To develop this new Illusion Audio speaker line we combined our decades of experience manufacturing high-end audiophile speakers with our passion for maximum performance mobile audio. The development process covered several years and literally months of listening to each individual model to fine tune musical quality and durability. We applied the highest available technologies in construction materials, Finite Element Analysis engineering and manufacturing to develop speakers that are compact and lightweight for easy installation without making any performance compromises. Our artistic design team has paid careful attention to aesthetics, as we feel they are beautiful speakers too! Aluminum coated injection polypropylene cone with rubber surround powder coated steel basket Midbass: Free Air Resonance: 31.36 Hz Nominal Impedance: 4 Ohms Sensitivity 2.83 v @ 1 meter: 87.2 Outside Diameter: 312 mm Mounting Hole Diameter: 280 mm Mount Depth: 154 mm Recommended Sealed Enclosure Volume: 1.0 cubic ft Maximum Linear Excursion: ± 14 mm Tweeter 25 mm aluminum dome 4 ohm Outside Diameter: 48.2 mm Mounting Hole Diameter: 43.5 mm Mount Depth: 11 mm Crossover: Bi Amp 12 dB crossover Tweeter overload protection Dimensions: 131 x 84 x 38 mm Titanium-coated injection polypropylene cone with rubber surround Powder-coated steel basket 26 mm voice coil Driver Specifications: Fs: 99.26 Hz Re: 3.36 Ohms Qms: 6.23 Qes: 1.14 Qts: 0.97 Le: 0.12 mH Vas: 2.23 liter Mms: 6.85 gram Cms: 375 uM/Newton BI: 3.55 Tesla-M SPLref: 87.6 (2.83 volts at 1 meter) Sd: 65 sq cm Xmax: 2 mm Xsus: 9 mm Nominal power: 40 Watts Maximum Power: 80 Watts Outside Diameter: 102 mm basket + 130 mm ears Mount Hole: 94.5 mm Mount Depth: 52 mm Weight: 567 grams