The TSW-90 v.4 is a 25.4 cm (10 inch)single driver subwoofer with built-in high-current amplifier and utilizing slotted bass port on the rear.The v.4 version utilizes a totally redesigned amplifier and power boards with higher grade components (capacitors etc.) as well as a heavily modified woofer.The new built-in amplifier delivers slightly higher power output, better efficiency and greater current drive which results in lower distortions, more smooth and flat response and much faster amp operation with significantly reduced operation noises. An integrated clipping limiter maintains the best performance and safe operation of the amp and woofer even at extremely high-volume levels.The redesign bass driver can operate in higher amplitude ranges and can faster react on any changes in the audio signal structure.We changed a regular power cord to a removable IEC type one which provides better power supply filtering and stability and besides gives an option to upgrade your system with a premium audiophile power cable in any time.The TSW-90 v.4 subwoofers deliver the most powerful, deep bass with staggering definition, location and dynamics never met at this price level before. They are the absolute best buy in subwoofers!