Multiple Speakers

My computer is a new 13" MacBook Pro. My router is an Actiontek PK5000. I use 3 Airport Expresses to connect 3 sets of powered speakers to my network. I use my iPad for interface with iTunes for my music collection and for internet radio. All speaker sets work fine independently. When I select more than one set at a time, the speakers sometimes work fine, but at others cut in and out, sometimes separately, sometimes in unison. Anyone have a clue what the problem might be?

Probably one of the devices has throttled back the data rate due to local conditions.

You could try using AirPort Utility to see which is declaring a slow down.