Small but very useful. This circuit provides protection to your tweeter specially when they are always driven near the maximum level.
The first circuit uses a simple bulb as a load. This bulb will glow when the signal going to the tweeter reaches a certain preset threshold level.
The bulb functions like a positive temperature coeficient (PTC) resistor - meaning its resistance increases proportionally to its temperature.
At around 5.5, the transistor 2N3055 will conduct and shorts the tweeter's input line to ground, thereby preventing the overloading of the tweeter.
The second circuit is an improved version. A fixed resistor replaces the bulb and the switch transistor is a darlington pair with a delay capacitor.
The circuit still functions like the first circuit. However, due to the capacitor, the circuit will not react to a single overload peak.
This circuit is usually installed inside high power boxes like those in disco applications where equipments are commonly driven to their maximum ratings.
Parts Placement Layout
Electronic Circuits volume 1.0 - Circuit Nr. 9
The complete data of the electronic circuit described above can be found in the following book and is available from Amazon.com.
Click on the image to view the book.