Stuff to ponder if you get bored again.

As for projects, I've had some extremely interesting things on my plate. I'm itching to report some news about the cooling system I'm doing, because it's exciting. But what I have now is not quantified, just seat of the pants stuff so far.

Earlier this week, we connected the valve to a pump and the flow differential through the two sides was remarkable. I can tell the thing will work great, at least for setting up unidirectional flow. But the prototype was made with 1.5" ID, and it really should have been 1.25", so we had to machine an adapter. That isn't ideal, and will affect the testing. But the device worked so well on the bench that I'm confident even with a slight mismatch, it will still tell us what we want to know. It's ready for me to take and test, but I'm too busy to get it right now, so I'll get it tomorrow. I'll post some pics soon, to show you what I'm talking about. And I hope to have some demonstratable numbers very soon too.

I'm working on a new tweeter horn too. It's actually a re-hash of the one I designed for Martinelli to make. It was originally intended to have curved walls for top and bottom and straight walls on the sides, radiused to transition from the throat and at the mouth. But instead, Bill made the sides curved and the top and bottom straight. So I'm working on the updated version right now, and getting CNC stuff together. That's pretty cool, and I'm excited about it.

Speaking of Martinelli and the taller Theater three π you mentioned, that's exactly what his Arezzo was. It was a taller, thinner Theater three π loudspeaker. If you like it that way, just shift the woofer up in the baffle and mount the tweeter externally. Even leaving the cabinet dimensions as they are, just moving the tweeter outboard makes it taller. Or you can modify the cabinet a little to make it even taller and thinner like Martinelli did to create the Arezzo. Each of these configurations of the Theater three π loudspeaker are good, it's a great little loudspeaker in any flavor.

The idea is to remove heat from the speaker using a ducting arrangement and an intercooler. Speakers in very small boxes may not vent hot air effectively because the pressure in the box impedes are movement. The air inside the box may become more and more heated too. So by venting into an intercooler, I am hoping to remove the heat more effectively. This will increase power handling and reduce compression. It will also reduce the shift of electro-mechanical parameters towards an underdamped alignment as the voice coil becomes hot.

Certainly, the main focus is on high-output woofers in prosound, but it may also prove useful for high-output home theater subwoofers too. It's a pretty simple system with a valve, a couple of hoses and an intercooler. All of it except the flow valve is available off-the-shelf, and the valve is easy enough to make. If it proves to be successful, I'll make the valves avalable at low cost. You can insert them into the cooling vent of most woofers, so this option is open to just about everyone.

• Loudspeaker Venting and Cooling Techniques