ESX VX21PRO 53 cm (21) SPL subwoofer 6000w rms 12000w max. 53 cm (21) SPL subwoofer. With the VX21PRO from the VISION VX PRO series, ESX offers a top-class SPL subwoofer. The key specifications alone of this behemoth are more than impressive and will delight SPL fans. Powerful cast aluminum basket with high stability – a must for these massive dimensions. 4 x 150 oz. Quadruple magnet drive with a total weight of an impressive 17 kilograms. Double-stitched high-roll foam surround, which allows a very high deflection of the membrane. Glass fiber reinforced paper membrane with an effective area of?? 1662 cm 2. 6-layer Nomex spider, which ensures good and durable guidance of the membrane. 8-layer 10 cm (4) voice coil (Made in USA), which. Is wound with copper-sheathed aluminum flat wire 80 mm high and is therefore very light and efficient. Voice coil former made of black anodized aluminum. +/- 23mm linear stroke, +/- 35mm X-Max. Integrated 10 mm 2 speaker cable with 1.5 m length. Installation depth 335 mm. Installation opening 495 mm.