Passive amplifiers have been doing their acoustic trick since before the Victrola was cutting edge. It’s pretty simple, really– just make some noise on the working end of a horn and you’re likely to hear it a little bit easier in the direction it’s pointed in. The concept works in reverse, too.

This eco-amp from the folks at Eco Made is a die cut piece of 100% post consumer chipboard that you can fold together into a fully functional passive amplifier. It comes unassembled flat, so it’s easy to store until you’re ready to use it. [via gizmag]