Wall treatments “Asymmetrical”?

I’ll start searching and watching Yt videos on how to use a meter like that. Sounds like a fun project. 
thank you Newbee

BTW, FWIW, I just checked EBay and these items are available if you want them. I'm somewhat relieved, I was thinking of loaning you mine. :-)

@newbee thank you for your guidance and thought of loaning me your slm. I’ll find one on eBay. 

@newbee I found both an analog a digital slm on eBay. Is there a guide that can help me understand how to use this tool in dialing in my systems?

I’m not aware of one. It is somewhat simple though. The Stereophile test disc has a set of test tones at various frequencies. You measure these test tones at the listening position using the meter. You can start out with your system set up in a typical triangular configuration and see what your overall frequency response is then move your speakers about (or as likely your listening position!) to smooth out nulls and nodes. There is a learning curve here so don’t expect to get an instant result. It takes a lot of time and patience. Be sure to take notes - I used a graph showing test point frequencies in a form where I got a visual idea of the frequency response. BTW, although you can measure the FR at various locations in your room, for the most part the results are not useful. It is the listening position that counts. I suggest you do some basic research on the internet on using a SLM meter for audio setup - you might hit the jackpot. I don’t know that I would rely on U-tube. But once you have digested all that Toole has to say and figured out how to get started in your room using the SLM and test disc is an excellent way to fine tune your system. You are right, it IS a project! :-) Ask questions, I’ll answer if I can.

BTW there is a tutorial (so to speak) on U-Tube by Audioholic's. I didn't listen to it but you might look at it and see if will help you. I suspect there might be much more.  My Goodle search was for 'speaker setup using a sound level meter'.