Both of my current Steam games are very quiet.  Both Skyrim and Blops 2.

I'm running Windows 7 bootcamped on a late 2009 iMac and using TurtleBeach headphones.  I turned the in-game volume all the way up as well as the computer volume and headphone volume.

The only way I have found to get usable volume is to enter the headphone preferences and turn on "loudness equalization".  This setting has obvious downsides due to artificial equalization of all sounds.

Any help would be appreciated.

BTW, World of Tanks has no issues.

If I remember correctly Skyrim was way too quiet by default and I had to go into the config file and edit it to increase it. Steam should not have any bearing on the volume of games though. It's just an overlay that works with the games, sorta like a frame around a painting and how it doesn't affect the way the painting looks.

Interesting.

I'm not on a Mac but I have the exact OPPOSITE problem. My Steam games are really damn LOUD. Have master Windows volume set to 100% so I can control game volume with my speaker volume knob and I find myself turning my speakers down when playing games then turning them back up when finished so I can hear everything else.

Have you checked your master volume in Windows?

Some headphones won't get loud enough with windows 7.  I never found a fix for this.  Using sennheisers now and they have no problem.

Eta: I had to use loudness equalization while playin skyrim with my old headphones.  Just about blew my ears out every time someone sent me a message on steam.