I tried Tom Danley's cooling idea from the patent at
http://www.freepatentsonline.com/4757547.pdf. I have some questions. I got cooling plugs and they work great. Now I want to try Danley's idea too. The cooling plug is threaded at one end so it makes it easy to add a pipe fitting for fan air.
I did a experiment and hooked up a fan to give a blast of air. I took Wayne Parham's sugestion to use the cooling plug as a fitting for the fan. The fan is in a funnel with caulk all around so it makes a blast of air out the small end. I hooked that to a tube and used a pipe fiting on my cooling plug.
The air rushing out of the magnet hole blasts with woofer movement even if the fan isn't connected. The air blasts are enough to move my pants leg! It turns the fan just from woofer air blasts!
The fan moves the woofer cone forward. How bad is that? Parham said it makes the speaker suspension stiffer in one direction and looser in the other. How much is too much? I know it makes more distortion and less xmax by shifting offset, but Danley must have figured something out. What can I do about the offset besides taking off the fan?
Does it only work with a specially designed woofer that has a cone that can move further out than in to make up the difference? Maybe a special speaker is a requirement for this to work? If there are exit holes maybe that will help. I think the problem is the restriction at the voice coil gap so the fan air will still push on the back cap a lot but not on front of the cone. That is my dilemma.
Here is what I tried. If I don't use much fan power, the woofer moving air blasts spin the fan by itself, so it isn't much use. If I use more fan power, the fan spins normally but the cone moves out further, sometimes almost as far as it can go. I can change fan speed in between, and that works sort of. The Danley patent uses power from the signal so it won't make the fan go unless power is high. I think the woofer will be pushed forward a lot by the fan when power is high though. That seems like it would still be a problem. Even if power is high, I don't think the cone should be shoved forward. Thoughts anyone?