A Comprehensive Guide on How to Mic a Guitar Amp

As a guitarist, achieving the perfect tone is a never-ending pursuit, and one of the key elements in capturing that sweet sound is properly miking your guitar amplifier. Whether you’re recording in the studio or performing live, understanding the art of microphone placement and selection can make a world of difference in the final output. In this blog post, I will delve into the essential techniques and tips of how to mic a guitar amp, helping you unlock the full potential of your instrument.

Table of Contents

Choosing the Right Microphone

Dynamic Microphones

Dynamic microphones are rugged and reliable, making them perfect workhorses for miking guitar amps in various scenarios. Their ability to handle high sound pressure levels (SPL) without distortion allows them to capture the powerful and intense output of guitar amplifiers. The Shure SM57 is a legendary choice among sound engineers and musicians alike for miking guitar amps. Its iconic presence in studios and on stages worldwide is a testament to its sonic qualities. The SM57 is especially popular for recording electric guitar cabinets. It can emphasize the punch and character of the amp while providing a balanced representation of the instrument’s tone.

Condenser Microphones

Condenser microphones are known for their sensitivity and ability to capture even the most delicate nuances of sound. When miking a guitar amp in the studio, condenser microphones like the AKG C414 are a go-to choice. The C414 offers multiple polar patterns, enabling the engineer to tailor the microphone’s directionality to the specific needs of the recording. By using a cardioid pattern, the microphone focuses on the amp. Using an omnidirectional pattern captures more of the surrounding room ambiance. This versatility allows the engineer to achieve different sonic textures. This makes condenser microphones invaluable tools in the quest for the perfect guitar tone.

Positioning the Microphone

On-Axis

Placing the microphone on-axis, directly in front of the guitar amp’s speaker cone, is a classic miking technique for capturing an accurate representation of the amp’s sound. By positioning the microphone perpendicular to the center of the speaker cone, you capture the most balanced frequency response. This technique is especially effective for recording clean tones or when you want the true essence of your guitar amp to shine through without added coloration.

Off-Axis

Moving the microphone slightly off-center from the speaker cone alters the frequency response, emphasizing different tonal characteristics. By angling the microphone away from the center, you can tame harsh or bright tones. The degree of off-axis positioning will impact the degree of frequency attenuation, so subtle adjustments can make a significant difference in the overall sound. This technique is particularly useful for handling overly bright or aggressive amps without sacrificing their inherent character.

Edge of Cone

Positioning the microphone near the edge of the speaker cone captures a brighter and more aggressive sound. The speaker cone’s edge tends to produce sharper transients and higher frequencies, resulting in a more “bitey” tone. This technique is commonly employed in rock and metal genres, where a cutting and aggressive guitar sound is often desired. However, be cautious not to place the microphone too close to the edge, as it may introduce harshness or distortion.

Distance from the Amp

Close-Miking

Close-miking involves placing the microphone within a few inches from the amp’s grill cloth. This proximity captures the immediate presence of the amp’s sound and results in a more focused and intense tone. Close-miking is beneficial for capturing the amp’s natural compression and capturing more of the speaker’s direct sound, making it ideal for recording distorted or overdriven tones. Additionally, close-miking helps isolate the guitar amp from other sound sources in a live performance, reducing the likelihood of bleeding from other instruments.

Room-Miking

Room-miking is about placing the microphone at a distance from the amp, allowing it to capture not only the direct sound from the speaker but also the acoustic qualities of the surrounding room. This technique is more prevalent in studio recordings, where engineers seek to capture the amp’s sound in a more natural and open environment. The room’s acoustic characteristics influence the tone, and the reflections and reverb of the space add a sense of depth and spaciousness to the recorded sound. Experiment with different room sizes and microphone placements to achieve the desired amount of room ambiance in the recording.

Phase Considerations

When using multiple microphones to capture the same guitar amp, phase relationships become critical. Phase cancellation occurs when two or more microphones pick up the same sound source but are out of phase with each other. As a result, certain frequencies may cancel each other out, leading to a thin or hollow sound. To avoid phase issues:

Use the “3-to-1 Rule”

The “3-to-1 Rule” states that the distance between each microphone should be at least three times the distance from each microphone to the sound source. Let’s break down what this means in practice:

Distance from Sound Source: For each microphone being used, measure the distance from its position to the sound source. In the context of miking a guitar amp, this would typically be the distance from the microphone to the speaker cone.
Distance between Microphones: Next, measure the distance between each microphone being used. This is the distance between the centers of the microphones.
Apply the “3-to-1 Rule”: To adhere to the “3-to-1 Rule,” ensure that the distance between each microphone is at least three times the distance from each microphone to the sound source.

For example, if you are using two microphones to capture a guitar amp and each microphone is placed 6 inches away from the speaker cone, the distance between the two microphones should be at least 18 inches (3 times 6 inches). This ensures that there is enough physical space between the microphones to reduce the chance of phase cancellation.

Why the “3-to-1 Rule”

Why is the “3-to-1 Rule” Important? Adhering to the “3-to-1 Rule” helps avoid phase issues and preserves the integrity of the sound being captured. When microphones are spaced too closely together, they can pick up similar sound waves at slightly different times, leading to phase discrepancies. This misalignment can cause certain frequencies to cancel each other out, resulting in a loss of tonal richness and clarity.

By adhering to the “3-to-1 Rule,” you minimize the chances of phase cancellation between the microphones, allowing them to capture distinct aspects of the sound source accurately. This is particularly important when using multiple microphones on a single instrument, such as miking a guitar amp with both a dynamic and a condenser microphone.

Guideline, Not a Rule

It’s worth noting that while the “3-to-1 Rule” is a helpful guideline, it’s not a hard-and-fast rule. In some situations, engineers may intentionally use mic placement to create phase relationships for creative purposes. However, when aiming for a natural and balanced sound, following the “3-to-1 Rule” is generally a safe approach.

In conclusion, the “3-to-1 Rule” is a valuable tool to keep in mind when using multiple microphones on a single sound source like a guitar amp. By spacing the microphones appropriately, you can achieve a more cohesive and accurate representation of the sound, minimizing phase issues and obtaining a higher-quality recording or live sound.

Check Phase Alignment

To ensure proper phase alignment, listen to the combined output of the microphones. If you notice any thinning or hollowing of the sound, try reversing the phase (polarity) of one of the microphones and compare the results. Keep adjusting until you achieve the fullest sound without phase-related problems.

Blending Microphones

Combining different microphone types can offer a more dynamic and multi-dimensional guitar tone. For instance, using a dynamic microphone and a condenser microphone together can provide a balance of warmth and clarity. Here are some blending ideas:

Use the Shure SM57 for close-miking to capture the immediate presence and punch of the amp’s sound.
Pair the SM57 with a condenser microphone like the AKG C414 placed further away to capture the room ambiance and add depth to the sound.
Adjust the relative levels of each microphone to achieve the desired balance. In the mix, you can further fine-tune the blend to get the perfect guitar tone that fits well with the other instruments.

Experimentation and Trusting Your Ears

Miking a guitar amp is an art that combines technical knowledge with intuition. There are no rigid rules, and every setup may require different approaches. As you experiment with different microphone types, positions, and distances, always trust your ears as your ultimate guide. Be patient and open to trying new techniques. Small adjustments can make a significant impact on the final tone. Listening critically and making informed decisions based on what you hear will lead you to discover the perfect guitar sound that complements your music and style.

Conclusion

Miking a guitar amp is a craft that involves understanding the characteristics of microphones, the importance of placement and distance, and the intricacies of phase relationships. By choosing the right microphone for the job, experimenting with various placements, and blending different microphones when appropriate, you can unlock the full potential of your guitar amp’s sound. Embrace the journey of exploration and discovery, and let your creativity guide you toward achieving the most captivating and expressive guitar tones possible. Whether you’re in the studio or on stage, mastering the art of miking a guitar amp will undoubtedly elevate your guitar playing and recording experiences.

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Chadwick Becks

I have two degrees in guitar performance and was privileged to study under Aaron Shearer, Tom Kikta, David Skantar, Ken Karsh, Tim Bedner, and currently Christopher Berg. Outside my editorial work on this blog, I teach full-time across many genres including classical, jazz, blues, rock, funk, and metal.

A Comprehensive Guide on How to Mic a Guitar Amp for Stunning Sound