Resource to calculate, building and measuring Hi Fi Loudspeakers and more...

zondag 20 januari 2019
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 Loudspeaker PTC Overload Protection Calculator

PTC thermistors can be used as current-limiting devices for circuit protection, as replacements for fuses.
Current through the device causes a small amount of resistive heating. If the current is large enough to generate more heat than the device can lose to its surroundings, the device heats up, causing its resistance to increase, and therefore causing even more heating.
This creates a self-reinforcing effect that drives the resistance upwards, reducing the current and voltage available to the device.

Mounted in series to the speaker, they are well suited to protect speakers against overload.


  Power handling in W:  
  Impedance in Ohm:  

The used PTC should have :  Amps
According to the manufacturer the fuse switches off after 3 seconds at   Watt

Input guide lines :
  • Bass drivers the rated power handling may be entered
  • Tweeters with 10 mm dome diameter ca. 1 Watt
  • Tweeters with 19 mm dome diameter ca. 4 Watt
  • Tweeters with 25 mm dome diameter ca. 8 Watt
  • PA-Tweeters half the rated power handling

This kind of protection is mostly used for Car-Speakers and sometimes for PA-Speakers.

Personally i would not use it for HiFi Speakers.