Elements of acoustical engineering (1940) Elements of acoustical engineering elementsofacoust00olso Year: 1940 NONLINEAR DISTORTION 161 The equivalent circuit of the mechanical system, Fig. , shows the effect of the nonUnear element. When the stiffness of the suspension system increases with amplitude, the third harmonic is the preponderant distortion. The wave shape under these conditions is shown in Fig. A distortion frequency characteristic of a diaphragm coupled to a large throat horn is shown in Fig. D. Distortion Due to a Nonunijoryn Magnetic Field in the Air Gap. — Inho
Elements of acoustical engineering (1940) Elements of acoustical engineering elementsofacoust00olso Year: 1940 NONLINEAR DISTORTION 161 The equivalent circuit of the mechanical system, Fig. , shows the effect of the nonUnear element. When the stiffness of the suspension system increases with amplitude, the third harmonic is the preponderant distortion. The wave shape under these conditions is shown in Fig. A distortion frequency characteristic of a diaphragm coupled to a large throat horn is shown in Fig. D. Distortion Due to a Nonunijoryn Magnetic Field in the Air Gap. — Inhomogeneity of the flux density through which the voice coil moves is another source of distortion. The result is that the driving force does not correspond to the voltage developed by the generator in the electrical system. The force, in dynes, developed by the interaction of the current in the voice coil and the magnetic field is / = Bli ~ where B = flux density, in gausses, / = length of the voice coil conductor, in centimeters, and i = current, in abamperes. 20 ?:!3i6 m It) o u X38 -1 = li. ^ 4 1 X 1 Y ; f N AIR GAP \ J LENGTH \ / \ -A 0 .2 .4 AXIAW LENGTH INCHES Fig. Graph of the flux distribution in an air gap. A. Typical distribution of the flux lines in an air gap. B. A voice coil longer than the air gap. C. A voice coil shorter than the air gap. Equation shows that the force Is directly proportional to the current if Bl is a constant. If the Bl product varies with the position of the voice coil the force will not be proportional to the current and distortion will result. A typical flux distribution in an air gap is shown in Fig. A consideration of the flux distribution shows that the Bl product will be
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