How to Make a DIY Sub Kick Microphone Using an Old Guitar Amp

Creating a sub kick microphone from an old 6” or 8” guitar amp is a fantastic way to capture deep, rich low-end frequencies for kick drums, adding a powerful thump to your recordings. Here’s a step-by-step guide on wiring the amp and understanding the engineering behind this DIY solution.

Step 1: Setting Up the Wiring

To convert your guitar amp speaker into a sub kick mic, you’ll need an XLR cable and a few basic tools:

1. Identify the Positive and Negative Terminals: On your speaker, the positive terminal (usually red) will carry the signal, and the negative terminal (usually black) will serve as the ground.

2. Connect to XLR Pins:

   • Wire the positive terminal to Pin 2 of the XLR cable.

   • Ground the negative terminal to Pin 1 of the XLR cable.

   • Leave Pin 3 unconnected.

By wiring in this way, you’re essentially turning the speaker into a dynamic microphone capsule, capturing the low-end frequencies directly from the kick drum.

Step 2: Understanding the Engineering

In a sub kick mic setup, the speaker acts as a transducer, meaning it converts sound waves into electrical signals. When the kick drum produces sound, its low frequencies vibrate the speaker cone. This vibration travels through the wiring and enters your preamp as a signal, where it’s amplified.

Because sub kicks generate a high output level, you’ll want to use a preamp with at least a 10 dB pad to prevent signal clipping. This pad will help manage the intense low-frequency response, giving you a more controlled sound.

Step 3: Keeping the Speaker in the Amp Box for Frequency Control

By leaving the speaker inside the original amp box, you create a more controlled acoustic environment for the speaker cone. The box helps contain and maintain the low frequencies, preventing unwanted resonances from affecting the sound and ensuring a fuller, more resonant bass response.

Step 4: Placing the Sub Kick Mic with the Kick-In Mic

For a balanced and punchy sound, combine the sub kick mic with a traditional kick-in mic. Place the EV RE20 (or another kick-in mic) inside the kick drum, positioned near the batter head to capture the attack and midrange punch. Then, position your DIY sub kick mic about 4-6 inches outside the kick drum’s resonant head to pick up the deep low-end frequencies.

This mic combination allows you to blend both attack and body in the mix: the kick-in mic provides clarity, while the sub kick mic fills out the low end. Adjust the distance slightly if needed to find the perfect balance of thump and definition.