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Compression driver protection?

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palesha

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I have seen the circuit attached is used in crossover. It is used for compression driver protection. I like to know does it really work?
 

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What an odd circuit?

There should be no positive and negative because audio is AC, not DC.

R1 is permanently in series with the speaker which will reduce the power by 1/4 and can't be good for the damping factor.

When the breakdown voltage of D1 to D4 is exceeded, the TRIAC is triggered which connects R3 across the speaker, reducing the power by half.

This seems like a bad idea, a DIAC and potential divider should be used instead of D1 to D4, the TRIAC should short the speaker directly and R1 should be a PTC resistor to limit the current.
 
Did anyone notice that the TRIAC is shorted out by the connection between R3 and R5? Also, the bridge arrangement of diodes will pass nothing unless the PIV of one of them is exceeded. Since they are not drawn as zener or avalanche breakdown types, it is going to short out permanently on about the second or third cycle.
 
What an odd circuit?

There should be no positive and negative because audio is AC, not DC.

It's common to mark speaker terminals as such, in order to maintain correct polarity, just as speakers are marked as well.

R1 is permanently in series with the speaker which will reduce the power by 1/4 and can't be good for the damping factor.

Not a problem on a high frequency unit like this, only on bass units.

When the breakdown voltage of D1 to D4 is exceeded, the TRIAC is triggered which connects R3 across the speaker, reducing the power by half.

This seems like a bad idea, a DIAC and potential divider should be used instead of D1 to D4, the TRIAC should short the speaker directly and R1 should be a PTC resistor to limit the current.

I would suggest the ciruit is drawn wrongly, the TRIAC appears to be connected wrong, and the diodes can't be just diodes, but probably zeners in series with diodes.
 
It's common to mark speaker terminals as such, in order to maintain correct polarity, just as speakers are marked as well.
Yes, I suppose it makes sense to use the same notation., not that it matters: the circuit can be connected either way.

Not a problem on a high frequency unit like this, only on bass units.
Why is that?

Surely it has resonance to?

Fair enough it might not be noticeable but wasting half the power isn't a good thing, the listener will just turn the treble up a bit causing the amplifier to work harder.


I would suggest the ciruit is drawn wrongly, the TRIAC appears to be connected wrong, and the diodes can't be just diodes, but probably zeners in series with diodes.

That makes sense but I would've put the zeners back-to back.
 
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Yes, I suppose it makes sense to use the same notation., not that it matters: the circuit can be connected either way.

Yes, as long as you keep both the same.

Why is that?

Surely it has resonance to?

You don't understand what damping factor is do you?.

Doesn't apply to tweeters because they are connected through hi-pass crossovers anyway.

Fair enough it might not be noticeable but wasting half the power isn't a good thing, the listener will just turn the treble up a bit causing the amplifier to work harder.




That makes sense but I would've put the zeners back-to back.

They are back to back.
 
It's common to mark speaker terminals as such, in order to maintain correct polarity, just as speakers are marked as well.



Not a problem on a high frequency unit like this, only on bass units.



I would suggest the ciruit is drawn wrongly, the TRIAC appears to be connected wrong, and the diodes can't be just diodes, but probably zeners in series with diodes.

I agree with all posted above. The circuit probably does work....but has been badly drawn and understood by the OP. Stuff does sort of make sense if you think about it....and change components around and remove short links on the Triac.

My take....original PCB Circuit copied from working speaker protection PCB.

And then a really bad job done to draw the Schematic from a PCB.

Any comments??
 
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It is normal for a tweeter, especially a very sensitive compression driver that feeds a sensitive horn, to be fed from an attenuator. Then its output level will match the output of a woofer that needs to move a lot of air so it is not sensitive.
 
It is normal for a tweeter, especially a very sensitive compression driver that feeds a sensitive horn, to be fed from an attenuator. Then its output level will match the output of a woofer that needs to move a lot of air so it is not sensitive.

That makes sense: woofers are very inefficient, especially compared to horns.
 
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