Visaton bf 45 4ohm aluminium coned mini speaker with high output visaton bf 45 4 ohm p the bf 45 is a 4 5cm 1 8 inch miniature speaker with aluminium diaphragm and transparent plastic basket with two mounting holes the balanced frequency response and very good low range reproduction make it an excellent choice for applications where slim construction and good music and speech reproduction are requested p visaton bf 45 4 ohm aluminium coned mini speaker with high output