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jaya000 19th July 2007 09:30 AM

tweeter ( Compression driver) protection circuit
To protect tweeter ( Compression driver) of 50~60W from blowing, some transistor circuit is used. can u suggest some?

djk 20th July 2007 03:38 AM

You need a semiconductor called a PolySwitch, an RXE110 is abought right. It goes in series with the hot lead to the compression driver. You will also need a 2R2 15W resistor, wire this in series with an 1156 automotive lamp. Wire this combination in parallel with the PolySwitch.

You can buy this ready made from Peavey for $30, or make it
yourself for less than $5.

djk 20th July 2007 09:26 AM

Burnedfingers 21st July 2007 11:14 AM


You put me on to this a few years back. I've used it in several instances when diaphram replacement was extremely time consuming and dangerous. It works great and protects the drivers. In one church that I used it I haven't been back since to replace any of the drivers.

jaya000 22nd July 2007 03:55 PM

2 Attachment(s)
Here is a circuit suggested by my friend. But it is very old & for small tweeter. I want to use it for 40~60W compression driver. So it need to be modified & more reliable.
Waiting for suggestion & modifications required.

djk 23rd July 2007 12:39 AM

A lot of un-needed fuss.

I would use Schottky diodes for lower noise.

There is another note I can't find that showed adding a lightbulb across the relay contacts. Changing the series resistance higher will allow for a 2" coil, the original was for a 1" coil driver.

I recommend a 211-2 bulb for 1" coils, and an 1156 bulb for 1-1/2"~2" coils.

djk 23rd July 2007 01:47 AM

The relay listed is of course no longer available.

The manufacturer was American Zettler, and their current lineup contains:

9V (nominal) 18.0V (max) 405 (ohms) 6.3V (must pull-in)
pn AZ5X-1C-9DSE or AZ5Y-1C-9DSE

You can cross that to another brand if you like.

While it is only a 1A relay, it can handle 5A with a lightbulb across itself. For midrange use a 15V~18V zener should go across the coil to prevent overvoltage.

jaya000 23rd July 2007 02:38 AM

Thanks djk.
This circuits hv same principle. So better to study during development.

Nelson Pass 23rd July 2007 04:15 AM

Try an automobile parking light in series with the load.


djk 23rd July 2007 08:58 AM

Yep, that's what is in the Peavey gizmo, an 1156 backup lamp.

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