As far as I know, Pete Rock and Primo both use or have used at one point (most likely their "Golden Era" records) the "Low End Theory." They sample the loop that they are using into an Akai S950 and filter it to get the bass. Not sure what they do after that in terms of further processing and effects. But that's the basic jist of it.
Pete Rock claims to have been the first to discover the filtering technique while playing around with the S950's filter. But Easy Mo Bee also claims to have been the first to filter for the bass. I read in an interview that Mo Bee also usually EQ's his sound sources before he samples them.