The SP12 sound was less about the bit depth, which mainly determines the max headroom level & came more from the limited sample rate as well as what funkyness the converters may added to the sample.
Lower bit means it'll be easier for sounds to distort when sampling into it, but it ain't that much different between 12 bit with a dynamic range of 72db & 16 bit going up to 96db before it starts to get crunchy. 24 bit (144db) it's more difficult to get that crunch, but luckily Akai added a Amp gain feature in the sample editor which can boost a normalized sample Amp level up 18db & since it's a destructive process you can run your sample thru it again & again until you get the crunch you want.
New MPCs takes more work than a SP to get a dirty sound, but it offers a wider sonic range, especially when you include the other sound shaping tools available like the many different filters & the Drum FX specifically the bit-crush & deciminator. Most seem to sleep on the filters & Drum FXs - don't be one of those people! The SP & old samplers didn't have all these tools so what sound it had or imprinted on samples you & everyone else was limited to that 1 signature sound, maybe that gave people a sense of unity or something by being able to achieve the same sound as their favorite producer.
In a way, older sample-heads are spoiled because the vintage boxes sounded a certain way from the jump, no experience needed, just sample into the box & maybe speed up the source & BAM! These are the ones mainly complaining about the new MPCs being too clean. They are cleaner from the start, which isn't a bad thing. The tools provided if use properly or in some cases intentionally improperly like Warp, can get sonically nasty in a good way, in ways a SP never could. Nostalgia is one powerful drug.
