The 18 Sound iD series transducersare designed to couple perfectly with iPAL Differential Pressure Control technology from Powersoft S.p.A.

The iPAL power amplification module features a zero latency pressure-sensor feedback applying real-time correction to  maximize the select 18 Sound high efficiency transducers for unparalleled output at low frequencies.

Despite the improvements made in design, materials and manufacturing process in the field of low frequency reproduction, the traditional amplifier – loudspeaker approach leaves major issues unaddressed: transducers come with physical limitations and real loudspeakers introduce uncertainties caused by their intrinsically non-linear behavior.
The Integrated Powered Adaptive Loudspeaker system, also known as IPAL®, developed by Powersoft™, is a low frequency reproduction dedicated system that integrates a 8,5kW high-power, high performance switching mode amplifier module – the IPALmod – together with very high motor force electro-dynamic transducers - the 18” and 21” iD family 18 Sound speakers.

18 Sound has specifically developed two iPAL compatible transducers: the 18iD and the 21iD. They both show a 2 Ohm nominal impedance. In order to express the best performance, a pair of the 18iD or 21iD should be connected in parallel when matched to a iPALMod amplifier module. The iD series loudspeakers have been optimized for vented and bandpass subwoofer cabinet designs.
Both iD transducers has been developed after intense FEA and fluid dynamics simulation and testing, in order to extract and dissipate the heat generated by the powerful 2 Ohm nominal impedance voice coil. The 5,3” diameter multi-layer voice coil has been designed using the inside-outside split winding technology, enabling the transducers to handle up to 10000W short term peak power. A special low-density material air-diffraction system acts as a cooling system, increasing the power handling capability and lowering the power compression figure.
The transducer design features include a large displacement suspension system specifically designed for matching the composite fiber reinforced, straight ribbed cone. Thanks to the Triple Silicon Spider (TSS) technology, the 18iD and 21iD transducers are able to control the moving mass with high linearity, showing an exceptional stability of mechanical parameter values in the long term. Bl force factor, as well as all other electro-dynamic parameters, are linear within the working range. This, together with the exceptional high excursion behavior - 70mm before damage, ±14mm linear Xmax - makes the iD series speakers suitable for being integrated in the IPAL system.


IpalMod amp module by Powersoft is characterized by intrinsic stability with impedance variation, as well as effective management of reactive power (back EMF), heralding high performances in any and all load conditions.
The Differential Pressure Control – DPC – is the core technology of the IPAL system, making the IpalMod able to read in real time the transducer cone displacement and to correct its non-linear behavior.

Being the SPL output of any acoustic signal derived from the relationship between the pressure and the acoustical impedance, it’s straightforward to use a direct measurement of such a pressure signal to make the system track a reference target pressure model. A differential pressure sensor measures the difference of pressure between the front and the rear side of the radiating diaphragm due to the acoustic load, and uses this information to correct the behavior of the transducer according to the real boundary conditions. Benefits in terms of predictability of the system response and reduction of sensitivity from disturbing effects could be substantially appreciated.

Thanks to this innovative approach to full boundary conditions feedback processing, the IPAL system dramatically improves the electroacoustic efficiency in terms of high SPL and sonic performance. The DPC approach overcomes the limits of other similar technologies based on the control of the cone speed or acceleration, achieving very high SPL and smoothing the intrinsic transducer tolerances.

On top of these benefits, IPAL system ensures a constancy of the transducer performance over its entire life cycle, as well as balancing the transducer differences with immense benefits in every subwoofer application conditions.

You can find more details here.