Michael Plessmann's penchant for unusual solutions is in particular evident in the mid-woofer unit. The Supravox has an exponentially shaped, lightweight paper cone, and is said to have a high sensitivity and low distortion. These ought to be further reduced by removing the dust cap. The small pressure chamber in front of the driver helps to improve linearity and also eliminates resonance and distortion, which is an unintentional by-product of the surround. An opening in the rear wall of the cabinet, which has approximately the same diameter as the driver, allows it to breathe freely, while its activity is not even restricted by a crossover. The designer wants to get by with as few components as possible in and around the signal path. That's why the Pirol gets away without any drain circuits and impedance linearisations.

The high frequencies are entrusted to an Air Motion Transformer from German specialist Mundorf, which is assisted by a Tractrix horn – in the test sample made of solid wood – that allows for a low lower crossover frequency. The crossover features a slew rate of six decibels and is built with Mundorf capacitors. Silver/gold and silver/gold-oil types are used. The required value is realised by a parallel connection. A ribbon tweeter is located on the rear, covering the frequency range from four to 22 kilohertz, in order to provide more airiness in the sonic image. Its level can be adjusted depending on individual tastes or room situations.

If the outward dimensions of the speaker have to be kept at a reasonable room friendly level without waiving the frequencies down to 30 Hertz by at the same time following up with the efficiency of 97 decibels specified by tweeter and mid-woofer, then an active solution taking care of the low frequency range is indispensable. Soundspace Systems settled on two side-radiating twelve-inch woofers with carbon fibre cones provenient from the professional sector. DSP technology is used for both linearising the frequency response of the drivers in their sealed enclosure below 100 hertz and implementing the low-pass filter for coupling the mid-woofer. The DSP operates at a sampling rate of 96 kilohertz and could also be used to defeat room modes. Following Michael Plessmann's purist approach, we admittedly dispensed with room calibration in my listening room. Notwithstanding the many adjustment possibilities offered by the DSP, the developer contented himself with a filter of first-order for the lows as well. With a slope of only six decibels, the two woofers still radiate energy far into the fundamental range – a truly unconventional solution. As already mentioned before, the bass range is managed by a 500 watts Class D amplifier originating from the PA sector. So, there is absolutely no need to worry about control respectively damping factor and reliability.

Soundspace Systems manufactures the internal cabling, which is individually adapted to each driver, by hand. The standard version features solid wiring made of cryogenically treated copper, while a silver version is also available as an extra-cost option. Solid wood is used for routing the cables. Even though I probably may have given a lecture on only less than half of the information provided to me on the Pirol so far, it should have become clear that there is almost no detail that Michael Plessmann hasn’t pondered about – and that in some areas he has chosen solutions way beyond from the mainstream.