CN1173105A - Pseudo-zero impedance loudspeaking technology and loudspeaking system - Google Patents

Abstract

The invention relates to an improvement of loudspeaker technology and a loudspeaker system using the technology, which measures a physical quantity related to the movement speed of a loudspeaker diaphragm in real time, the physical quantity and an audio signal picked up by the loudspeaker system control the movement of the diaphragm, so that V = KU is satisfied between the speed V of the diaphragm and the audio signal U picked up by the loudspeaker system, wherein K is a constant. The invention makes the loudspeaker system have more ideal frequency response characteristic, namely, reduces the frequency selectivity of the loudspeaker system, and makes the loudspeaker system have good sound reducibility.

Description

Pseudo-zero impedance loudspeaking technology and loudspeaker

The loudspeaker that the present invention relates to a kind of improvement of loudspeaking technology and use this technology.

For widely used loud speaker, audio signal voltage directly is added in the coil two ends, because there is the impedance of loudspeaker coil, makes system have frequency-selecting, and the frequency response of loudspeaker is undesirable.In order to overcome this defective, people adopt a plurality of loud speaker frequency divisions to raise one's voice and method such as additional frequency compensating circuit, but effect is still undesirable.

The Driving technique that the purpose of this invention is to provide a kind of loud speaker makes loudspeaker have comparatively desirable Frequency Response, promptly reduces the frequency-selecting of loudspeaker, makes it to have good sound-reducing.

Another object of the present invention provides the loudspeaker of using said method.

The solution of the present invention is: measure the physical quantity relevant with the loudspeaker vibrating diaphragm movement velocity in real time, this physical quantity and loudspeaker picked up audio signals are controlled the motion of vibrating membrane jointly, make between the speed V (t) of vibrating membrane and the loudspeaker picked up audio signals U (t) and satisfy V (t)=KU (t), wherein K is a constant.

The physical quantity relevant with the vibrating membrane movement velocity can be the motional electromotive force that coil moves in magnetic field in the said method.

The loudspeaker of using said method is: an input of voltage comparator is as audio signal input end, its output connects speaker drive and signal sample circuit through power amplifier, this circuit connects another input of voltage comparator through feedback circuit, and the output of loud speaker and speaker drive and signal sample circuit links.

In loudspeaker, the electrodynamic loudspeaker coil impedance causes the frequency-selecting of loudspeaker.Proof is if coil impedance is zero below, and then loudspeaker does not have frequency-selecting.If certain electrodynamic loudspeaker coil impedance is zero, then:

Em is the coil motional electromotive force in the U=Em=2 π rN|B||V| formula, and r is a coil radius, and N is a coil turn, and B is a magnetic flux density.So coil speed V=U/ (2 π rN|B|) ... (1) magnetic field is to the active force of coil

F=2 π rNI|B| like this, power of loudspeaker output

P=FV=IU ... (2) as seen, noenergy loss in the conversion process of energy.

Investigate the electroacoustic power conversion with the forced vibration model below.Because loud speaker transducing in one-period $W=m{\∫}_0^T\mathrm{fVdt}=\left[{\∫}_0^T(d^{2}X/{\mathrm{dt}}^2+2\mathrm{\βdX}/\mathrm{dt}+{\mathrm{\ω}}_0^{2}X)\mathrm{Vdt}\right]\·m$ X is a coil displacements in the formula, and β is the system damping coefficient, and T is the system vibration cycle.Get f (t)=f _oExp (j ω t), then average transducing power is in the cycle $\stackrel{\‾}{P}=\∫2\mathrm{\βm}{(\mathrm{dX}/\mathrm{dt})}^2\mathrm{dt}/T=\mathrm{\β}{\stackrel{\‾}{V}}^2\·m=L\stackrel{\‾}{V^2}-----\left(3\right)$ Wherein m be vibrating membrane and coil quality and; L=β m is a constant.Can see that by (1), (3) formula the zero impedance loud speaker does not have frequency-selecting.In view of the average energy current density of sound wave is directly proportional with the mean value of air vibration velocity squared, the diaphragm face air velocity equals the vibrating membrane vibration velocity, and (3) formula result, and we have reason to think that the zero impedance electrodynamic loudspeaker is desirable loud speaker.

The present invention measures in real time the physical quantity relevant with the vibrating membrane movement velocity, and this physical quantity is fed back, and controls the motion V (t) of vibrating membrane jointly with system picked up audio signals U (t), makes V (t)=KU (t), and wherein K is a constant.Be that loudspeaker is provided with frequency-selecting, have desirable sound-reducing.Described device is obtained the physical quantity of a reflection loudspeaker vibrating diaphragm movement velocity by speaker drive and signal sample circuit, coil induced electromotive force for example, this physical quantity is sent into voltage comparator through feedback circuit, with the audio signal of sending into voltage comparator through the power amplifier control loud speaker, thereby reach purpose of the present invention.

Fig. 1 is a structure principle chart of the present invention.

Fig. 2 is an embodiment of the invention circuit diagram.

As shown in Figure 1, an input of audio signal AB input voltage comparator 1, the voltage comparator output connects speaker drive and signal sample circuit 4 through power amplifier 2, loud speaker SP links with it, and the output of speaker drive and signal sample circuit 4 is connect another input of voltage comparator by feedback circuit 3.

Among Fig. 2, M constitutes voltage comparator, and Q1, Q2 constitute power amplifier, and R2, R3, R4, L constitute speaker drive and sample circuit, and M2, M3, M4 constitute feedback circuit.

Audio signal is held input system by AB, and the current amplifier that is made of Q1, Q2 behind M1 carries out power amplification; Constitute the bridge-type dual-sampling circuit by R2, R3, R4, L and loud speaker SP, the d point voltage $\mathrm{Ud}=\frac{R3}{R2+R3}\mathrm{Uc}$ Be reference voltage; The f point voltage $\mathrm{Uf}=\frac{R4+\mathrm{j\ωL}}{R4+\mathrm{Rs}+\mathrm{j\ωL}+\mathrm{j\ωLs}}(\mathrm{Uc}-\mathrm{Em})$ Be the velocity correlation signal, Rs, Ls are respectively resistance and the inductance of loud speaker SP in the formula.Getting R2=R3, R4=Rs, L=Ls then has Ud=Uc/2, Uf=(Uc-Em)/2.

Ud is through the influence of M3 buffering to reduce to sample to circuit; Uf is anti-phase through the inverter buffer that M4, M5, M6 constitute.If the input impedance of M4 is infinitely great, then

(Ud-Ug)/R7=(Ug+Uf) so/R8 gets then Ud-Uf=2Ug of R7=R8

Ug=(Ud-Ug)/2=Em/4 has so just generated moving living signal Ug; Ug enters the motion that audio signal that M1 negative terminal and AB import is controlled the electrodynamic loudspeaker vibrating membrane jointly after M2 buffering.

If AB incoming level U is higher than the moving signal Ug that gives birth to, then comparator M1 output output high level makes Uc=+E, and the rapid forward of the vibrating membrane of loud speaker SP quickens or anti-phase deceleration; The motional electromotive force Em of loudspeaker coil raises with the variation of coil speed; Ug increases; Comparator negative terminal input current potential raises.When Ug rises to when equaling high level U, vibrating membrane speed stops to change.On the contrary, if U is lower than Ug, comparator M1 output low level makes Uc=-E, and the motional electromotive force Em of loudspeaker coil reduces with the change of coil speed; Ug decreases.When Ug reduces to when equaling U, vibrating membrane speed stops to change.Because the vibrating membrane accelerating time is extremely short with respect to the audio signal cycle, we can think that AB end input voltage U equates with the total maintenance of Ug.Because Ug=Em/4, Em=2 π rN|B|V is so the pseudo-zero impedance loudspeaker satisfies under audio conditions

U=KV like this, circuit has realized that pseudo-zero impedance raises one's voice.

Claims (3)

1, a kind of pseudo-zero impedance loudspeaking technology, it is characterized in that measuring in real time the physical quantity relevant with the loudspeaker vibrating diaphragm movement velocity, this physical quantity and loudspeaker picked up audio signals are controlled the motion of vibrating membrane jointly, make between the speed V (t) of vibrating membrane and the loudspeaker picked up audio signals U (t) and satisfy V (t)=KU (t), wherein K is a constant.

2, loudspeaking technology according to claim 1 is characterized in that the physical quantity relevant with the vibrating membrane movement velocity is the motional electromotive force that coil moves in magnetic field.

3, a kind of loudspeaker of using said method, an input that it is characterized in that voltage comparator is as audio signal input end, its output connects speaker drive and signal sample circuit through power amplifier, this circuit connects another input of voltage comparator through feedback circuit, and the output of loud speaker and speaker drive and signal sample circuit links.