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Loudspeaker Response


The Loudspeaker Response block evaluates the performance of a loudspeaker based on chirp measurements. The block calculates the loudspeaker basic loudspeaker performance responses including: impulse reponse, frequency response, phase response, group delay response, and THD response. You have the option of smoothing if desired.

KxNMxNMxNFxNFxNFxNFxN1xNImpulse ResponseReferenceSignalFrequency ResponsePhase ResponseGroup DelayTHDSystem Delay


Reference Reference is the reference chirp inputted to the loudspeaker. The recommended reference signal is a loopback of the outputted voltage. You can input N inputs with M length at once.

Signal signal is the measured chirp signal. You can input N inputs with M length at once for example if you have repeated measurements.


Impulse Response is the windowed impulse response with K samples according to the property Time to nearest reflection.

Frequency Response is the magnitude response of the windowed impulse response with desired number of FFT bins and Octave smoothing.

Phase Response is the phase response of the windowed impulse response.

Group delay is the group delay response of the windowed impulse response.

THD is the Total Harmonic Distortion response of the windowed impulse response, based on THD order number of harmonics.

System Delay is the total delay between 0 s and the time of the peak of the impulse.


Pre-Peak time5 ms
Time to nearest reflectionโ˜ 10 ms
Distance to nearest reflection
FFT Binsโ˜ 16384
Octave Smoothing1/12
THD Orderโ˜ 10
Chirp Timeโ˜ 4.5 s
Chirp Start Frequencyโ˜ 20 Hz
Chirp End Frequencyโ˜ 20,000 Hz

Values with โ˜ can receive external input.


Name specifies the name of the block.

Pre-Peak time#

Pre-Peak time is a specified time that determines how much time you want to have before the peak of the impulse. To get the delay of the system look at the output System Delay The Pre-Peak time is specified in order for you to get a consistent impulse length on every measurement.

Time to nearest reflection#

Time to nearest reflection specifies the time delay between the direct impulse and the first reflection. If the time is higher than the delay of the first reflection then it will affect the evaluation of the loudspeaker performance.

Distance to nearest reflection#

Distance to nearest reflection can be set instead of time to nearest reflection. The distance is the same as you would measure the length between the loudspeaker and a reflection object.

FFT Bins#

FFT Bins is the desired resolution of the frequency responses. The number of FFT Bins must be higher than the number of samples K in the Impulse Response.

Octave Smoothing#

Octave Smoothing is how much you want the frequency reponses smoothed. You can choose from 1/1 band octave smoothing to 1/48 band octave smoothing, or no smoothing at all.

THD Order#

THD Order is the number of harmonics you want to calculate for the THD response. Default is up to the 10th order.

Chirp Time#

Chirp time is the overall time of the reference chirp.

Chirp Start Frequency#

Chirp start frequency specifies the start frequency of the reference chirp.

Chirp End Frequency#

Chirp end frequency specifies the end frequency of the reference chirp.


Inputs specifies the number of inputs the block requires. This cannot be changed.