As most of you know, I've gone graph crazy.
Not sure what it is, but there is something that is interesting about improving your room response and overall sound.
Before I get started, I want to thank "Bridgman" for helping me become an Excel expert on graph plotting.
Ok, so I've been spending some time lately on various websites reading about the topic of improving your room response by using a combination of bass traps and mid-high treatments. Many believe this type of setup is mainly for recording studios, when in fact the same rules apply to a HT environment. There are tons of great websites out there on this subject. Audioholics even has some great articles on bass traps and acoustic treatments. Another great starting point is http://www.ethanwiner.com/acoustics.html
or reading some of the other articles by Ethan's company at www.realtraps.com
I decided to take the DIY route as usual to save a buck. What I really appreciate about people like Ethan from RealTraps, Bryan from SensibleSoundSolutions, and Glen from GIK Acoustics, is that they were willing to give me advice on building my own treatments using some of the same materials they use, versus trying to talk me into buying from them.
Based on my research I decided to purchase some Owens Corning 703 Rigid Fiberglass board from a local insulation distributor. This is a popular product that has been proven to have great absorption properties when installed correctly. Many people use foam products, but if you look at the stats, they just can't compare to Rigid Fiberglass board, Mineral Wool board, or cotton. The 703 I purchased came in 2' x 4' x 2" thick sheets. Many people will double these up and straddle a corner which provides good results for bass trapping, just ask Royce73. However, an even better method is to use superchunks, which basically are triangles that fill the entire void in the corner.
The OC 703 is very easy to cut. Just make sure you have some gloves on as it can make you itch, just like regular fiberglass. For starters you cut the 2' x 4' piece in half. This gives you two 2' x 2' pieces. You then cut these each diagonally to make triangles which are 24" x 24" x 34". Many people use this size for their corner chunks, however, I decided to make another cut to those pieces which gave me 17" x 17" x 24". This size worked better next to my screen and gave me room for my m60's.
Here is a picture of some of the precut OC703.
Once they are all cut, you basically stack them in the corner. I built a frame out of some 1 x 2 pine, and used general purpose velcro to attach the black felt I purchased at Walmart.
For low bass frequencies the material is not as important as it is for higher frequencies. With the higher frequencies you don't want a material that will reflect the sound. A good test is if you can see some light passing through or if you can feel your breath through the material you'll be fine. Muslin is another material often used.
Anyway, I know Bridgman told me not to worry about graphs, but I could not help myself. I didn't figure I would see much improvement just by adding two rear wall bass traps. In reality, it is best to have all your corners treated with some form of bass trap, this can include corners where ceilings meet walls also. I would then move onto treating some of the first reflection points with mid-high frequency traps. But one thing at a time.
Sooooooo without further ado.....Here is my most recent graph. In both situations I used the Real Traps test tone CD which covers from 10hz upto 300hz in 1hz increments. The master volume was set at 70dB's per the instructions. Prior to the tests all my speakers were calibrated for SPL, Delay, and dB levels using the Denon built in mic and setup. In addition, I verified the dB levels with my SPL meter prior to starting. M60's were set to small with a crossover of 80hZ.
Overall, I feel there is some good improvement if you compare the before/after plots across the entire graph. You can see the severe dips I had around 145hz and 235hz have improved. In addition some of the higher peaks around 40hz, 55hz, and 80hz, have been reduced slightly.
The most important thing that really suprised me is the sound has improved just with two rear traps. I've been listening to a variety of cd's in my collection and I am being 100% honest that I truely hear a positive difference. The bass is much tighter and individual notes are clearer and easier to hear versus the "one note bass" that some experience, especially in the lower range.
Sorry this has been such a long post, I hope some of you can provide some positive feedback for me.
Thanks for listening, Randy