Redesign small control room

[soall]

Hey,
First post for me, I'm very happy to join the forum
I’m currently trying to improve my control room acoustic, every advice would be greatly appreciated !
Long story short : 4 month ago I downloaded REW, worst mistake of my life
Here are some pictures (sorry for the poor quality)

Front wall room .jpg

Rear Wall.jpg

Control Room size:
Length : 4.53m
Width : 2.43m
Height : 2.25m

The control room has already been treated by an acoustician:
Treatment already in place:
- Lower half of front wall -> 7.5cm rock wool cover with fabric
- Top half of front wall -> resonator
- Ceiling -> 7.5cm rock wool cover with fabric
- Rear wall -> 3 resonators
- Side walls -> nothing except fleece and fabric (I added GIK acoustic basstraps at first reflection points)

Here are the REW files (every treatments in place except GIK panels) : https://www.dropbox.com/s/z9cgqgfn3fot1 ... .mdat?dl=0
Distance front wall / listening position : 1.72m (38%)
Distance between monitors : 1.6m
End of equilateral triangle 30cm behind my head at 2.02m from frontwall

Objectives list would be:
Reduce 80hz - 150hz null
Get all first reflections under -20Dbfs
Reduce decay time below 132hz

Problems identified:
- No side walls treatment
- Ceiling treatment too thin
- Front wall resonator not effective
- Front wall porous treatment too thin
- The 2 big rear wall resonators shows up in ETC

After investigation:
It looks like most of my problems come from SBIR and side walls reflections:
.Keeping the listening position and putting the speaker in the corner (front wall/right wall) did reduce a lot of the null.
.Putting Gik acoustic soffit basstraps all around the speaker did reduce a lot of the null.
.Treating whole sidewalls with soffit basstraps did also reduce the null but I can't live with 40cm basstraps on each side and 15cm panels weren't deep enough.

I removed the porous treatments from the ceiling and the lower half of the front wall.
I don't think that 7.5cm rock wool will do anything to sbir or mods ...
I'm also gonna remove the resonator from the top of the front wall, construction is not sealed correctly and design is weird:
2.5cm thick slat, 9cm air, 7.5cm rock wool, too much air and not in the right place no ?
I'm happy with the 2 big resonators at the rear wall (60cm deep, 40cm of rock wool inside) (still they do screw ETC shape a bit)
Front of the room right now:

CR Room 27 march.jpg

About the walls:
The floor is a parquet which I ignore construction details (not treated for sure).
Front and rear walls are made of layers of breeze blocks + plasterboards (hard but not that much).
Ceiling is hard.
Left wall is made of 6 cm plasterboards.
The right wall is supposed to be soundproof it has a window and a door who leads to a small rec room.
The design looks like : 2 * 1.6 cm OSB glued - 9 cm Air - 1.6 cm OSB. Sadly it has been poorly made :

Right Wall.jpg

I'm not an expert but I don't think this is the right way seal a wall

Right wall problem.jpg

Anyway isn't the sound going to pass through the parquet even if this was nicely done ?

Possible solutions ?:
I don't mind that the wall which leads to rec room is not really soundproof as I don't use it anyway.
So if it's possible I would prefer not to bother about it.

Without thinking about construction details what I have in mind is:
- Transform the entire front wall in a huge damped broadband resonator, something like this:

Front wall basstrap.png

-Treat the 30cm of the ceiling just above/behind the speaker with damped broadband resonator, something like this :

Ceiling resonator.png

-Treat the ceiling above listening position with 15cm of porous absorber

-Treat side walls with same type of broadband resonator except at first reflections points where I'll put 15cm of porous absorber

I'm gonna update my post with a sketchup file of what I plan to do, but I still have to work on it (First time on sketchup)

Any contributions will help

[DanDan]

Someone asked a question..... will a resonant absorber fix SBIR. I have been pondering that ever since.....

Your room is small, similar to mine. But at least some of your boundaries are a bit floppy at LF. Mine is all concrete except the ceiling.
I have big SuperChunks in three corners, but my primary 35Hz length mode is still about 700mS. So I use Dirac Live to tame that.

There is a lot of focus on Modes, but then we all find ourselves in your situation, with this damned LF hole. Covering the fundamental notes of the music!
https://realtraps.com/art_modes.htm

The BIRs from your Front Wall, Side Walls, Floor, Ceiling, will all gang up. Some stronger than others due to a massive boundary, distance, treatment.

You might, might, be able to identify a dominant gang member, perhaps the front wall. Try moving a speaker around while measuring the response, or faster, watching it on a Spectrum using Pink Noise stimulus. Try moving the speaker towards or away from specific boundaries. If the frequency drops when you move away from the Front Wall, you have a suspect Inspector Clouseau.

The Back Wall can join this BIR gang too..... But again moving the speaker towards suspects may deliver certainty here.

My gut reaction here is to suggest 60cm absorbent on the whole Front Wall. Before finishing it try sinking the speakers in, as far as touching the hard boundary. Sunk in like that may minimise BIR from all sources.

[gullfo]

not sure why you feel REW is a mistake - REW is your friend. just don't try to move in and share the bedroom...

in general - if you need isolation you need it in 3D - walls, ceiling, floor. this means mass and sealed. internally - you could make this booth using inside out techniques to leverage the interior frame for insulation and cloth to deaden it. then use slats and panels to bring life back.

given the height and width are nearly square you'll need some membrane or resonator traps on both sides and ceiling to be effective. some smaller units tuned to the low fundamental problem modes should go a long ways to solving it. you can't solve nulls... except by trapping the frequencies which are causing them, in the spots which are causing them.