Yeti mic doesn't sound good when working with Apogee mic

I have an Apogee mic and have just been given a Blue Yeti mic as a gift. I want to be able to use both of them simultaneously to conduct interviews into my Garage Band on my Mac Book Pro.

I was finally able to get both of them working together, by creating an Aggregate Device, etc, (and a lot of tweaking), but now the Yeti sounds very hollow, like I'm recording in a bathroom. The Apogee wasn't affected. I disconnected the Apogee, opened a new GB window, and tried just the Yeti, and it was back to sounding really good. Any ideas?

Thanks!