tweeter ( Compression driver) protection circuit

[jaya000]

burnedfingers

The 1156 is a simple back up bulb in an automobile rated at 21 watts lamp power.

The specification shows that it is 2.1 amps.
So even we calculate safely 13.2V x2.1A = 27.72W. i.e. 28 Watts.

 

[djk]

The bulb draws more current at 13.2V, the spec is for 12.8V.

 

[jaya000]

In the circuit posted by phase_accurate :
The input device BC 546 can be changed to 2N5551.
I am thinking of changing the output darlington pair to darlington TIP 127 of TIP 147. TIP 147 or TIP 127 will also not need heatsink?
waiting 4 suggestions :

 

[jaya000]

phase_accurate,
I assembled ur circuit.
I just changed the output darlington pair with TIP 127.
I hv to add 100ufd condensor in parallel to relay coil to avoid chattering.
Otherwise circuit worked ok.

 

[phase_accurate]

I hv to add 100ufd condensor in parallel to relay coil to avoid chattering.

Mine worked OK without cap but this might depend on the relay's properties. I am pleased that you got it working.

Regards

Charles

 

[jaya000]

How to select the cutoff voltage of relay & how to set it?
I am thinking of using ac voltage ( 50hz) as input to the circuit as source.

 

[bear]

Of course one could simply use a limiter on the feed/amp that runs the compression drivers set up so that it never exceeds the power rating of the drivers, and never clips the amps...

Otoh, running the compression driver with highly compressed signal due to the limiter running hard all the time at or near the max level for a sufficient period of time will also tend to cook the VC...

So, don't do that. 😉

_-_-bear

 

[jaya000]

Thanks bear.
But i am talking about setting the circuit. To give input to the circuit, can i use normal AC 50hz as voltage source?

 

[phase_accurate]

But i am talking about setting the circuit. To give input to the circuit, can i use normal AC 50hz as voltage source?

Do you want to use the mains to set the cutoff-point ? If so, then keep in mind that you should do this with an isolated variac. do not even think of plugging it into the mains directly. But you would still encounter problems setting the point properly since this TWEETER protection circuit is not meant to be run at 50 Hz !

Why don't you use the amp that it is inteneded to be used with to set the cutoff-point ?

Regards

Charles

 

[jaya000]

Thanks phase_accurate,
I will use variac ( auto transformer) plus a step down transformer. So the input will be isolated.
Then i will check the AC input with the meter & will set the trigger point accordingly. As this is to do with few component value changes, hence selecting this AC voltage 50hz source. The protection circuit is going to operate on DC so there is no question of any frequency.
I think this will be ok as per ur guidance.

 

[phase_accurate]

The protection circuit is going to operate on DC so there is no question of any frequency.

I thought you were going to use it for a TWEETER !? 😕

Regards

Charles

 

[jaya000]

I was talking just about setting the circuit operationg point (Relay operation) before connecting to tweeter.

 

[phase_accurate]

In this case I would provisionally use a larger timing cap and set the working point with AC (the circuit is making "DC" out of it anyway).
Depending on the relay that you are using you'd have to change the emitter resistor of the darlington. Don't forget to calculate the losses in the darlington since it might need some cooling - depending on the current through the relay coil.

Regards

Charles

P.S. Here you can see one of my ringradiators packed into a small box (top right) together with the protection circuit and the crossover:http://www.diyaudio.com/forums/showthread.php?postid=1266503#post1266503

 

[jaya000]

Thanks phase_accurate for info. Happy to know about ur whole project.

Specially ringradiators :
interesting! i will like to know more about this.
hv u designed the mid horn urself?
what type woofer enclosure? is it wbin?

In this case I would provisionally use a larger timing cap

U means to say that the value of 1ufd to be increased.

 

[phase_accurate]

regarding the cap: I'd place a 47 uF in parallel to the 1 uF while testing the thingie with 50 Hz.

Regading the Horns:

Woofer: EV Eliminator copy using a Fostex L467.
Midbass: My own (well almost !) using a Fane Studio 10M
Mid-High: Peavey. IIRC the horn was called FH-1 and the driver SP22 but I am not sure anymore.
Tweeter: Ringradiator PR130 by Audax (bloody expensive 25 years ago, one is lost unfortunately).

The system was used for disco in small to medium venues. In the latter case there were two additional TL4025 bass-bin copies used - stacked upon each other and placed inbetween the rest of the system.

Regards

Charles

 

[jaya000]

bear:

Of course one could simply use a limiter on the feed/amp

The circuit consumes lot of current after conduction. The heatsink becomes hot. So i was thinking of using current limiter in the circuit so that it will not consume high current & load the amplifier. Most important is if the output transistor fails then the purpose of circuit becomes useless. This means the circuit will current controlled one.
Suggestions in the matter r highly appreciated.

I saw one speaker power, volts & current calculator at edaboard.com.
It might be useful.
Link :
http://www.edaboard.com/ftopic266410.html
But u hv to register to download it.

 

[jaya000]

bear:

Of course one could simply use a limiter on the feed/amp

On the diyspeakers.net forum today i read the following about tweeter protection :

the Peavey solution is one of the interesting ones.
It uses a poly switch that sends the juice
through a 100watt 5-ohm resistor followed by a couple of light bulbs.
People STILL manage to blow the Peavey
compression drivers up. My guess is most of them
are running sound from stage and never hear the
mains enough to know it they are punishing them (and the audience).

The person for whom i am going to make is expert in blowing tweeters. I think that this problem is everywhere. Hence I thought for more development.
The circuit consumes lot of current after conduction. The heatsink becomes hot. So i was thinking of using current limiter in the circuit so that it will not consume high current & load the amplifier. Most important is if the output transistor fails due to high current, then the purpose of circuit becomes useless. This means the circuit will be current controlled one. Reading on this topic today
Suggestions in the matter r highly appreciated.

 

[phase_accurate]

The circuit consumes lot of current after conduction. The heatsink becomes hot. So i was thinking of using current limiter in the circuit so that it will not consume high current & load the amplifier.

Do you mean the protection circuit is consuming a lot of power and the amp's heatsink is getting hot ? I don't think so except you use some humunguous relay.
I think you are suffering from what I already hinted at: Don't fully disconnect the load from the crossover !!!!!!!!!! An LC crossover without load is a series resonant circuit. Driven at its resonant frequency it acts almost like a short circuit !!! Some amps do not like that !

Most important is if the output transistor fails due to high current, then the purpose of circuit becomes useless.

Which doesn't matter at all since it is not needed anymore as soon as the amp gets unable to send output power to a load.

Active limiter circuits that the input of power amps (usually integrated into active controllers) are of course the most elegant solution.

Regards

Charles

 

[jaya000]

Phase accurate,
I am sorry. I forgot to add the schematic of the another circuit i was working on.
I am now working on one more circuit after ur circuit became successful.
I am working on 2nd circuit of the attached page with darlington circuit.
But i am going to change it to pnp -npn combination.
The problem mentioned was of this circuit.

 

[phase_accurate]

Aahh a Zener - diode emulation. Looks like Elektor ?! Quite clever - but you will burn quite some power if you want to protect a high-power tweeter. You will not get around a large heat-sink. And you may use it only after a voltage divider otherwise you risk cooking your amp.

Regards

Charles