The aim of Power Manager is to protect speakers from damage. The object consists of three limiters grouped into two main sub-blocks. The peak-voltage sub-block consists of a frequency-dependent limiter which protects against cone over-excursion. The power-limiter sub-block is made up of a short-term and a long-term limiter, each of which can be configured to attack at a distinct power threshold over an independent time-averaging window.
The power limiter is meant to protect the speaker’s components from overheating. The Power Manager AO has the following additional parameters:
Design Time Parameters
Look-ahead delay [samples]: The fixed delay in samples for the audio signal. This delay improves the response of the peak-voltage limiter at frequencies over 10 kHz.
Tuning Parameters
Power manager exposes below parameters as tuning parameters in GTT for each channel:
|
Name
|
Unit
|
Format
|
Range
|
Default
|
Description |
| Short-term Average Time | s | Float | 0.1 – 100 | 2 | Averaging time-window for the short-term power limiter. |
| Long-term Average Time | s | Float | 0.1 – 100 | 10 | Averaging time-window for the long-term power limiter. |
| Short-term Power Threshold | W | Float | 0 – 100 | 10 | The power threshold over which the short-term power limiter will start reducing gain. |
| Long-term Power Threshold | W | Float | 0 – 100 | 5 | The power threshold over which the long-term power limiter will start reducing gain. |
| Power Attack Rate | s | Float | 0 – 5 | 1 | The rate at which any of the power limiters will reduce gain when the threshold is crossed. |
| Power Release Rate | s | Float | 0 – 5 | 1 | The rate at which any of the power limiters will go back to unity gain when the threshold is not being crossed. |
| Power Depth | – | Float | 0 – 1 | 3.8E-07 | The maximum attenuation allowed for the power limiters. |
| Voltage-Peak Time-Constant | s | Float | 0 – 5 | 0.008 | The tau-constant for the first-order averaging filter used in envelope detection. The envelope level will decay at this rate when the signal-peak is at a lower level. |
| Voltage Threshold Linear Scale | V | Float | 0 – 100 | 1 | The reference threshold from which the contour filters bias the incoming signal. |
| Voltage Attack Rate | s | Float | 0 – 30000 | 2000 | The rate at which the peak-limiter reduces gain when the contoured threshold has been crossed. |
| Voltage Release Rate | s | Float | 0 – 30000 | 500 | The rate at which the peak-limiter goes back to unity gain when the contoured threshold is not being crossed. |
| Voltage Scalar | V | Float | 1 – 100 | 1 | The relation between the configured limiter-threshold voltage and the output voltage of the power IC used. |
In Addition to above tuning parameter Power manger uses below filters to model Peak-voltage and admittance of speaker
Contour Filters: Cascade of three bi-quadratic filters which are used to model the frequency-dependent peak-voltage limit for the speaker.
Admittance Filters: Cascade of three bi-quadratic filters which are used to model the admittance of the speaker. These are used to calculate current consumption and in turn estimate power.
Contour filters and Admittance filters coefficients loaded into DSP/Amplifier can be visualized in SV tree and GTT panel.
|
Name
|
Unit
|
Format
|
Range
|
Default
|
| b0 | – | Float | -100 – 100 | 1 |
| b1 | – | Float | -100 – 100 | 0 |
| b2 | – | Float | -100 – 100 | 0 |
| a1 | – | Float | -100 – 100 | 0 |
| a2 | – | Float | -100 – 100 | 0 |
GTT panel also displays frequency response of filters. Please note that the filter coefficients cannot be tuned from GTT. The filter coefficients are loaded in DSP/Amplifier through a unique API.
Native Panel
PowerManager AO supports native panel. The native panel window has different controls for configuring tuning parameters, fields for displaying coefficients and graph for displaying output voltage/ power. Native panel can be opened by double-clicking on the PowerManager object in the SFD.
