Technics SBAS500 Active Subwoofer Adding a subwoofer to a stereo or home theater audio component system yields a richer, deeper and purer bass sound than ordinary speakers can provide 5.5 inch Cone-type Dual Woofers positioned in a downward firing array produce room-filling low frequencies for an added richness that compliments sound without artificial coloration Equipped with its own 100 watt intenal amplifier, there is absolutely no additional strain on your amplifier A low pass filter lets you select a cut-off frequency between 50Hz and 200Hz to help customize a smooth transition for your other speakers A phase switch allows switching between normal and reverse settings to assure the optimum match with room speakers