There's that word "faster" again...I keep seeing it pop up in relation to the 600s...I asked this in another thread, but what does it mean?
In addition to what's in the glossary on the link above, here's an example* : play Lil Jon and the bass goes BOOOOOM BOOOOM then on Skrillex it goes WUUUB WUUUB WUUUB. Then when you play, say, Dream Theater the double pedals should
go thudthudthudthudthud, which is generally "fast," but then it goes ThwUuBbThwUuBbThwUuBb instead; or when playing Deftones the kick pedals should
go "THUDww (lyrics) THUDww (lyrics)" but instead go, "THWUUDww(lyrics)wTwHwUUDww(lyrics)w," you're using a headphone or speaker with unnaturally enhanced bass, or it's too much of a complex load for a given amplifier**. Fast is generally the ideal reproduction of the bass drum for those bands, but that's not always clear cut either since sometimes it can be more like "thuthuthuthu" (d's missing) or just THUD, which basically can be too
fast that it either doesn't have enough on the decay on the trailing edge of the note (or it just doesn't reach down low enough on the bass freqs to begin with, if even at the start of the note it seems too weak or not deep enough). That perception on what fast and natural means is basically why people can't agree on whether the K70x or the HD6xx is more natural, which personally is too trivial for me already and just gets in the way of enjoying the music.
*which I hope doesn't confuse you further, but it's worked on my friends, although admittedly they're my former bandmates so they'd be really familiar with instruments outside of recorded material
**this happens less often than people think