Friday, January 8, 2010
A Little Loudspeaker Project
I really enjoy loudspeaker projects. In designing loudspeakers, you can never know it all. You need a mix of physics, electrical and mechanical engineering, and esoteric things like psycho-acoustics. You have to think about how our brain formulates an image of a sound, how it locates it and decides that its true or false. You also have to think about what in our hunter-gatherer past may have influenced how we hear and how the physics of a twig cracking in the forest may influence our perception of music reproduced by loudspeakers in a room. Mind twisting stuff.
Anyway, I don't allow myself to get too wrapped up in these ideas and build more speaker projects. After all, how many speakers do you need to build for yourself? Once you've got one or more good sounding speaker systems, aren't you kind of done? Or at least should be spending your time on other projects that lie neglected?
That's what I tell myself to stay away from speakers until someone comes to me and asks for help building speakers for themselves. In this case, that someone is Dan Schillinger from work and he has an interesting twist on the whole project. He came to me and asked if it would be possible to build some speakers into some wooden cigar boxes that he has.
He brought them in, we measured them up, and it worked out that we could build an nice little satellite with a 1" tweeter and a 4" woofer in his cigar boxes. The cigars are Remi "Acid" brand and the specific style is Kuba Kuba. The boxes are nicely made and finished, although we did need to reinforce the box on the inside. I can say one thing, they definitely retain the smell of the cigars that were stored inside and these are the best smelling speaker boxes I've ever worked on.
Of course, a 4" woofer isn't going to go very deep into bass or play very loud at low frequency, so we needed a subwoofer. I found a good deal on the Tymphany LAT 250. This is a very unusual speaker that has 6 "speaker cones" driven by two motors, one on either end and connected by metal rods. The "cones" squeeze the air between them and the sound comes out the slots in the face. For just $25, we had to give it a try.
Naturally, Dan came up with an unusual and neat enclosure. In this case, it is an old ammo box that we reinforced on the inside. Note the hand shaved boards and the fantastic old patina on the wood, hinges, and clasps.
Overall, the project is coming together very nicely. The attached graph shows the frequency response of one of the satellites. A fair bit of time goes into designing a crossover that takes into account the frequency response and impedance of the speakers, but the result is very satisfying.
Of course, the project doesn't answer any of those big, theoretical questions. Its a fairly straight forward design using inexpensive components and unusual enclosures. But overall it will be a nice little system and I hope Dan will enjoy it for years.