choice of midrange cap?

You could use two Sonic Caps to make up 40uf.

Clarity makes a 39uf. Ive used with comps and fostex t500a, on the t500a I use mundorf silver gold.

There are no problems with combining caps. I agree with John, try clarity caps.

Johnk: I see that Clarity has three versions. Any noticeable difference between them in your applications?

Guys: How do the voltage ratings come into play? I like the thought of using a lower voltage value to take advantage of the thinner di-electric. Also, in the case of the high end caps, the cost savings are very substantial. FYI, the amp would be less than 35W.

Thanks

Clarity SA is best value for performance given.

In my experience, nothing competes with the Duelund, but major money here!

The Mundorf Silver/Oil could impart a bit extra brightness.

Haven't heard the Clarity, heard good things about them, however.

Another cap to consider is the Jantzen Z-Superior copper cap, really nice cap very few know about. Alas, only goes up to 22uf, would have to use two.

Also, what sonic complications are caused by say mixing a 25uf with a 15uf to make up 40uf since many manufacturers don't make 40's in certain compositions?

None whatsoever, especially in a generic/general sense. Of course, I'm sure that out of the hundreds of thousands of capacitor types available, you could find some combinations that are problematic . . . but there's no way to predict this without knowing all of the very specific, and generally unknown/unpublished, electrical characteristics of each. But with high-quality film caps, you're on very safe ground.

Now on the other hand, changes to the crossover design itself have a huge impact, and if this is a custom speaker system, then that's a better tree to be barking up . . .

Kirkus: That's good to hear as I was concerned that time smear would result from "by-passing" a 25uf cap with a 15uf to achieve 40uf. Thanks