Dayton ND90-4 3-1 User Manual

A

Klippel Non-Linear Test

Results

LSI (Large Signal

Identification)

Driver Name: ND90-4

Introduction

Large Signal Modeling

t higher amplitudes, loudspeakers produce substantial distortion in the output signal, generated by
nonlinear ties inherent in the transducer. The dominant nonlinear distortions are predictable and are
closely related with the general principle, particular design, material properties and assembling
techniques of the loudspeaker. The Klippel Distortion Analyzer combines nonlinear measurement
techniques with computer simulation to explain the generation of the nonlinear distortions, to identify
their physical causes and to give suggestion for constructional improvements. Better insight into the
nonlinear mechanisms makes it possible to further optimize the transducer in respect with sound
quality, weight, size and cost.

Nonlinear Characteristics

The dominant nonlinearities are modelled by variable parameters such as

Bl(x) instantaneous electro-dynamic coupling factor (force factor of the

motor) defined by the integral of the magnetic flux density B over
voice coil length l as a function of displacement

KMS(x) mechanical stiffness of driver suspension a function of

displacement

LE(i) voice coil inductance as a function of input current (describes

nonlinear permeability of the iron path)

LE(x) voice coil inductance as a function of displacement

More information about these parameters can be found in the article “

Displacement limits”

Nonlinear Parameters

The electrodynamic coupling factor, also called Bl-product or force factor Bl(x), is defined by the
integral of the magnetic flux density B over voice coil length l, and translates current into force. In
traditional modeling this parameter is assumed to be constant. The force factor Bl(0) at the rest
position corresponds with the Bl-product used in linear modeling. The red curve displays Bl over the
entire displacement range covered during the measurement. You see the typical decay of Bl when the
voice coil moves out of the gap.At the end of the measurement, the black curve shows the confidential
range (interval where the voice coil displacement in this range occurred 99% of the measurement
time). During the measurement, the black curve shows the current working range. The dashed curve
displays Bl(x) mirrored at the rest position of the voice coil – this way, asymmetries can be quickly
identified. Since a laser was connected during the measurement, a "coil in / coil out" marker is
displayed on the bottom left / bottom right.

More information regarding Bl(x) and its optimization can be found in the article “

Rest Position”

Optimal Voice Coil

The stiffness KMS(x) describes the mechanical properties of the suspension. It's inverse is the
compliance CMS(x)

More information regarding Kms(x) and its optimization can be found in the article “

Mechanical Suspension”

Adjusting

The inductance components Le (x) and Bl(i) of most drivers have a strong asymmetric characteristic. If
the voice coil moves towards the back plate the inductance usually increases since the magnetic field
generated by the current in the voice coil has a lower magnetic resistance due to the shorter air path.

The nonlinear inductance Le(x) has two nonlinear effects. First the variation of the electrical impedance