Passive Cardioid Technology™

Fulcrum’s latest innovation, Passive Cardioid Technology™, was developed to overcome the excessive rear low frequency (LF) radiation that is a major performance challenge of many loudspeakers.


The challenge has always been that conventional loudspeakers become progressively less directional with decreasing frequency. At the lowest frequencies reproduced, the sound radiated to the rear of the loudspeaker is approximately equal to the sound radiated forward to the audience (see Fig 1).

Active cardioid arrays are often employed to address undesired rear LF radiation. By requiring additional cancellation loudspeakers, and their associated amplifiers and signal processors, active cardioid arrays are intrinsically cumbersome and costly (Fig 2).

Our game-changing Passive Cardioid Technology eliminates excessive rear LF radiation without the extra cost, space requirements and inconvenience of active cardioid systems – with a single passive cardioid speaker doing the work of an active cardioid array. Fulcrum passive cardioid speakers produce high sound pressure in the forward direction and consistent attenuation in the rearward direction without additional amplifiers, drivers and signal processors (Fig 3).

The subcardioid behavior of Fulcrum Acoustic’s patented loudspeakers is produced by a meticulously conceived acoustical circuit which balances the position of the low frequency driver, the enclosure depth and volume, and a unique arrangement of acoustical elements including rear-mounted ports and calibrated resistive elements.

Passive cardioid technology achieves impressive directional control mechanically within the enclosure in less than half the space required for active cardioid array systems. This allows for cardioid performance in applications that might not otherwise have the budget or space to accommodate an active cardioid array. Our single-amplified, full-range passive cardioid speakers also deliver system cost benefits over traditional bi-amplified active cardioid speaker arrays by enabling up to eight speakers to be driven by a single amplifier channel.

Passive Cardioid Technology was first introduced in Fulcrum’s FL283 Line Array Module, is the basis for our Cardioid Subwoofers product line, and is a technology we continuously develop and evolve into new applications.

Passive Cardioid Speakers Explained

David W. Gunness, Fulcrum Acoustic co-founder and vice president of R&D, was awarded a U.S. patent, formally titled “Passive Cardioid Speaker, No. 10,123,111 B2”, on November 6, 2018. Linked here, Gunness addresses common questions regarding Fulcrum’s innovative new technology.

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