"Travis Jordan" wrote:
You can't get there from here.
The duct diameter is: 3.00 inches
Flow Rate 75 CFM
Velocity 1530 FPM

Let's see, the duct cross-sectional area is just about 7 in^2. One
cubic foot of 3" duct would be 12^3 in^3 / 7 in^2 = 247" = 20'. Hm.
So the whole 20' length only holds 1 cubic foot!? I hadn't worked
through that before...

At 1530 FPM, any fan is going to make a lot of noise.

I'm not concerned about the fan noise. It's 2 walls away. I assume
you meant turbulence noise in the duct? I can tolerate some of that,
just not as much as the shopvac made. The duct is inside the plenum on
top of the projector, and the plenum is made up of 2" thick foam
running around the edges of the projector & jammed between the
projector and the ceiling. That will contain a lot of the noise.

How about opening up the ceiling over the projector and just
venting it into the attic?

No can do. The projector is in the basement. The ceiling over the
projector is the floor of my wife's office. She would not appreciate
the hole in her floor. :-)

"Matt" wrote:
How about getting some silent PC fans, mounting them on the sides of
the projector box, and forgetting the duct entirely?

With a 7.5A draw, this thing is pumping out something close to a
kilowatt of heat. I need to exhaust the heat from the room or the room
gets uncomfortably hot and the projector overheats. It's worse if I
have 6-8 people in there watching a movie.

Gary