Fountek NeoCD2.0 5" Ribbon Tweeter Super strong Neodymium magnets 5" sandwich ribbon diaphragm Built-in impedance conversion transformer Recommended frequency range 2,500Hz to 40kHz Thin enforced sandwich ribbon diaphragm guarantees a high degree of signal fidelity and broad frequency response. Low distortion factor, good power-handling capabilities, high linear impedance and amplitude frequency response and the broad frequency response range. Flat impedance from 1,000 to 40,000Hz Warning: Ribbon tweeters should always be used with a passive crossover! The ribbon is a dead short to your amp. Do not test without a capacitor. Do not use an electronic crossover without a capacitor (we use 20+ mfd).