Rob,
I have two rattles in my room that are driving me crazy. One is a vent that goes crazy at around 50Hz and the other I haven't found yet. I think I will create a playlist in iTunes with just that frequency and repeat it until I find it.
Dave, the GIK looks a lot like my Menards special:
![](http://i1302.photobucket.com/albums/ag123/thoscheidt/QRD7%202_zps2oszw013.jpg)
I'll have to see if they list the dimensions on their web site.
These are fairly easy to build but I have been too lazy to finish my writeup on them. They are based off these panels you can buy at Menards. Raven did the calcs in QRDude.
![](http://i1302.photobucket.com/albums/ag123/thoscheidt/Wallboard_zpscbcnoqm4.jpg)
Also Rob, you got me thinking I should bring the skylines I built back into the room. They were on the back wall until I got the styro fractal diffuser array. I am currently trying them at the first reflection point - on the floor.
![](http://i1302.photobucket.com/albums/ag123/thoscheidt/Skyline2_zps6wkufimj.jpg)
I am not sure I like how they sound. They seem to cloud up the soundstage, but it did remind me that these reflection points have an impact. I have DIY acoustic tiles in the drop ceiling at ~the first reflection points above.