ND25FW-4 1" Soft Dome Neodymium Tweeter with Waveguide 4 Ohm. ND25FW-4 1" Soft Dome Neodymium Tweeter with Waveguide 4 Ohm. Waveguide loaded 1" treated silk dome. Waveguide provides controlled directivity and higher efficiency. Low Fs of 1,350 Hz can accommodate crossovers as low as 2,500 Hz. Includes foam gasket to ensure a good seal to your enclosure. High-strength neodymium motor with heatsink and ferrofluid cooling. Standard 104 mm diameter faceplate for easy integration into many existing systems. The Dayton Audio ND25FW-4 tweeter features a unique integrated round waveguide faceplate that provides a controlled directivity transition at high frequencies, reducing the effect of room reflections on the speaker's tonal balance. Unlike conventional flat-faceplate dome tweeters whose directivity does not match the midwoofer driver near the crossover frequency, the ND25FW-4's waveguide is curved to maintain consistent directivity at the transition. The waveguide also acts as a low-compression horn, lowering distortion. Waveguide-loaded dome tweeters are embraced within the industry for providing directivity control and mild horn loading without the negative effects of compression loading such as impulse smear and throat distortion where high levels are not needed. The waveguide profile used in the ND25FW-4 provides a minimum dispersion angle of about 90 degrees, and maintains directivity control to about 2,000 Hz, but the round waveguide will install easily into the same 104 mm standard tweeter cutout used commonly by dome tweeters with larger ferrite motors. Specifications: Power handling: 20 watts RMS/40 watts max, VCdia: 1, Le: 0.04 mH, Impedance: 4 ohms, Re: 3.2 ohms, Frequency range: 2,500-20,000 Hz, Fs: 1350 Hz, SPL: 91 dB 1W/1m, Dimensions: Overall diameter: 4.09, Cutout diameter: 2.875, Depth: 1.57.