BRIDGE CIRCUIT AND MFB SPEAKER SYSTEM AND SPEAKER

PROBLEM TO BE SOLVED: To provide a bridge circuit which allows for improvement in the detection accuracy of vibration speed of the voice coil of a speaker, in a MFB speaker system.SOLUTION: A bridge circuit for detecting a back electromotive force depending on the vibration speed of the voice coil of a speaker for reproducing voice includes a speaker SP for reproducing voice, a speaker SPD where a vibration part including the voice coil of a speaker having the substantially same configuration and characteristics as those of the speaker SP is still fixed to a fixed magnetic circuit, a resistor R1, and a resistor R2. A series circuit of the speaker SP and the speaker SPD, and a series circuit of the resistors R1, R2 are connected in parallel between the input terminal of drive voltage Eo and the ground terminal, the connection terminal of the resistors R1, R2 serves as the output terminal of a detection voltage V1, and the connection terminal of the speakers SP and SPD serves as the output terminal of a detection voltage V2. 【課題】ＭＦＢスピーカシステムにおいて、スピーカのボイスコイルの振動速度の検出精度の改善を図ることができるブリッジ回路を提供する。【解決手段】音声を再生するスピーカのボイスコイルの振動速度に応じた逆起電圧を検出するためのブリッジ回路において、音声を再生するスピーカＳＰと、スピーカＳＰと略同じ構成・特性のスピーカのボイスコイルを含む振動部を、固定磁気回路部に静止固定したスピーカＳＰＤと、抵抗Ｒ１と、抵抗Ｒ２とを備え、スピーカＳＰおよびスピーカＳＰＤの直列回路と、抵抗Ｒ１および抵抗Ｒ２の直列回路とを、駆動電圧Ｅｏの入力端子と接地端子の間に並列接続し、抵抗Ｒ１および抵抗Ｒ２の接続端子を検出電位Ｖ１の出力端子とし、スピーカＳＰおよびスピーカＳＰＤの接続端子を検出電位Ｖ２の出力端子とする。【選択図】図１