust one microphone until both are equidistant from the speaker, or use the "Flip Phase" function on one track in your DAW.

SM57 + Room Microphone

The room microphone captures the natural ambience of the recording space alongside the close-miked direct sound.

Placement:

• SM57: Close position (standard technique)
• Room mic: 1–3m from the amplifier, aimed at the amplifier. A large-diaphragm condenser (like the Audio-Technica AT2020, around £80) or an omni-directional microphone captures room ambience well

Using the room track: In the mix, blend a small amount of the room signal under the close-miked SM57 signal. This adds natural space and dimension without the obviously artificial quality of a reverb plugin. Start with the room microphone at -6 to -12dB relative to the SM57 level.

Room acoustics: The quality of the room microphone signal depends entirely on the acoustic quality of the room. A bedroom with soft furnishings captures different ambience from a large tiled bathroom. Experiment — some rooms produce beautiful natural reverb; others should be used only as close-miked references.

Handling Room Acoustics in Home Studios

Most home studio spaces are not acoustically treated and introduce unwanted reflections, flutter echoes, and resonances into guitar recordings.

The Problem

Sound from the amplifier reflects off parallel walls, floors, and ceilings. These reflections arrive at the microphone later than the direct sound, causing:

• Comb filtering (frequency cancellations and enhancements at specific frequencies)
• Flutter echo (a rapid repetitive echo in live, reflective rooms)
• Room boom (low-frequency resonance in small rooms)

Basic Solutions

Close-miking minimises room influence. An SM57 at 2–3cm from the grille captures predominantly direct speaker sound. Room reflections are audible but not dominant.

Absorption around the amplifier: Placing moving blankets, duvets, or foam panels around the amplifier (leaving the front open for microphone access) reduces reflections from adjacent surfaces.

Recording in a wardrobe or closet: A wardrobe full of clothing is an excellent natural sound absorber. Recording with the amp in a wardrobe (door partially closed, microphone inside) is a genuinely effective low-cost solution.

Isolation boxes: Commercial guitar cab isolation boxes (Harley Benton's amp cab isolator, around £80; GruvGear Guitar Amp Wedge) are enclosures that surround the amplifier and dramatically reduce room leakage.

Gain Staging and Levels

Setting Record Levels

When recording guitar amplifier through a microphone:

1. Set the preamp gain on your audio interface to achieve peaks around -12 to -6dBFS (digital full scale). Higher than -6dBFS risks digital clipping; lower than -18dBFS wastes dynamic range.

2. Do not use excessive gain. A loud amplifier close to a microphone produces significant signal level — your interface's gain control may need to be at minimum to avoid clipping.

3. Check with your loudest sounds. Set gain while playing the loudest, most dynamic moment in what you are recording. The gain should be set so even those peaks do not clip.

Monitoring While Recording

• Use headphones to monitor while recording if possible, to avoid picking up monitor speaker sound
• Do not monitor at high volume through the same speakers in the room as you are recording — monitor bleed into the microphone is a significant issue in small rooms
• Direct monitoring (listening to the input signal from the interface) adds no latency; software monitoring may have noticeable latency depending on buffer settings

Direct Recording (DI) as an Alternative

Recording guitar direct-in (DI) — connecting the guitar directly to the audio interface without a microphone or amplifier — is a valid and increasingly popular approach.

With amp simulation software: Neural DSP (Archetype Nolly, Parallax), Positive Grid BIAS Amp 2, Line 6 Helix Native, or the amp simulation in Logic Pro/GarageBand provide guitar amplifier emulations that can be excellent.

Advantages of DI:

• No noise or bleed issues
• Infinitely re-adjustable after recording (process the DI with different amp sims until the sound is right)
• No microphone or room concerns

Disadvantages:

• The character of a real amplifier through a real microphone in a real room is still different from software emulation
• Requires software (often paid) to achieve convincing results

Many professional recordings use a combination: a miked amplifier alongside a DI signal, allowing the best of both in mixing.

Frequently Asked Questions

What is the best microphone for recording guitar amp? The Shure SM57 (around £100) is the industry standard and appears on the majority of professional rock guitar recordings. For a second microphone in a dual-mic setup, the Sennheiser MD421 (around £300) or a large-diaphragm condenser like the Audio-Technica AT2020 (around £80) are common choices.

Where do I place the SM57 on the speaker? A useful starting position: halfway between the centre and the edge of the speaker cone, with the microphone capsule 2–3cm from the grille cloth. Move toward the centre for more brightness; move toward the edge for more warmth.

Do I need a specific room to record guitar? A treated room is ideal but not required. Close-miking (SM57 very close to the grille) minimises room influence. A bedroom with soft furnishings, carpets, and fabric will produce better results than a live, reflective tiled room.

Can I record guitar amp in an apartment? Yes, but carefully. Guitar amplifiers can be loud enough to disturb neighbours. Solutions: low-wattage amplifiers (5–20 watts) played at moderate volume, an isolation box, a load box with DI output (Boss Waza Tube Expander, Two Notes Torpedo), or amp simulation software for silent recording.

What is the difference between on-axis and off-axis microphone placement? On-axis means the microphone is aimed directly at the centre of the speaker cone. This captures maximum high-frequency content, producing a brighter tone. Off-axis means the microphone is aimed away from the cone centre (toward the edge or angled away). Off-axis produces a warmer, darker tone with less high-frequency content.

Should I use condenser or dynamic microphone for guitar amp? Dynamic microphones (SM57) are the primary choice — they handle high SPL well and have a frequency response well-suited to guitar. Large-diaphragm condensers can be used as room microphones (placed further back) but are generally too sensitive for close-miking loud amplifiers.