Anyone with any experience?
I have an upstairs bedroom that I want to improve the AC flow. Do inline duct fans help? Is it better to put a fan on the return line or the vent into the room?
I have two relatively inexpensive 6" fans in my heating ducts. They are noisy in both the feed and return lines, with the sound telegraphing over and through the entire length of the steel duct. I have read about in-line blowers -- wheels rather than blades, I believe -- being much better, but they also cost quite a bit more. Also, I read somewhere that soft ducts do not telegraph as much.
If you do a web search for "duct fan" or "duct blower", you will find a lot of info and types available.
squirrel cage fans make less noise than blade fans. They also cost more.