The tweeter speaker protection circuit

This is The small tweeter speaker protection circuit It can be packed into any speaker cabinet, and does not require a power supply as well.

Normally a high powered audio system. Internal circuitry prevents speaker damage from always packed. It focuses on woofer speaker protection. But when we listen to a lot of trebles. Or high-frequency speakers are often lacking for a long time. Because it lacks dedicated tweeter protection enough.

The principle of the circuit

The easiest way is using fuse in series with the treble speaker. But we will difficultly select the size or type of proper fuse. If use fast blow fuse may be an easy blow unless you can not use the treble speaker. And if use the slow blow fuse it also not rapidly work.

When fuse blow to much change it new one. Which is very time consuming and annoying.

So invent new ways by using two the zener diode. across tweeter speaker as Figure 1. Resistor-R1 value is 2.2 ohms connects to limit current through both ZD1 and ZD2- Zener diode.


Figure 1

Both cathode of Zener diode ZD1 and ZD2 are connected together, to full-wave operation in positive and negative.

The principle is if the signal into too many than the setting ZD1 and ZD2 will works as switches ON. They makes a voltage across the tweeter speaker-SP1 steady in one value.

Most rest voltage will drop across R1 instead, so never cause the tweeter-SP1 too much setting. And if we set the value of ZD1 and ZD2 at 5.6 V the power at speaker-SP1 will get lower than 5 watts, in case that input power of 100 watts.

However, using the Zener diode is limited by the rate of tolerance power is low. Thus the need for a high power voltage control circuit instead.

How does it work

The solution of this problem is Create a voltage control circuit that can support high electrical power sufficiency, as show in Figure 2.


Figure 2 The complete circuit diagram.

The bridge diode-BD1 converts AC signal into DC. This DC voltage is get of BD1 will have 2 feature are the power supply and input voltage, to activate the circuit works.

Both Q1 and Q2 are different transistors type, but is connected in a darlington compound. When the signal reaches to BD1 to transform as DCV. The resistors R1, R2 and VR1 act as the voltage divider circuit, the voltage drop across R2 and VR1 will be voltage activate to Q1 ON.

When Q1 works will be run as if the base and collector of Q2 short circuit, to results Q2 works immediately as the one zener diode. But they has the much higher power rates.

If the incoming signal is not strong enough,the circuit is not working. Using a bridge rectifier converts the input signal into a DC circuit.

Therefore, this project does not need to create any additional power supply. It can be designed to be smaller and packed into a speaker cabinet immediately.

Determining the point of the work, Depending on how you adjust VR1. Should be set from 5-9V can work with the tweeter’s impedance 8 ohms and 3-10 W.

How to build it

Start with a purchased device, then make PCB and assembly equipment as in Figure 3.

For both transistor, Q1 and Q2 installed on heatsinks before, then solder into PCB. If you can not buy by size. May use a 3 mm thick aluminum plate, cut a U (U) is used instead.

Figure 3 Actual-size of Single-sided Copper PCB layout and Component layout for the PCB



Before deployment requires customization. Tools and devices that need include of the power supply adjustable voltage output , multimeter and a resistor of 2.2 ohms 5 W.

If the maximum output of the tweeter speaker of 5 watts at impedance 8 ohms. Can calculate the size of the signal based on the relationship.
V =
By V is the size of the input signals to the tweeters.

P is the maximum output limit.

R is the impedance of the speaker phone.


If it is the size of the signal V is Size calculated by the AC voltage at the circuit operates with DC power.

So the real input voltage of the circuit so must have much more size of signal At first calculated by 1.414 times.

When this DC voltage input to make the circuit work with the 1.414 x 6.3 = 8.9V.

Tuning circuit in Figure 4 from the power supply input voltage 15-20 V.Then adjust VR1 to set the multimeter to measure DC voltage reading is 8.9 V, just as it shall be completed. The protection tweeters installed in the cabinet immediately.

the-application and setting

Figure 4

Do not be worried that the treble speakers will damages. When you listen to music at a specially pitched. The pleasure of listening to your rising. Since you have this protection tweeters.

The component list

Resistors 1/2 watts
R1: 500 ohms
R2: 27 ohms
R3: 68 ohms
VR1: 50 ohms
C1: 0.47uF 50V Polyester.
BD1: Bridge rectifier 28A 100V
Q1: BD139
Q2: TIP2955
K1: Terminal block 2 pins
The heatsinks, PCB, Wires, etc.

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I always try to make Electronics Learning Easy.

I love electronic circuit. I will collect a lot circuit electronic for teach my son and are useful for everyone.
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