Recently I bought the upgrade to the new version of IK Multimedia ARC. They say it has better resolution in the bass area. I wanted to find out if this is really true, so I did some measurements with REW before and after ARC2.
Here are some graphs of my room with some absorbers I built (broad band and 2 corner bass traps):
ARC (first version)
A few weeks ago I did measurements with the first version of ARC (1.3.1 to be precise ;-)
Right speaker with ARC:
Left speaker with ARC:
Much better. Overall frequency response and stereo image is better. But the bass area is not flat (due to the modes in my room).
Now the new ARC2. Will it be worth the upgrade price?
Right speaker with ARC2:
Left speaker with ARC2:
The bass frequency response is much better now as you can see and as I can hear ;-) Kick drums are now very punchy and really come from the center now. With ARC it was a little bit like: "yeah, somewhere between left and right" But now it's dead center with punch. I like that!
edit: after a few songs listening to Meshuggah, Slipknot, John Scofield, Destiny's Child: holy shit!!! I love my 'new' bass! For me it's already totally worth it.
Update: here a closer look at the differences between ARC and ARC2. The gray trace is ARC2, 1/6 octave smoothing. I guess you know what the untreated response is ...
Oh, and when you do your ARC measurements this is helpful:
A laser pointer attached to the mic:
(The ARC mic is actually quite usable. This classical guitar piece was recorded with the mic: Classical Guitar Solo 3)
and a piece of cloth with some numbered dots on it: