Abstract: A truncated, open top, pyramid housing is provided containing a downwardly propagating woofer mounted near the base of the pyramid; a forwardly and slightly upwardly propagating tweeter mounted on the front side of the pyramid; and a pair of rearwardly propagating, crossed polarity, mid-range speakers mounted on opposed sides of the pyramid housing. The push-pull propagation between the opposed mid-range speakers, within a single housing, and similar cooperation between stereo loudspeaker pairs, provides a generally phase distortion free, wide dispersion sound circulation. A polarity switch is provided for establishing the desired cross-phase relationship. The nonparallel side configuration of the housing reduces internal resonance by preventing standing wave formation. The open top functions as an unidirectional port which also reduces internal resonance. The upward portion of each sound cycle is guided out of the speaker housing towards the ceiling by the funneling action of the slanted, tapered sides.

Abstract: An interchangeable head system for an ink jet printer of the asynchronous, volume displacement droplet ejection type in which the print head is mounted on the print head carriage in a manner such that it may be readily detached and replaced with another head; the print head mounting allowing for adjustment of the distance from the print head nozzle to the print receiving medium. The ink supply connection to both the print head and the ink supply container includes means for automatically closing off the ink supply line to prevent either the loss of ink or the introduction of air into the container, supply and print head when either the print head or the container is removed from the system. The print head includes an ink supply pressure sensor for sensing the changes in pressure in the system and a valve operated by the sensor to supply ink to the system upon reduction of the pressure below a predetermined level.