JBL 2446 crossing to JBL 2405 what frequency?

[David Ketley]

In general when you use a throat adapter going from a larger driver exit to a smaller horn throat entrance
you will loss some high frequency output. The constriction of the throat causes high frequency cancellations from the reflections inside throat, to a degree that happens even in non reduced driver throats.

Thanks for the information Mike I will just have to try with my 2405 crossed at 8000 hz with a 18db high pass and see how it sounds. With Heil tweeters before it sounded fine but they were the P5s.

I am just waiting for my boxes to be built for my 2245s I just don't have the equipment to make a good job of them myself.

[Mike Caldwell]

The reflections / standing waves happen in all driver throats, the small the driver throat the better the high frequency response due to the cancellations being moved to a higher frequency bandwidth. Some driver designs have almost no throat with the driver exit right at the end of the phase plug. On the other hand some horn designs take in account the throat length of the driver or lack for the horn to work as designed.
There's a always a trade off to be made!!!