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

I went through a very similar situation as you presently have.  Over the course of a couple of years, I read the books and literature, plus participated on Gearslutz acoustics threads.  That was most helpful.  It's good that you've done some REW sweeps; it was valuable to be on Gearslutz in order to properly interpret the various sweeps and to know what they indicated in terms of treatment application.  

Perhaps I misread your approach, but it did not look like you started treatment with very low/low frequency treatment (which you should).  My room is about the same dimensions as your room, except for 9' ceilings.  I ended up treating the corners, floor to ceiling, with RealTraps Mega units, as GIK were not as effective as I needed.  All along  the rear wall (short wall), I use 10" Knauf  mounted in skeletal frames behind RealTraps diffuser panels which are sitting atop their  2' x 2' x 6" absorption panels.  This will give me pretty much what I need for LF control and diffusion.

I moved my speakers closer to the front/short wall to help speaker boundary/LF issues.   I'm testing the first reflection/side wall areas with near diffusers and with combination of diffusion and absorption/range limiting to preserve source content.  On the front/short wall, in addition to the 34" wide corner Mega traps, some additional very effective absorption is necessary; I think you'll find the same.  

Ceiling area just above and toward the front of listening position is something you can determine with additional sweeps and experimentation.

The reason I used RealTraps corner units in addition to their effectiveness and quality build, is that I just did not want to build those myself; predictive software models weren't what I would want to use to build, etc.  However, for non-corners, regular rectangular absorption panels are a piece of cake to build, and pretty cheap.  Knauf from Home Depot comes in pieces that fit just right, at less than 20 bucks a panel, and in thicknesses of like 6" (minimum you should even consider) to over 12".  Knauf has tested very, very well.  A simple skeletal frame is cheap and easy.  You'll save yourself around $1,000 or more for the amount of absorption you will need in your room.  In order to afford the RealTraps units, I had to save money elsewhere.  That said, a few GIK 6" with range limiters was also something I figured in my scheme.  

I suggest you consider calling Ethan Winer at RealTraps for advice.  You can take it or leave it at the end of the day.  He is very nice and quite patient.

Take your time.  Address one issue at a time.  Keep running/interpreting room sweeps/measurements, then move to the next issue as indicated.  Be careful of over absorption or using where not called for.  Move your listening position and speaker distance from front wall as necessary.  

GIK requires full payment on standard production items, while making you wait 8-10 weeks....even for a several thousand dollar order!  The actual production of the product takes about 2 days.  No partial deposit allowed.  Of course, GIK has required full payment up front for years, but the wait used to be about 2-3 weeks.  You'd think with a $54M annual revenue and exceptionally long wait times, they'd modify this policy.  

OTH, RealTraps makes a better product with a three-week wait, so there are choices available.  

Finally, don't use dense/rigid foam products for early reflections/side wall applications; they do not perform well for that application.  Instead, choose a medium weight, medium density, minimum 6" product such as Knauf Ecobatt.

@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.

@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...

@hilde45 :   With respect to your bass issues you are presently seeing on your room sweeps, I guess I'd just say two things:

First, any data must be quite specific (frequency, +-db, left speaker or right speaker, mic placement, listening position in relation to speakers and in relation to room length, and show graphs/waterfall).  Also, I'm assuming you have no corner or front-wall bass traps in place yet?  If you have traps in place, what are they and where they are helps to answer specific questions.  You won't get much good advice with such a general question.  The second thing is partially addressed above: where is the listening position in relation to the front wall (and to the speakers).  At 6.5' from the front wall, I'd assume you are likely 13-15 feet from the front wall.  That would position you at half-way between the front and rear(?).  Or, are you already at the standard 38% recommended to avoid nulls.  No modes on your sweeps?

If what you are seeing on the sweeps before treating is just a couple of nulls, that's exceptional.   Treating is easy at that point.

Are you measuring each speaker separately?  Do they some very close graphs/issues?

Just a general response to a general issue is, bass traps/corner traps can be the product of known specific concerns.  It is pretty straight forward.  However, generally, a corner unit should be 34" wide for effectiveness, and maybe floor to ceiling, maybe not.  They usually won't cure the problems by themselves.   

You can reach out to the acoustics thread at Gearslutz forum if you provide pretty specific data - only then would you get good advice, including type and placement of LF treatment.  You can also tap into some great guys who have tested, built, installed treatment professionally.  But, you have to have all your data (room dimensions, speaker/listening locations, room sweep data).

Here are two links you can use to enhance your ability to use REW; one like is for speaker and listening position placement in real-time, while the other is an REW tutorial by John L. Sayers.  Enjoy!

http://www.johnlsayers.com/phpBB2/viewtopic.php?f=3&t=21122

http://www.johnlsayers.com/phpBB2/viewtopic.php?f=3&t=21122

@hilde45   Ha~  I did duplicate links.  Ugh...

Here ya go; the missing link lol

https://www.gearslutz.com/board/studio-building-acoustics/1305147-speaker-position-help-needed-deter...