Request for assistance please room treatment

I see mentions of the RS SPL meter. I suggest getting the Studio Six apps for your I/O device. It is waaaay more flexible and accurate. It does so much more than just SPL. I even grab it for professional use, even though we own really expensive B&k instruments. It is just so convenient and well thought out. I am going to be carrying one tomorrow at a show I am working at.

Also, while looking at frequency info is certainly useful, combining that with the time domain gives you a much better picture of what is going on in a room. You really need to look at both to analyze a room. Pretty cheap to do these days with Studio Six!
Rich

I have gone so far as to reading Master Handbook of Acoustics, watching lectures and doing room measurements. For the novice, like you and me, it takes trial and error. The initial big deal seems like speaker positioning, then addition of acoustic treatments. Its important to keep in mind that acoustics behavior changes a lot depending on frequency. Simplified, treating high frequencies, which behave more like rays reflecting off boundaries is easier and very different from low frequencies which are subject to room modes, while "middle" frequencies act like waves. Acoustic management also has to be split up in both frequency and time domains, which are interrelated.

I'm with Richz (of course he is an expert and I am not) and also somewhat disagree about the SPL meter alone. Acoustic software like Room EQ wizard with microphone, and usb audio interface yields more precise, more accurate and more user-friendly results along with reverberation time information. IMO well worth the relatively modest extra cost.

You can look at bobgolds (online) room acoustic calculator to get some idea what you are dealing with but its not going to be perfectly accurate.

First thing I recommend is with only the things that have to be in the room play and finalize speaker position. You cannot position speakers in a room with room treatment. You will find that when you get the best overall sound the room will have the least negative effect on the sound. Then one by one you can bring in acoustical treatment to fine tune the sound.

You want to be very careful what materials you use to control the rooms reflections so it does not not over damp the room and worse cause comb filtering effects ( large peaks and valleys in the frequency response). Most absorptive material will absorb at certain frequencys and reflect at others. I use very light material to only delay reflections and not to absorb them.
Defuser's are also a good thing to use, so as not to absorb sound but to eliminate slap echoes.

I believe in keeping the front wall reflective, NO absorption, defuser's are ok, with very slight absorption on the back wall. Side wall reflections are again best addresses with defuser's.

I suggest installing one at a time so you can hear what each one is doing and where it is taking you acoustically, until you get the desired results you prefer.

It takes time and patience
As far as bass modes, those are very difficult to address. Your room dimensions show bad ratios and will have many bass mode issues. At 50hz, 75 hz, 101hz, and 150hz. Bass draps do little to nothing. Only two options is alter the room dimensions ( build a room with in the room) or helmholtz resonators. These must be built and tuned specifically to the rooms modes.speaker placement will definitely effect this too, so make sure you do that first to try and minimize those room modes. Any other questions feel free to ask. A good size area rug or simply carpet on the floor is also recommended to treat floor to ceiling reflections.

There has been a lot of good suggestions. Every room is going to have issues. Are your speakers set up using the 1/3 or 1/5 model? For example are the speakers about a 1/3 into the room and your listening position about a 1/3 from the back wall? The corner traps are probably OK but I would remove the absorption panels from the front wall. We can't see the sidewalls but at the first reflection points diffusers may work better than absorption. The back wall would benefit from some diffusers but we can't see any pictures. Also as mentioned some toe in of the speakers may help perhaps with a focus a couple of feet behind your listening position to start. It's a trial an error process. Get the bass right by moving the speakers around and then focus on the soundstage and image by the distance between the speakers and toe in.

Forgot to mention if you have ceiling panels you may want to try taking then down since you have carpet and an area rug. The room may be getting to dead. Just a thought