I think that if the Vtc,and Vrc are similar and not too different the loading will be equal. (infact perhaps the loading wont change just the individual horn parameters)

-off to town to hear 1" HF horn + 15" and quiet bass!

Regards
Mike.e

Cheers!

I'm thinking of doing something like shown above. I'll have the vent hole on the speakers fitted with a pipe fitting. It can be threaded, but I think a press fit is sufficient for no more pressure than we're talking about here. I'll also mount an exit fitting on the back of the cabinet and run a large rubber hose between them. Something like a heater hose, using the same diameter as the speaker vent. I'm thinking that this approach should really help keep the voice coils cool, and prevent unwanted noise at the same time. It's not a very difficult thing to do either, just a couple of fittings and a hose between them.

The other thing I'm thinking of is how to mount the drivers. They can have access panels or the entire motor assembly can be removable, and fasted with a series of studs, somthing like mounting the head of a car to the block. I'd probably make the horn complete all the way to the throat and then have a matching cutout in the plenum. The drivers can be accessed through that cutout. That would allow the entire assembly to be made solid and without access panels, which would probably make for a better seal. The two surfaces that meet would employ a rubber gasket, and they would be pulled together tightly using a series of fasteners like head bolts.

Regarding heat removal could you offer options depending on what the persons most common use for the speaker is? One thing I realize is that you don't have a "typical" user for some of your designs and what is "best" for one person isn't for the next. Adding some noise might be a tradeoff worth making if it provides much better cooling for some people. Having test numbers to compare options would help people make their choices.

I like the idea of quick access panels over removable assemblies. Removable assemblies open up opportunities for vibration, poor fit if building isn't percise, and loosening up over time.

Enjoy your Sunday.

Grant.

nice idea/simple to build & plenty of path - for home use driver requirements could be laxed - got any sims for 12" version w. couple diff TS?

Best,
Freddy

At power levels where vent turbulence becomes audible, the horn's output may be so much louder that the cooling vent is like a whisper in a tornado. But I think external ducts will probably enhance cooling, which is a good thing at higher power levels. They wouldn't be very hard to add either. Failures in LABhorns have been mostly thermal, so this may help solve that in addition to reducing distortion.

It will be interesting to see if there is much of a difference with this system once you test it.

Best wishes.

Grant.

But the problem is that when a driver is mounted in a very small box, it starts to contain the heat. If the box is very small, it acts like the vent weren't there at all. So horns with small rear chambers are likely to suffer from heat related problems.

In a horn with a small rear chamber, there is less heat exchange because the back chamber air gets hot and can't dissipate. I imagine it gets pretty hot in there at full power, and then the vent doesn't provide much cooling. Some have used metal chamber panels in an effort to conduct heat to the surrounding air, but it seems to me that a better solution might be to just vent to outside air in the first place.

I guess the real test is to plumb the system for outside venting and see what happens to power handling. Then we'll know how much benefit it brings.