The tweeters are in the rear with the rear full range speakers.

The front doors are 6x9 woofers and the ones on the dashboard are midrange (which is odd.. cause usually they're tweeters, right?).

Apparently, this unit uses JBL's Distributed Subwoofer System (DSS), similar to what BOSE has in the new G35. This means, instead of having a dedicated subwoofer speaker, the 4 speakers (door + rear) can receive the woofer signal and are capable of reproducing the lows well.

This is probably the best that I can do explaining it given my limited knowledge of audio equipment.

Mods: EV mod, VVT-i emblem, sport pedals, OEM cargo mat, JDM Prius interior footwell lighting, Sylvania Silverstars 9003ST, DICE iPod kit, OEM all-weather mats, TomTom ONE v2, LED licence plate lights.