Question about acoustic panels

You are on right track with the thickness, as thin panels only treat high frequencies. 6" panels would be even better. However, you can attain, (to a degree), a better sounding room by just using common furnishings such as pillows, throws and blankets. Also stuffed furniture. These things will quell and/or absorb some of these lower frequencies, improving your rooms response.

From your description, thin wall panels are the wrong way to go.

If your room is a simple shoebox, go here:

https://amcoustics.com/tools/amroc?l=14&w=12&h=9&ft=true&r60=0.6

Then do a few things:

• Move your speakers out of the first 3-4 node areas
• Move your seating position out of the first 3-4 node areas
• Look at the lowest 3-4 nodes and their frequency (more below)

Your first nodes (assuming 9’ ceiling) are 40, 45 and 60 Hz. Those are too low for most panels and even some bass traps so looking at the specs of anything you buy will be important. Measure what’s going on with this in mind. If you find you have big peaks at the listening area these are EASY to take out with EQ.

Alternatively, consider big corner bass traps. At GIK this would be soffit traps, tri-traps but also the monster traps. Keep your 3 modes in mind though. It’s hard to find panels that work below 80 Hz so don’t skimp here. You’ll just suck out the midbass and treble.

Traditional panels will reduce mid-treble, so if you already feel you have too much bass they are going to be the wrong way to go at first. Take as many of the steps above first, then treat with a mixture of absorbers and diffusors.

Now, after you've measured and adjusted you may find your fine with the bass below 80 Hz but are having issues around 80Hz and higher.  Here's where your normal wall panels start to work well.

Remember that absorbers subtract, so if you get panels which reduce a lot of treble your room will sound more present and bass-y.  If you get panels which reduce the mid bass the bass and treble will sound boosted.  Also, include diffusion between your speakers, and don't forget the ceiling especially between listener and speakers.

PS - There’s always someone who says you can’t deal with room modes with EQ. They are ill informed on a theoretical level as well as a practical level. You can deal with peaks alone with EQ. You need bass traps to help deal with nulls though.

Look at the best Stillpoint Apature 2 get 6 for best sound not cheap but the best.