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

The principle of circuit.
Easiest way is using fuse in series with treble speaker. But we will difficultly select the size or type of proper fuse. If use fast blow fuse may be easy blow unless 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

The both cathode of zener diode ZD1 and ZD2 are connected together, to full wave operation in positive and negative.

The principle are if signal in to 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 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 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. Can be designed to be smaller and packed into a speaker cabinet immediately.

Determining the works point , 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 its.
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 in to 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 = formula1
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 formula2 Size calculated by the AC voltage at the circuit operates with DC power. So the real input voltage of 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. Pleasure of listening to your rising. Since you have this protection tweeters.

The component list.
Resistors 1/2 watts
R1—————-500 ohm
R2—————-27 ohm
R3—————-68 ohm
VR1————–50 ohm
C1—————-0.47uF 50V Polyester.
BD1————–Bridge rectifier 28A 100V
K1—————- terminal block 2 pins
The heatsinks, PCB, Wires,etc.

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