Massive flutter problem

[Holm]

Hello there!

It is a great site and has loads of information, unfortunately my problem is that I am not experienced enough in Acoustics so I can't actually make wise decisions yet as of what would be the best possible solution to my particular problem.

The recording room of my studio is on the drawing I attached here. I sorta inherited the room with all it's flaws. The size of the room is 3 metres high (10 feet), 6 metres wide (20 feet) and 9 metres long (30 feet). Not the best possible solution, but actually the´from concrete to conrete walls the length' of the room is rougly 15 metres on one side and 12 metres on another, roughly half and half of each. Control room is to the left of the recording room in the drawing.

Second problem. Most of the outer wall is glass window and I will NOT cover this in any circumstanges permanently, clients just like it too much.

The acoustic treatment is glued on all the walls except the one that has windows on, and is 18mm thick and seems to be a cross of fiberglass and sheetrock, it is porous, but rigid, still it doesn't hold screws in. And it reflects very well the high frequencies - this is apparent from the slapback echoes I get from the 30 feet long wall in my room.

These were all relatively minor problems, I get MASSIVE flutter roughly at and around the spot marked with X in the drawing. It is so bad that when you speak at that spot you don't hear much of your own voice at all, you hear mostly bounces from the walls at roughly 800-1000 Hz. It rings quite awfully.

So far I have solved the problem by building massive removable walss, with one reflective, diffusing side and another dead side. Now i want to do something permanent.

Another problem, I have a shortish reverb everywhere in the room somewhere around 300-500 Hz.

So I would like a solution that hopefully would get rid of BOTH of these problems, the flutter echo around 800-1000 Hz and short reverb around 400. Also, the thing should be reflective on high frequencies aswell as I hate dead sounding rooms. So some diffusion would also be great.

With my limited experience so far the Helmholz resonator solution John Sayers described in
http://johnlsayers.com/phpBB2/viewtopic.php?t=323 seems to be the most promising, but this is all on paper. I would put this type of boxes in a sawtooth pattern (an angled box about 4 feet width, then 2 feet gap, then again 4 feet wide box etcetc, this was suggested to me by a local acoustics engineer) on the wall opposite to the windows.

Maybe there are simpler solutions to my problems or maybe this will not work at all?

Thanks all!

Arne Holm