speaker protection

[milosus]

Hello everzbody, i looking for speaker protection (dc protection) but without power supply that i can mount directly on speaker , i saw couple of these devices but i cannot find schematic

 

[xrk971]

I remember a passive (no external power) mosfet that would be mounted at the speaker terminal. With DC, it closes the circuit and shunts the amp. I think Apex designed it and Prasi made layout.

 

[Elvee]

For something truly passive, one could think of a bistable relay and a large RC network (but how do you rearm it then?), but it would be rather blunt and primitive.

This protection is not strictly passive, but it almost qualifies since the battery will last forever (and could be helped by solar cells, TEG's or even the audio signal itself), and it allows much more sophistication and discrimination than cruder options:
A.S.P. - Version 2.0

 

[djk]

 

[djk]

Peavey, QSC, etc, all use the same triac + silicon bilateral switch.

2n4992 — Octopart

 

[xrk971]

The data sheet shows two voltages. Does it trip at 1.5v or 7v dc? So that, a triac, and two resistors is all we need?

 

[PRR]

....1.5v or 7v dc?....

If voltage goes to 7V, it "flips" and voltage drops to 1.2V.

7V is 6 Watts of DC heat in an 8 Ohm speaker. This is "negligible" in PA systems (Peavey, QSC) but rather high for hi-fi speakers.

And this plus the triac put a DEAD SHORT on the amplifier. Again the PA amps may shut-down nicely, not all hi-fi amps do.

 

[milosus]

Thank you for helping!
Something like this maybe
SLS Audio D-fend Energy Damping Speaker Protection Circuit
i saw couple of years ago that one guy have protection that is mounted in speaker with relay but without supply and also have trimpot to adjust when realy get start.

 

[Old'n'Cranky]

loudspeaker protection

 

[Kuba_eM]

Some details about triac speaker protection from ESP webpage:
Project 120

 

[djk]

You may add an inline fuse for the triac to crowbar (if your amp is not short-circuit protected).

 

[Bigun]

your output power devices will fuse way before an in-line fuse has even started to shine.

I like Elvee's solution in terms of its' functionality.

 

[Dirttracker73]

I remember a passive (no external power) mosfet that would be mounted at the speaker terminal. With DC, it closes the circuit and shunts the amp. I think Apex designed it and Prasi made layout.

Was it post 2218 in thread http://www.diyaudio.com/forums/solid-state/173462-studio-reference-amplifier-222.html#post4837066

 

[xrk971]

Yes, that was it. It has a couple of BJTs even. Fits inside speaker cabinet and passively powered.

 

[prasi]

Yes, that was it. It has a couple of BJTs even. Fits inside speaker cabinet and passively powered.

here is the sch. it can be mounted on 0.75" speaker binding posts

 

[thimios]

According to Elliot's guides these electrolytics capacitors will be a future problem.
When they dried this circuit will blow up the amplifier without any other reason.
Prasi, you must draw again for not electrolytics here

 

[prasi]

According to Elliot's guides these electrolytics capacitors will be a future problem.
When they dried this circuit will blow up the amplifier without any other reason.
Prasi, you must draw again for not electrolytics here

film cap http://www.farnell.com/datasheets/2...3.1055681548.1508483769-1572543905.1506810295

 

[thimios]

film cap http://www.farnell.com/datasheets/2...3.1055681548.1508483769-1572543905.1506810295

Perfect

 

[milosus]

Thats'it! Thank you!! i will put film caps. Another option it will be with relay and trimpot that i can adjust level when relay will switch off speaker

 

[thimios]

film cap http://www.farnell.com/datasheets/2...3.1055681548.1508483769-1572543905.1506810295

Prasi,you know the next step!