You are here: Home / Know-how / Measurements / Signal and System Analysis / Magnitude and phase response

# Magnitude and phase response

Characteristics:

KLIPPEL R&D System KLIPPEL QC System
Complex Transfer function TRF, LPM, DIS QC Standard: SPL, SPL+IMP, IMP, MSC, MST, MTD
Total phase (unwrapping, without constant time delay) TRF, LPM, DIS QC Standard: SPL, SPL+IMP, IMP
Minimal-phase, excess-phase response TRF
Polarity TRF QC Standard: SPL, SPL+IMP

Nyquist plot

TRF

The transfer behaviour of a linear system between input and output can be described by a complex transfer function H(jω) in the frequency domain. The transfer function is independent of the spectral properties of the stimulus as long as the system behaves linearly and as long as the input and output signals are measured at sufficient SNR. The real and imaginary part of the transfer function H(jω) can be displayed as a Nyquist plot. Alternatively, the complex transfer function can be represented as magnitude and phase response. Simultaneous acquisition of input and output signal is recommended for measuring phase responses. A linear system can be described as a combination of three subsystems (minimal-phase subsystem, an all-pass and a subsystem having a constant time delay). The minimal-phase response can be calculated from the amplitude response by using the Hilbert transform.

## KLIPPEL R&D SYSTEM (development)

Module

Comment

Transfer Function Module (TRF)

TRF is dedicated for the measurement of the complex transfer function by using a sinusoidal sweep (chirp) as stimulus and performing a two-channel data acquisition. In the small signal domain the transfer function (amplitude and phase response) is independent on the properties of the stimulus (spectral properties). A variety of tools for post-processing is provided (impulse response, windowing, smoothing, time-frequency transformation, …).

Linear Parameter Measurement (LPM)

LPM uses a multi-tone complex as stimulus which is perfect for measuring the electrical impedance, the mechanical transfer function Hx(f)=X(f)/U(f) between displacement and voltage and the sound pressure response Hp(f) in the small signal domain.

3D Distortion Measurement (DIS)

DIS performs a steady-state measurement of phase and magnitude of the fundamental component referred to the internal stimulus. This module is perfect to investigate the dependency on the measurement amplitude.

Scanning Vibrometer (SCN)

SCN measures the mechanical transfer function between loudspeaker terminals and the laser displacement sensor using a sweep with amplitude profile (amplitude increases by 10db/octave to ensure high SNR at high frequencies).

Near Field Scanner (NFS)The Near-Field-Scanner 3D offers a fully automated acoustic measurement of direct sound radiated from the source under test. The radiated sound is determined in any desired distance and angle in the 3D space outside the scanning surface.

## KLIPPEL QC SYSTEM (end-of-line testing)

Module

Comment

SPL Measurement Task (in QC Standard)

SPL measures the amplitude and phase response of the electrical or acoustical input signal using a sinusoidal sweep as stimulus. The sweep may vary versus frequency according to an amplitude profile or a user defined sweep speed to ensure sufficient SNR of the input signals and optimal resolution of the transfer function at particular frequencies.

Impedance Task measures the electrical impedance and phase using a sinusoidal sweep or a multi-tone complex as stimulus.

Motor Suspension Check (MSC) MSC dispenses with an additional small signal measurement but measures the nonlinear parameters at the rest position x=0 while operating the transducer in the large signal domain using an ultra-short multi-tone stimulus. It measures the electrical impedance and phase using multi-tone complex as stimulus.
Multi-Step Task (MST) Multi-Step Task performs a steady-state measurement using a single-tone or two-tone stimulus where the voltage and frequencies can be varied in each step.
Multi-Tone Task (MTD) Multi-Tone Task measures the amplitude response using a multi-tone complex as stimulus.

## Templates of KLIPPEL products

Name of the Template

Application

TRF Scanning Cone Vibration

Manual scanning of cone vibration using a laser sensor with high cut-off frequency (>15 kHz)

TRF sensitivity (Mic 2)

Calibration of the microphone at IN2 using a pistonphone

TRF SPL + harmonics

Standard measurement for fundamental component (SPL) and harmonic distortion

TRF SPL + waterfall

Sound pressure level and cumulative decay spectrum

TRF true acoustical phase

Total phase without time delay

TRF cumulative decay

Cumulative spectral decay

DIS SPL, Harm protected

Harmonic distortion measurement with protection

DIS X Fundamental, DC

Fundamental and DC component of displacement

Diagnost. MIDRANGE Sp1

Comprehensive testing of midrange drivers with a resonance 30 Hz < fs < 200 Hz using standard current sensor 1

Diagnost. RUB&BUZZ Sp1

Batch of Rub & Buzz tests with increased voltage (applied to high power devices)

Diagnostics MICROSPEAKER Sp2

Comprehensive testing of microspeakers with a resonance 100 Hz < fs < 2 kHz using sensitive current sensor 2

Diagnostics TWEETER (Sp2)

Comprehensive testing of tweeters with a resonance 100 Hz < fs < 2 kHz using sensitive current sensor 2

Diagnostics VENTED BOX SP1

Comprehensive testing of vented box systems using standard current sensor 1

Diagnostics WOOFER (Sp1)

Comprehensive testing of subwoofers with a resonance 30 Hz < fs < 200 Hz using standard current sensor 1

Diagnostics WOOFER Sp1,2

Comprehensive testing of subwoofers with a resonance 30 Hz < fs < 200 Hz using current sensor 1 and 2

IEC 20.6 Mean SPL

Mean sound pressure level in a stated frequency band according IEC 60268-5 chapter 20.6

IEC 21.2 Frequency Range

Effective frequency range according IEC 60268-5 chapter 21.2

IEC 22.4 Mean Efficiency

Mean efficiency in a frequency band according IEC 60268-5 chapter 22.4

Standards:
IEC Standard IEC 60268-5 Sound System Equipment, Part 5: Loudspeakers
AES2-1984 AES Recommended practice Specification of Loudspeaker Components Used in Professional Audio and Sound Reinforcement

Papers and Preprints:
A. Farina, “Simultaneous Measurement of Impulse Response and Distortion with a Swept-Sine Technique,” presented at the 108th Convention of the Audio Eng. Soc., J. of Audio Eng. Soc. (Abstracts), Volume 48, p. 350 (2000 Apr.), Preprint 5093.

G. B. Stan, J. J. Embrechts and D. Archambeau, “Comparison of different impulse response measurement techniques,” J. of Audio Eng. Soc. 50 (2002), pp. 249–262.

E. Mommertz and S. Müller, “Measuring impulse responses with digitally pre-emphasized pseudorandom noise derived from maximum-length sequences,” Applied Acoustics 44 (1995), pp. 195–214.

S. Müller, P. Massarani, Transfer-Function Measurement with Sweeps, J. of Audio Eng. Soc. 2001, June, Volume 49, No. 6, pp. 443-471.

D. D. Rife and J. Vanderkooy, “Transfer-function measurement with maximum-length sequences,” J. of Audio Eng. Soc. 37 (1989), pp. 419–443.

To top