The HD1040 one inch exit high frequency compression driver has been designed for use in high quality audio systems.Equipped with proprietary Phase Plug architecture, the HD1040 has been designed to give high level manufacturing consistency and smooth coherent wave front at the horn entrance across the whole working frequency range. The phase plug with its short openings and high flare rate value assures low distortion and demonstrates remarkable improvements in mid-high frequency reproduction. The HD1040 diaphragm assembly is made by proprietary treated Polyethylene material. Thanks to its superior diaphragm dimensional stability (160°C), the polyethilene shows constant behaviour during its whole working life. Moreover, this particular material with its very high value of elasticity modulus, (50% more than standard Mylar and 100% more than polyimide film) is capable of superior transient and intermodulation distortion response. The flat suspension shape is designed to maintain low stiffness and low mid band distortion and response. An edge-wound aluminum voice coil wound on proprietary treated Nomex completes the diaphragm assembly. Thanks to its physical properties, the proprietary treated Nomex former shows a 30% higher value of tensile elongation at a working operative temperature, (200°C) when compared to Kapton. This feature enables proper energy transfer control from the voice coil to the dome in real working conditions. Moreover, this proprietary former material is suitable for use in damp and wet environments. The HD1040 powerful ceramic magnet assembly has been designed to obtain 16 KGauss in the gap within a compact ferrite motor structure.