How to treat around a protruding ceiling beam?

[Cloud10]

Hey all. I have a really specific problem that has got me stressed out and I'm hoping that someone can help. I just recently built a room according to the plans listed in the following link with one problem, there is a steel I-beam in the ceiling, with a duct running parallel and just next to it, which protrudes below the height of the joists about 6-8".
http://realtraps.com/art_studio.htm
I've scaled that design down to 91" H x 239" L x 125" W short wall and 171" W long wall. The beam and duct run across the center of the ceiling, diving the room about in half from front to rear. I'm doing my best to follow that design as closely as possible but I need advice on how to treat that beam and duct. My plan for the ceiling is to stuff fiberglass batts between the joists, then hang rockwool sheets below that, and then cover that with burlap. I'd also like to follow the design plan of having the ceiling perimeter around the cloud covered with 1/8" plywood. Since I now have these extra two "corners" in the ceiling should I plan on bass trapping on either side of the duct/beam? Should I consider the whole length of it part of the "cloud" section and cover it with rockwool/burlap? Or would I be better off leaving the reflective perimeter intact, i.e. creating plywood soffits around the ends of the beam/duct? Someone just please tell me this isn't going to completely destroy the usability of the room!
I'm planning to use the room for recording and mixing rock, including some live bands. Isolation is not a major issue because the room is in the basement of my own house and I can get away with some noise. My primary concern is how to best retain the acoustical integrity within the space.

[Soundman2020]

Photos and a SketchUp model would help to understand the issue.


- Stuart -

[Ethan Winer]

there is a steel I-beam in the ceiling, with a duct running parallel and just next to it, which protrudes below the height of the joists about 6-8".

With room acoustics what matters most is the big stuff like overall room size and shape. From what you describe, the beam and duct can probably just be ignored from acoustic calculations. If the duct is the sheet metal type, then it's mostly invisible to low bass frequencies anyway. Even if it's sheet rock, unless the lower height affects a large percentage of the ceiling surface it won't matter for a mode calculation.

I hope that helps reduce your stress level.

--Ethan

[Cloud10]

Ethan, are your DIY membrane bass trap designs suitable for this room design? I'm thinking about one low bass trap, and one mid/high bass trap in each corner, floor to ceiling. Would you suggest another type instead for that layout? Thank you so much!

[Ethan Winer]

For a small room like that I'd use broadband traps. From the top of my wood panel bass traps page:

Please understand that the bass traps described in this article are intended mainly for larger rooms. For rooms smaller than 25 by 15 feet you'll usually do better with broadband bass traps made from thick rigid fiberglass placed in the room corners.

--Ethan