In recent years, there has been a flurry of interest in so-called cardioid speakers for the home and studio, with the charge led by manufacturers such as Dutch & Dutch and Kii Audio. But what exactly is a cardioid speaker, and what are its benefits?
Cardioid speakers are a type of directional speaker designed to project low- to mid-frequency sound in a specific dispersion pattern (radiation of sound into the three dimensions of space) that resembles the shape of a heart or cardioid (hence the root “cardio-”, as in, for example, “cardiovascular”).
Not that there is anything special about a heart-shaped dispersion pattern in particular. Rather, the great advantage of cardioid speakers is that they are able to project most of their sound forward, toward the listening area - even at mid-low frequencies - and not backward, toward the wall, where it will tend to reflect and then recombine messily with the sound coming directly from the speaker - as occurs, for example, when a conventional (non-cardioid) speaker is placed near to the wall behind it.
If this is difficult to conceptualise, a helpful analogy may be to think of a stone dropped in a still pool, causing waves to ripple out in all directions. If the stone is dropped near one end of the pool, waves will bounce off that wall and quickly recombine with the waves emanating directly from the stone’s landing place - in a very messy, chaotic manner. This is analogous to what happens when soundwaves bounce off the wall behind a conventional speaker and then recombine with the direct sound travelling from speaker to listener: the two sound sources recombine to form a tonally chaotic mess.
Now imagine a (not-in-reality-possible) cardioid stone. When it is dropped in the water, its ripples project outward in only one direction. The water on the rear side of the stone will remain perfectly calm so that, if the stone is dropped close to a pool wall, waves do not reflect back off that wall to recombine with the waves emanating directly from the stone’s landing place. In other words, there will be no messy chaotic recombination of waves in the preferred direction.
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Returning to the real world of speakers - where cardioid radiation is thankfully entirely possible - this means no strong reflections off the wall behind the speakers and, consequently, no low- to mid-frequency tonal mess caused by the recombining of direct and reflected sound at the location of the listener.
Cardioid speakers achieve this by employing multiple woofers arranged such that the forward-facing woofer(s) are complemented by one or more side- or rear-facing woofers, whose phase (timing) is carefully tuned to ensure that, when their output is combined with the output of the forward facing woofer, that all-important cardioid, forward-projecting dispersion pattern results. Engineering a quality cardioid speaker is neither easy nor cheap, but the sonic benefits in a typical room, particularly one in which the speakers must be placed relatively close to the wall behind them, are significant.
At phoniq, we employ cardioid technology in many of our advanced designs, particularly for clients who need their speakers to be placed close to a rear wall. Contact us if you’d like to find out more.
