The accuracy of SW + Jig is really quite amazing. It should be noted however that it takes a bit of tweaking
before getting measurements this good. I found that using the right value for your sound card impedance (entered in SW)
is important in getting improved accuracy. Some people just use the default value, which is probably perfectly ok for
loudspeaker measurements anyway.
And finally I should note the sound card used, which is the Hercules Game Theatre XP.