About to invest in room treatments; GIK, RealTraps, DIY -- what is your experience?

+1 on ASC tunable traps. Movable, tunable available in multiple colors and if you want to resell, you’ll do fine. I have 4 and also had room analyzed and treated with Artnovion panels - absorption and diffusion. They are absolutely beautiful, if that’s a consideration for you. Definitely treat ceiling to eliminate slap echo. Good luck

@hide45: 

Regarding first reflection/first order/side wall reflection treatment:  Don't use anything less than 6".  Some of the best engineers will recommend 8" to 12" for better performance.  Reason: angle of incidence at 30 degrees, or so, plus low frequency considerations.  Yes, you will get "some" benefit from 2" or 4", but that's not the objective in terms of desired results.  The comment on rigid insulation is only an example of flow resistivity; a common error is to think more density is better.  Products like Knauf or Safe 'n Sound, etc., work well.  So would a product like GIK 6" Alpha, with an air gap behind the panel.  

One important consideration with side wall/first reflection treatment to note is how wide the treated surface area must be.  Each side wall reflections are generated by both left and right speakers at different locations.  A single 24" panel does not seem to cover the affected area.  I prefer to cover an area 48" x 48" instead.

Finally, budget is a major factor in prioritizing treatment options.  Diffusion is expensive, as is corner bass treatment.  Corner bass was my single most expensive challenge for proper treatment.  You just can't get around it.  Even GIK focused low frequency units are super expensive, just like RealTraps.  Highly effective bass corner traps are just plain expensive from any company.  Even the GIK soffit traps, when used in sufficient number as "some" sort of alternative scheme, are very expensive as a part of the low frequency component.  

When I did my project, I had to accept my budget just did not allow for all the treatment I needed.  Low frequency treatment ate up about 75 percent of my budget, when I first thought it would be about half.  It was over $3,000.  The reality is this:  full treatment of a typical room costs more than most people can afford (at first - or even ultimately, when treated in stages over time).  Thus, people who are serious about it make adjustment and/or compromises they can live with.  Deciding what acceptable compromises are is the key.  The adjustments are commonly to build some acoustic panels, rather than buy them.  These would be the panels which are the easiest to build and which are known effective: 24" x 48" panels.  So, aside from the complex corner panels, the rest can be simple absorption made from readily available material.  In my room, I needed at least 15 panels (after corners - the main priority - were treated): 4 ea. for the side walls, 4 ea. for the rear wall (minimum) 4 ea. for the front wall behind the speakers, and 3 ea. on the ceiling between listening position and front wall. This scheme treated less than 50 percent of the room, which is what I wanted for a more lively room.  I could have easily used more panels on the rear wall.  And, I could have used a cheaper, but effective diffusion treatment on the remaining area of the front wall, and on the ceiling. I could have used 3 panels on each side wall instead of 2 panels.  And, treating side wall - ceiling intersections was a non-starter in terms of priorities and budget. 

I wouldn't listen to much of anything Dennis Foley says. Period. That's not just my opinion.  

@pdreher: 

With respect to GIK vs RealTraps, I was particularly concerned with corner bass traps, not with side wall or ceiling, or even rear wall.  I did not find GIK corner units to achieve the effectiveness needed when calculating for my application.  Otherwise, I find their non-corner units (minimum 6") to suffice for most applications.  Like many engineers, I prefer a high quality diffusion on the rear wall.  However, bass treatment is also necessary on the rear wall.  Thus, I chose to have 6" absorption behind the diffusion panels, as diffusion frequency cut off is rarely lower than 750.  Plus, absorption is cheaper for the added benefit.

I used ATS panels with the coffee bean bag covering in my current room, prior to replacing them with GIK 244, Alpha 4 and Tritraps.   While the ATS https://www.atsacoustics.com/item--ATS-Acoustics-Coffee-Bag-Acoustic-Panel--3001.html satisfied my wife from a WAF standpoint, their performance from an acoustics standpoint was lacking.   The difference in sound quality with the GIK vs. ATS was night and day in my experience.

@nolo and @pdreher  Thank you both very much. These are especially useful.

@papafrog Thanks. A "tunable" idea sounds attractive.

@hilde45

Here is a link data/graph of 4" OC703.  Note random incidence vs normal incidence.  This is just FYI, since it came up incidentally (pun intended).

https://www.gearslutz.com/board/attachments/studio-building-acoustics/502621d1444038910-low-end-resp...

https://www.gearslutz.com/board/attachments/studio-building-acoustics/502620d1444038344-low-end-resp...