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POUL PETERSEN

Electronic design and prototype development.


Limiter threshold calculator for a loudspeaker power limiter.
The two most common causes of loudspeaker damage are thermal overload and mechanical overload.
A power limiter can keep the power supplied to a loudspeaker within safe levels and thereby protect it from thermal overload. To protect a loudspeaker against mechanical overload, it must be driven only within the frequency range it is designed for.
To protect a loudspeaker from thermal overload, the limiter's threshold must be selected to match the loudspeaker's continuous power handling - normally half the power handling stated as continuous pink noise power handling - and the amplifier's voltage gain.

This JavaScript will calculate the required setting for the limiter. All JavaScript code is embedded in this htm file, so you can save it to disk and use it offline.

Any use of data obtained from this program is on your own risk and responsibility.

The calculator is divided into the 3 sections Loudspeaker, Amplifier and Limiter.
The Loudspeaker section calculates the maximum allowed voltage across the loudspeaker based on its nominal impedance and power handling. If the maximum allowed voltage is known, just type it directly into the 'Max. voltage' field. The units Volt, dBV or dBu can be selected for this field.
The Amplifier section calculates the amplifier's voltage gain based on its input sensitivity and nominal output power. If the manufacturer states the amplifier's voltage gain, type this value directly into the 'Voltage gain' field. The units dB or * can be selected for this field.
The program has a database with data for some amplifiers. The data in the list is obtained from amplifier manuals, servicemanuals, sales brochures and from measurements made on amplifiers. Some amplifiers will display the program's default for some parameters (typically a 1 watt output power), if I do not have the information.
The Limiter section calculates the required limiter threshold setting based on the maximum allowed voltage across the loudspeaker and the amplifier's voltage gain. The units Volt, dBV or dBu can be selected for this field. Typing a value into the 'Threshold' field will update the Loudspeaker 'Max. power' and 'Max. voltage' fields based on this value.


Loudspeaker.
Impedance Ohms
Max. power Watt
Max. voltage
Amplifier.
Model
Input sensitivity
Output power Watt
Nominal load Ohms
Voltage gain
Limiter.
Threshold

The unit dBV is dBs with reference to 1 V (0 dBV=1 V). The unit dBu (sometimes called dBm) is dBs with reference to 0.775 V (0 dBV=0.775 V).
This program calculates the limiter threshold as described in Selecting the limiter threshold for a loudspeaker power limiter.
These pages lists the voltage gain for different power amplifiers: AB International, Amcron (Crown), Carver, Cerwin Vega, Dynacord, Harrison, HH Electronics, JBL, NAD.
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Tel/Fax: (+34) 928 152 807, Skype: poul.petersen.gc.
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