The 1770s have something like 5 dB less treble than the 1990s, normalized to 1000 Hz. They're either missing treble (except the peak) or have too much mids depending on where you normalize.

In my experience the 1770s are duller sounding than the 1990s without EQ, but the 1990s can also be actively unpleasant on treble-hot content.

If you're using a normal stereo output (no DSP), use Stereo (or 'headphone' if available) output. If using one of the virtual surround systems (either software or hardware), set to 7.1.

If you're just plugging the headphones into your desktop tower or monitor, it's probably just normal stereo.