aggregate devices under OSX

[membrain]

I tried using the aggregate device function (OSX combines two or more audio devices so they are seen as one device) to get a main and a monitor output. It works! but with some limitations.
I'm using an imic and my laptops internal audio. It works well, the monitor output through the imic is a little delayed from the main output but the main problem is analysing tracks. The program slows right down and won't respond when it's finished analysing. If I then switch audio in preferences, it's fine.
Anyone have ideas about why? It's not CPU load, I've waited until all activity has stopped and the program still won't play. I realise an audio interface with multiple outputs would fix this but I want to work out why this doesn't.
My understanding of aggregate devices is that it's like audio hijack, done within the OS at the level of core audio.

[selector97]

i can confirm this behaviour of the programm. i aggregated internal output device with xone:3D. ( Khz&sample rate of both devices matched)

have heard no solution up to now.