| 摘要 |
A speaker including a magnetic circuit formed by an annular yoke and an annular magnet which are concentric around a central axis and face each other across a gap. The magnet includes an N pole region and an S pole region successively arranged along the central axis direction and divided by an imaginary boundary line. At rest, a first coil is positioned in the gap in the N pole region, and a second coil is positioned in the gap in the S pole region. When the coils are driven by an excessively large current, a portion of the first coil moves beyond the boundary line to enter the S pole region, thereby causing a gentle first damping force on the first coil to prevent an excessive displacement. Likewise, the excessive current causes the second coil to move beyond the boundary line to enter the N pole region, thereby causing a second damping force which is opposite in direction to the first damping force. The damping forces limit a displacement range of the coils such that a damper does not collide with the magnet and similarly, the lower end of a bobbin does not collide with a frame of the speaker, thereby preventing collision sounds. The damping forces also prevent excessive stretching or contraction of a suspension, thereby preventing sound distortions.
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