Isolation-spring reverb box with active preamp for acoustic instruments

I’ve written before about spring reverb and contact microphones, but here is a special project where I applied them both. I’ve always liked the simplicity of cigar box instruments, so that is likely the inspiration for making a spring reverb tank using wooden housing. I’ve taken the wooden dowel plugs from my acoustic guitar spring reverb kit to stretch the spring from both ends within the box. Luckily the box was the perfect size for the spring, I only had to shorten the plugs slightly to make the spring stretch across the box far enough to get a good sound. As pictured below, the contact mic I used is fixed under a thick foil layer that acts as a shield for interference.

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Using the Alex Rice phantom-powered preamplifier design was important to amplify the subtle vibrations created by the spring while the box resonates. My idea was to implement an auxiliary microphone for larger acoustic instruments such as the piano, or complex percussion with the spring reverb tank creating a distant or hallowed effect. Being that the spring is a metal object and produces an inharmonic spectrum, the span of sound it resonates with is wide, but the tank does have a tendency to emphasize the lower frequencies. The fact that the box itself is wood will allow it to vibrate nicely alongside acoustic instruments; placed atop or beside should do the trick to capture the sound and produce a very evocative treatment of its original source.

If you are interested in having a spring reverb tank made for you, I’d love to be in touch. You can use this contact form for all inquiries.

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