Need Advice Accurately Calculating A Reflection Free Zone

Hi all, I'm moving into a space next week, and devised a project to calculate the relationship in intensity between the direct sound and the earliest reflections, first with just the walls and windows in the room, and then with absorption. How can I accurately do this? I have a calculator and Fuzz Measure to use. I'm not sure how to take the "average absorption coefficients" into account when doing the calculations. Using the Everest and Howard/Angus books, I've calculated that the earliest reflection (sidewalls) will be 2.615 meters, coming out to 7.60196 ms of delay. The delay of the direct sound to my monitoring position (1.0668 M) is 3.101 ms. The difference in peak sound intensity and the earliest reflection is 8.34966 dB, which makes the difference between the direct sound (0.56166 dB less than peak) and the reflected sound 7.788 dB (with a 4.50079 ms delay difference). Both of these numbers fall under the recommended parameters (8-20 ms for the initial delay gap and 15 dB difference b/t direct and reflected). But, these numbers, while helpful, can't be totally right since I'm not taking the absorption coefficients into account. Any suggestions would be GREATLY appreciated!

are you doing this to calculate the amount of absorption you need for the room treatment?

basically, yes. i'm looking to lower the earliest reflections from the monitoring position. so i want to be able to put up various absorbers, and then compare/contrast the untreated room to the treated room, and then adjust accordingly. unfortunately, time is an issue, so i'm try to do as much calculating as possible before actually putting up absorbers and running tests. i found in an everest edition that the "noise reduction coefficient" is the average of the absorption coefficients for 250, 500, 1000, and 2000 Hz rounded to the nearest 0.05. would this be something to use to calculate the various surfaces, and then take percentages?

how is the rest of the room treated? while treating the first reflection points is important, the rest of the space can also impact the mix position.

right now the room is bare (drywall, door, and windows). i was planning on doing the RFZ first, and then potentially trap the corners (my fundamental axial modes are 48.43, 44.03, and 62.78 Hz) and diffusers. i have 18 oz heavy-set curtains for windows, and 703 1" and 2" for absorption. as for measurements, i have fuzz measure, an oktava omni, and a calculator! i haven't done any reverberation time calculations yet, cause i don't know how accurately take the average absorption coefficient of materials. i have to do the RFZ first as part of a project I agreed to do, so was hoping to take care of that first.

depending on how much of the treatments you're going to construct into the space versus just placing absorbers on the walls and ceiling, it might be easier to get into the space and make actual measurements and then treat with corner broad band trapping, as well as first reflection points and the back wall. then see what is left to do in terms of any significant deficiencies from those low modes which are closely related (almost a square room)... could be you'll need panel traps to fix those.