Problem with iMovie and microphones for voice-overs

"I bought an Onkyo SE-U55 and a unidirectional mono microphone to do voice-overs in iMovie. I was unable to get the device to be recognized by iMovie despite the fact that the device was recognized by the Sound control panel. Onkyo Tech support informed me that they got the SE-U55 working in iMovie, but to no avail, I was unsuccessful.

I learned the following from Griffin Technology: Any device registering through the Sound control panel as an 'External Mic' input, will usually be recognized by iMovie. In contrast, a device registering in the Sound control panel as 'Sound In,' will not be recognized. These selections are apparently made automatically when you connect the device. The Onkyo SE-U55 registers in the Sound control panel as 'Sound in.'

I subsequently purchased a Telex M-560, which is a super-directional USB digital microphone. It registers as 'External Mic' input and works great for voice-overs in iMovie. The Griffin iMic has a control panel that allows the user to select either input. Griffin Tech Support said that this device also works fine with iMovie - although it requires purchase of a separate microphone."