Here are some links I had saved when researching this a while back:
Some of them sell the insulation and provide kits for DIY.
http://www.readyacoustics.com/http://www.realtraps.com/http://www.atsacoustics.com/http://www.gikacoustics.com/If using the passive panels it is best if you leave an air gap between the panel and the wall. The more panels the better. And it is better to use the denser OC 705 vs the OC 703, and thicker is better.
Keep the back open and let the waves pass through. Most people I think make a smaller frame at the back and then attach the fabric to that frame with staples or upholstery tacks.
Ethan Winer is associated with Realtraps, but he published this article in 1995 in Electronic Musician.
http://www.ethanwiner.com/basstrap.htmlThese panels are sealed and work using a vibrating front panel concept. Inside is a fiberglass panel that dampens the vibration. You might think about this design as it might be more effective with your cement wall. He uses alternating different wood panels for differing lower frequency ranges.
Here is another room mode calculator. This one is more visual.
http://www.hunecke.de/en/calculators/room-eigenmodes.html