Audioengine P4 Premium Passive Bookshelf Speakers A high-performance bookshelf speaker pair with the same great looks and sound as Audioengine's powered speakers. Experience the signature Audioengine sound and quality but without their built-in amplifiers. Beautiful, small, and affordable, P4 is the perfect choice for your living room, bedroom or office and an ideal surround speaker for use with other Audioengine speakers in your home theater or stereo system. Why passive speakers? The P4 passive speakers are full-sounding bookshelf speakers in a satellite-sized package. The goal with P4 was to design a small but powerful bookshelf speaker for people that already have surround receivers or amplifiers and are looking for the same Audioengine sound and quality in a passive loudspeaker. Already have an amplifier? "If you already have an power amp or don't want to give up that big surround receiver then the P4 is for you. The P4 has excellent bass response for its size, which is evident when used either as stereo speakers or as satellite surround speakers in your home theater setup. P4 sounds great sitting on stands, on a bookshelf, or mounted on a wall using the integrated threaded inserts which are compatible with most wall or ceiling mount bracket systems." Part of the Family Audioengine active and passive speaker models share a similar "voicing" and overall tuning so that you are assured a matched system no matter which of their speakers or Audioengine wireless adapters you decide to add to your system. Versatile The P4 passive speakers are perfect for digital hybrid amplifiers (Class-D, Class-T, etc.) as well as most stereo receivers, integrated amps, and tube amplifiers. The P4 has a 4 ohm impedance rating but will sound great when connected to almost any receiver or power amp with 4, 6 or 8 ohm speaker output impedance.