I would describe the 840 as accurate, except for a mid-bass hump (generally appearing in "fun" oriented cans) and somewhat recessed highs. Here's a short description from Tyll's Wall of Fame:
"With a warm and comfortable sound, good isolation, and tank-like build quality, the Shure SRH840 is a top performer at this price point. Semi-pros, musicians, and audio enthusiasts looking for a headphone that will satisfy in moderately loud environments will love the SRH840. Recordists should be aware of the slightly warm tilt to the sound of the SRH840 so as not to overly compensate with eq. Treble response is likewise slightly emphatic, giving these cans a slightly 'happy,' U-shaped listening experience. While these headphone apear rather large and bulky, they are quite comfortable and appropriate for long listening sessions, though they can get a bit warm."
Thanks for the description, should the headphones get warm, is it better if I take it off and let it rest? I've heard the bass on the DJ100s are more rumbling, is this true? I like having a slight rumble to the bass.