The term 'CERTAIN SPEAKER' can be solved by the crossword solution 'TWEETER', which is a 7 letter word. A TWEETER is a type of speaker that produces high-frequency sounds, usually in the range of 2, 000 to 20, 000 Hz. It is commonly used in audio systems, such as home stereo systems, car audio systems, and professional sound reinforcement systems. TWEETER speakers are typically smaller than other types of speakers, and they are often used to reproduce higher frequencies, such as those found in cymbals and other percussion instruments.