Founded in the early 1980s by Larry Hartke as a subsidiary of Samson Technologies, Hartke designs and manufactures bass amplifiers and, more recently, bass guitars ranging from practice amps to gargantuan performance amps, such as their 810XL bass cabinet (800 watts, 8 ten inch speakers). This was originally custom made for the late great Jaco Pastorius, the godfather of the modern electric bass. Their trademark design is the innovative use of aluminum cone speakers, which produces a sound which is generally preferred over traditional paper cones, especially with funk bassists. Their latest innovation is the Hartke XL-4 bass (and similar basses - the XK4 and XK5).
What makes it so innovative is that the core of the neck and the headstock are totally aluminum. Not only does this result in an incredibly light and balanced instrument, but the amount of sustain (the length of time for which any note will continue sounding) is incredible; think Grand Piano sustain. Sadly, they are not as "mainstream" as similar companies (Ampeg, SWR), and while they're certainly close, it can be somewhat difficult to find a store that carries Hartke.