Abstract: A speaker system that has a first speaker containing a first speaker unit in a first cavity and a second speaker containing a speaker unit wherein the crossover frequency of the first speaker and second speaker is f.sub.cr : 1.4.ltoreq.Q.sub.1,.ltoreq.10, f.sub.1 <f.sub.2, f.sub.1 .ltoreq.f.sub.cr .ltoreq.f.sub.1 .times.{(Q.sub.1.sup.2 +1.2.times.Q.sub.1)/(Q.sub.1.sup.2 -2.5)}.sup.0.5 .times.k, l.ltoreq.k.ltoreq.{(Q.sub.1,/(Q.sub.1,-1.4) }.sup.2.5, where the fundamental resonance frequency of the first speaker is f.sub.1, the resonance sharpness is Q.sub.1, and the fundamental resonance frequency of the second speaker is f.sub.2.

Abstract: A bass reproduction speaker apparatus of the present invention includes: a cabinet with an opening, having a division member inside thereof; a speaker unit disposed at the division member; a passive radiator disposed in the opening; an amplifier for driving the speaker unit; a detector for detecting a vibration of a moving system of the speaker unit; and a feedback circuit for feeding back an output signal from the detector to the amplifier.

Abstract: After a silicon nitride film (2) is etched by using a first resist pattern (3A) as a mask before coating a second resist (4) superposing on the first resist pattern (3A), a surface layer portion of the first resist pattern (3A) is subjected to a plasma treatment by using oxygen (O.sub.2). A properties changed layer in the surface layer portion of the first resist pattern (3A) is removed or modified to improve the adhesion between the second resist (4) and the first resist pattern (3A), and the stripping of the second resist (4) is prevented.