Cost to treat a room?

$700-900, assuming you buy used. As newbee remarked, the challenge is to find out what the problem is. Lastly, every room needs to be treated as perfect rooms only exist for perfect people, all can be improved.

Above 100 Hz not all that difficult or pricy but for smaller rooms is worthwhile. In an earlier small(er) room setup I used 4 Corner Traps and 4 Tune traps together (cost was around 350-400) rather successfully (some of them now not needed and are for sale!). Experiment and Experiment!

GIK is great for the money. Real traps start getting pricey but they are well built, their web site is worth a visit just for the info on room treatment they provide.

Just start with the mirror points on each side wall between you and the speakers. Second is treatment behind the speakers.

One thing to think about is that you can't EQ bass room nulls, and using an eq to reduce peaks does not sound the same as reducing them with room treatments...a treated room will have faster time response.

So you may want to consider doing a low frequency treatment in corners behind the speakers in addition to the EQ.

Newbee, Good advice.

One way could be to buy and read a couple of books (ej, Everest's and Floyd's books) to understand what's going on, get an SPL meter from Radio Shack ($60?) and a CD with test tones and start experimenting with home furnishings, comforters, etc to further understand what might work in your room. Then you could either buy or DIY treatments (receipes available at AAsylum, for instance).

I'm going down this path and while it's been a lot of work it is being fun and I'm learning a lot as I go. It's likely the cheapest albeit most time-consuming approach.

My two cents. enjoy!