The Apollo Upgrade is the ultimate option for Acoustic Elegance woofers. The already incredibly accurate motor design is taken one step further with the use of additional dual Aluminum Faraday Rings that sit on the outside of the voice coil. These additional two rings work in conjunction with Full Copper Faraday Sleeve on the inside of the coil to lower distortion and pull heat from the coil. Very few companies use even a single Faraday ring, while the Apollo Upgrade includes three massive Faraday rings.