The Bk5.1iS is a shielded 5-1/4" two-way bookshelf speaker.  It uses some exceptional drivers, that are available at a very affordable price.  The woofer is a 5-1/4" unit from Dayton Loudspeaker (available only from Parts Express).  It features a coated paper cone, rubber surround, and shielded magnet structure.  The tweeter is also from Dayton Loudspeaker.  It uses a 1" titanium dome and is ferrofluid cooled and completely shielded.  Both drivers offer good power handling and very quick sound.  As you will note from the price list, they are both very reasonably priced.  The enclosure was made with particle board for the top, bottom and sides, and a high quality plywood for the front and back.  Particle board doesn't route well, so plywood is a better choice for the baffle if the drivers are going to be flush mounted.  The crossover is a prebuilt 6dB/octave system that is built into the terminal.  The crossover frequency is around 3500 Hz, which puts little strain on either the woofer or tweeter.

These speakers were intended to be used in conjunction with a powered sub, so they were designed to have good mid and high reproduction.  They are a very forward speaker.  The mids and highs are shockinly clear and detailed, with unbelievable depth.  While not specifically designed to have good bass performance, the Bk5.1iS offers surprising low frequency performance.  The system can play down into the 50 Hz range.  Obviously a 5" driver won't provide slamming bass, but in a smaller room, the Bk5.1iS will provide a very full sound, even without the use of a subwoofer.