Bookshelf Speakers — Joseph Audio PRISM

The Prism is a compact stand-mount from Joseph Audio Inc., the loudspeaker company of designer Jeff Joseph based in Melville, New York, and it sits below the Pulsar2 Graphene in the current range. Jeff Joseph first showed it at CES in January 2014 next to the Profile tower, with a price of USD 3,699 per pair. The stated design goal was to deliver about 80 percent of the Pulsar's performance at half its price, and the name refers to the subtly profiled enclosure walls, which are not parallel. The maker announced the model on its own site in September 2014 and demonstrated it again at CES 2016.

Key specs that matter

The Prism is a two-way ported box with a 1 inch dual-section Sonatex fabric dome tweeter made by SEAS in Norway and a 5.5 inch woofer with an aluminium cone. The crossover point is 2.5 kHz. Joseph Audio rates the listening window within 2 dB from 47 Hz to 20 kHz. Impedance is 8 ohms nominal with a 7 ohm minimum. Each cabinet is 356 mm high, 178 mm wide and 305 mm deep, and the shipping weight is about 10 kg per speaker. Power handling is given as 15 to 250 W. Signal enters via a single set of five-way Cardas binding posts with rhodium and silver plating. Satin white, black and a dark reddish colour are the finish options, and the grille is held by hidden magnets.

Engineering and use context

The filter is the brand's Asymmetrical Infinite Slope type. On the woofer side the low-pass slope reaches roughly 100 dB per octave, while the tweeter is rolled off with a third-order 18 dB per octave filter. Each network is adjusted individually in production, and the maker states that both drivers stay in phase through the crossover region, so the balance is held over a wide vertical and horizontal angle rather than only on the tweeter axis. The woofer was designed specifically for this model with a long throw and a strong motor, and its port fires from the rear panel. In the cabinet the front baffle is wider than the back, and each side panel is split into four planes instead of one flat surface. The aluminium woofer cone is a departure from the cast magnesium cone used in the Pulsar. Joseph Audio does not publish a sensitivity rating for the Prism or for any other model in its catalogue.

Pairing

According to the maker, a true 8 ohm load is less sensitive to the choice of amplifier and cable and works with a broader range of amplifiers, valve designs included. Because there is only one terminal pair, the Prism cannot be bi-wired or bi-amplified.

Alternatives

The Joseph Audio Pulsar2 Graphene is the other two-way stand-mount in the range, pairing a graphene-coated cast magnesium woofer with dual Cardas terminals in a 381 mm tall cabinet.