I saw this over at Hack-a-Day and while this is nothing new, its still worth blogging about. This is a great example of how hacking every day things to create new useful things is cool. Expecially if you make something that cost $300 for $20.
“Speakers and microphones are physically similar – usually mics are much smaller to allow decent high frequency response. In this case, [Nathan] wanted something to pick up kick drums or bass guitars, without the cost of a commercial version like the subkick. It’s build around a dual coil 12-inch subwoofer. The passive circuit design allows the coils in the speaker to be configured for differing impedance, phase and isolation.” Link