5.1 Mixing environment, would appreciate comments

[newmancl]

I work for a film department in a university. I have been tasked with updating our 5.1 mixing lab. It is currently just a rectangular room with 5.1 speakers and a pro tools 8 hd system. I plan to float the floor, hang the ceiling, and build interior walls that are nonparallel. I am principally a sfx editor and my knowledge of room design and physics are rudimentary. I would very much appreciate any comments.
I will attach a google sketchup of a cutaway of the room.

Thank you so much

[Ethan Winer]

Much of what you describe sounds expensive and is probably not needed unless sound isolation is a requirement. Assuming the university has a budget for this project, you might consider hiring a professional acoustician. Or at least buy treatment from a knowledgeable vendor who can guide you.

--Ethan

________________
The Acoustic Treatment Experts

[jaddie]

So far, you are focusing on isolation, with a smattering of room acoustics. Before you spend a ton on isolation, you should determine the noise level in the existing room, and what the noise sources are. If there are noises from outside the room that cannot be controlled, then you need isolation. If the room is already quiet, and the sound you make inside that leaks out won't bother anyone, you don't really need it. That said, constructing a high STC wall is NOT a simple process, and a small error in construction can take a 70dB wall and make it a 40dB wall. Not for the novice, to be sure. Also, much room noise comes from HVAC, which isolation won't address of itself. You are looking for low entrance velocities, with some form of sound transmission loss in the supply and return ducts (duct silencers, etc.)

Interior acoustics is also tricky, and specialists still have trouble with it. Splayed walls may help you, but they also make predicting reflections much harder to do. Rectangular rooms can work well too.

For 5.1 rooms, ideally, the mixing room should match the exhibition space as closely as possible. So you have to ask, how will most of the 5.1 material you create be used? Small or large room, theater or home, etc. A good 5.1 room, though, can translate well to most end uses.

No time at the moment to write the details, perhaps later. But I recommend two books: Surrond Sound: Up and Running (second edition) by Tomlinson Holman, and Tom's other book "Sound for Film and Television". The latter is less about surround in specific, but still required reading.

More later, if I get time.... or you could just hire me !

Jim

[andrebrito]

I don't know... splayed walls in a mixing room for 5.1 .. me not like that solution at all ! Splayed walls makes sense in stereo rooms but in surround rooms I would stick with a rectangular room.. but that's me..

Hire someone to do this

Andre

[avare]

Originally Posted by andrebrito

Hire someone to do this

+1.

Andre

[jaddie]

It's not just about splayed walls, it's a complex relationship between the size and shape of the room, the permeability of the walls, absorption, diffusion, and all the things in the room. It's not simple. However...

If this is a non-budget, DIY sort of project, I would suggest doing your homework on acoustic design (means: read up), and give it your best shot. Then, when it's all done, drive your monitor system through an Audyssey Sound Equalizer, or a high end HT receiver with Audyssey XT Pro. Call in a certified Audyssey calibrator to set things up, and you'll be set as good as you can be without paying a consultant.

See...some of us consultants are willing to give something away! Of course, if you want the best results for the investment you make, you'll still want a professional involved, particularly when it comes to isolation issues, which Audyssey won't address. No calibration system can substitute for experience and knowledge. I would suggest that to whoever is supplying the budget, our you might be personally held responsible for the results.

Jim

[avare]

To give some idea of the established parameters for 5.1 rooms, read:

NARAS P&E Wing Recommendations for Surround Sound Reproduction and
AES TD 1001Multichannel Surround Sound Systems and Operations .

The latter has hot links to further documents.

Andre

[newmancl]

Fortunately our university is associated with a movie studio so budget and consultants will not be a big issue once i get a preliminary proposal approved. I really appreciate the advice, both pos and neg, about splayed walls. The isolation is more for people outside of the room than it is for the mixers in the room. the environment is already quite quiet. If anyone has recommendations for quiet ductwork i would very much appreciate it.

Thanks again for the advice you all gave me, especially the books.

Sincerely, cliff

[avare]

Originally Posted by newmancl

Thanks again for the advice you all gave me, especially the books.

I suggest that you start with the P&E Wing document.

Andre