As stated, EQ 600 offers 3 individually selectable frequencies (5, 10 and 15) and all five frequencies in Multi mode.
EQ 800 offers 5 individually selectable frequencies (5, 10, 15, 20 and 40) and all five frequencies in Multi mode.
It's in the manual (Page 29, fine print under the coloured graph explains 20 and 40 not available on the 600 but that the Multi-IQ frequencies shown apply to BOTH the 600 and 800) and has been discussed/argued on several forums I'm a member of since it's release.
The differences between the 600 and 800 (aside from this) include:
- 600 has no Gold Mode.
- 600 supplied with wired headphones (but has wireless capability the same as the 800). The 800 is also supplied with the Wireless Module, allowing you to use wired headphones to connect wirelessly. You also get a second charging cable (could be handy down the track if one breaks...who knows what they'll charge for replacements).
- 600 has backlight on or off, whereas the 800 has brightness adjustment.
- 600 has no User Profile save setting, the 800 does.
- 600 doesn't have Threshold Pitch adjustment, the 800 does.
- 600 has Recovery Speed settings of 1, 2 and 3 which equate to 2, 4 and 6 on the 800. The 800 has 8 Recovery Speed settings, meaning it has more adjustments within the same range as the 600, as well as extra settings above the 600.
- Iron Bias settings are the same as stated for Recovery Speed.
- 600 only has Ferrous Tone Break adjustment. 800 has four Tone Break adjustment settings.
Not sure if that's all the differences, hope it helps.