The HD433 have a very congested and nasal midrange, combined with an unpleasant sibilance caused by a very audible peak going from 2kHz to 4kHZ. There is NO improvement with amplification. Bass impact stops at about 150 Hz and the extension doesn't go any further than about 100 Hz. Really honky headphones with VERY limited treble and bass extension. The build quality is also very flimsy, the plastic used is cheap.

I'd only recommend these headphones for watching TV or listening to AM speech or FM music. Not even suitable for low-rate MP3 setups, since the midrange peak exacerbates the bad ripping quality.

Cheap ? Yes. Better choices out there ? Yes: Koss PortaPro, KSC series, Sony V300, Sennheiser HD212, PX100.