[WGH]

Between 2008 - 2012 I tracked down 11 white papers by Floyd E. Toole, Ph.D., Vice President of Acoustical Engineering at Harman International Industries and Todd Welti, Research Acoustician, plus the hard to find Room Mode Calculator from Harman International and put them all in one place - here on AC.

Loudspeakers, Rooms, and Subwoofers - Audiophile Articles
https://www.audiocircle.com/index.php?topic=58304.0

The Harman Room Mode Calculator is from the Harmon website when it was last available (it is the same as the calculator linked to by CherylJosie)
http://www.wghwoodworking.com/audio/RoomModeCalculator.zip

Play with the calculator after reading the articles by Floyd E. Toole. Part 2 of "Maximizing Loudspeaker Performance in Rooms" has detailed information on how to interpret the graphs.

The calculator uses Microsoft Excel or compatible spreadsheet for the calculations.
Toggle between WAVES and MODES at the bottom left of the spreadsheet.

[js1955]

@CherylJosie........wow, that's quite the dissertation!  Thanks so much for taking the time to provide all that info.  It will take me awhile to digest it.     

@studiotech......I agree with you about AF being way overpriced.  I've already priced the DIY absorptive panel possibilities, and watched many YT vids on how-to assemble.  One can build identical panels to what the pros sell, at a fraction of the cost.  I have plenty of time and the skill set needed, so DIY is my path.

To start, I figure I need at least twelve 2' x 4' x 2inch panels (4 each for the window, front and back walls).  Buying pro is beyond my budget.   I will adjust things regarding quantity and placement as I proceed.

Thanks again to all for the very helpful input.

PS:   of all the online vendors of 2 inch OC 705 bundles, Acoustimac has the best price per piece (including shipping).  It works out to $31 / piece, all in.   It's rigid enough so I plan to go frameless, as per the video I linked earlier.  Add a few bux for fabric covering, spray adhesive and mounting hardware and you're at about 40 bux per panel.   Compare that to the pro made stuff plus shipping.

DIY framed panels will be a bit cheaper, mainly because the internal material (Rockwool or similar, not OC 705) is cheaper, and no shipping charges as it can be sourced locally.  But obviously more labor intensive, and a heavier end product.

[js1955]

Back to  my original question.   I haven't seen any comments/advice/input on it.

Thanks in advance.

I know it's best to put a 2 inch or so air gap between panel and wall.   But for the panels over the glass, I'm not sure what to do.
So I have these questions:

(1)  Should I put panels flush on the glass?

(2)  Should I put some bumpers behind the panels to create an air gap between panel and glass?

(3)  Should I install some hardboard on the rear of the panel, and use bumpers between it and the acoustic material to create an air gap?

I'm not sure, but I think (1) and (2)  will result in sound waves going thru the panel and still bouncing off the glass?

Under scenario (3)  I figure:  (a) the hardboard effectively replaces sheetrock that is normally present, (b) the desired air gap is present,
and (c) the glass is taken out of play......so it is probably the best option?

Is my layman's logic and intuition correct?   Should I be doing something else?

[JLM]

My GIK 244 absorption panels have a 1.5 inch air gap behind them, hardboard (with small holes) goes on the front of the "bass traps".

[js1955]

I know it's best to put a 2 inch or so air gap between panel and wall.   But for the panels over the glass, I'm not sure what to do.
So I have these questions:

(1)  Should I put panels flush on the glass?

(2)  Should I put some bumpers behind the panels to create an air gap between panel and glass?

(3)  Should I install some hardboard on the rear of the panel, and use bumpers between it and the acoustic material to create an air gap?

I'm not sure, but I think (1) and (2)  will result in sound waves going thru the panel and still bouncing off the glass?

Under scenario (3)  I figure:  (a) the hardboard effectively replaces sheetrock that is normally present, (b) the desired air gap is present,
and (c) the glass is taken out of play......so it is probably the best option?

DUH, what was I thinking?!    Over-analyzing things. 

Doesn't matter if sound waves hit glass after going through absorptive panels.   They will re-enter panel and get absorbed again.

      squared!

[toocool4]

Both Rockwool / Roxul and Owens Corning are commonly used by many reputable panel mfrs  (ie:  GIK, ATS, Acoustimac), and all the specs I've seen online, including this one,  say the NRC (noise reduction coefficient) across the mids and highs is comparable on both products,  in the 1.0 range. 

The companies you named are using Rockwool / Cornings etc, I too like a lot of people do use GIK yes they work to a fashion and did make some difference to my room. What they are using as padding in their products are general building purpose material and do not do the job as well as solutions designed purposely dedicated for audio.

I will carry on using my GIK panels, but when I go to have my room done again, I will not be guessing at it I will have it done properly.