The "No suitable audio devices" message

Hi, I’m a first time Ardour user. I downloaded jack, but now I’m getting this message. It tells me that I have no audio device capable of simultaneous playback and recording installed on my mac. This just isn’t true, I use simultaneous recording and playback all the time on Garageband. My mac IS capable of this. What’s going on here?

For some stupid reason Apple changed the audio system couple of yeras ago.
You need to use Audio MIDI Setup to create an Aggregate device.

Here is a easy to follow description:

@AndyRafael: this strongly suggests that you did not read as was requested …