August 2, 2023: Another brainfart

I think that most speaker builders start thinking about their next projects well before the current one is finished. Sometimes that feels like an attention-deficit problem, but the truth is that it is just a healthy part of the creative process.

While plodding along with the ADAU1466 code for the Marthas, it struck me that those 8-channel SSM3582/ADAU1466 boards could make a very nice desktop amplifier for an active speaker. And since the new code includes support for multi-way dipoles, why not try a desktop dipole? I’m still working on finishing up the Marthas, but I’ve been spending a lot of time thinking about these desktop dipoles.

The 8-channel amp boards are only $115, and that buys you 8 channels of high- quality amplification, plus the ADAU1452 DSP plus SPDIF input, Bluetooth, and decent quality analog input (using the PCM1808 chip). That’s a great start for relatively small investment. The amps on the board aren’t powerful enough for filling a room with sound, especially for a dipole, but they are potent enough for near field listening while sitting at a desk. I’m confident that there is plenty of power for the tweeter, upper midrange and mid-woofer drivers. Fortunately, there are pads on the board that make the I2S signals available for each channel, so it won’t be too hard to add a higher-powered amp for the woofer/subwoofer. I hacked a cheap SPDIF-to-analog board for the subwoofer channel for the Marthas, and the same trick could be used for the woofer channel of these desktop dipoles.

Another reason I’ve been mulling over this new project is that I’ve got some very nice white oak from a tree that we had to take down because it was sending roots into our septic system. So, the project name will probably be the “Antiseptics” or some other reference to that tree. I cut up some nice 22″ log sections for firewood, and I think it will be possible to use some of those pieces to make the baffle.

The baffle will be modeled on the top section of the Linkwitz LX521. The log sections are about 11″ in diameter, and I’d like to make the baffle and stand out of just one piece of wood. My band saw isn’t big enough to slice down the log, so I would need to rough-cut the baffle/stand using a chain saw. And I don’t have access to a large jointer, so I would need to make a router sled to get a reasonably flat face for the baffle. But if I could make those tools work, I think the result would be stunning. I’m probably going to start on these soon, because it is going to take a while for this wood to dry after those rough cuts.






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