SELENIUM RPST400 -Watt -Channel Studio Subwoofer, Selenium RPST400 replacement diaphragm for the Selenium ST400 bullet tweeter. Use a genuine factory replacement diaphragm to repair a blown or damaged Selenium high frequency driver. Selenium RPST400 replacement diaphragm for the Selenium ST400 bullet tweeter. Use a genuine factory replacement diaphragm to repair a blown or damaged Selenium high frequency driver. Selenium RPST400 replacement diaphragm for the Selenium ST400 bullet tweeter. Use a genuine factory replacement diaphragm to repair a blown or damaged Selenium high frequency driver.