Loudspeaker protection

[subwerker]

Hi

For cheap loudspeaker protection, I'm considering using a polyswitch wired in parallel with a resistor and a light bulb, as suggested here: http://www.diyaudio.com/forums/solid-state/105504-tweeter-compression-driver-protection-circuit-post1259566.html

My speakers are a pair of 8ohm Dali Concept II, and their recommended amplification is 40 - 120W, as seen in the specifications. My amplifier is 200W in 8ohm.

I would like to protect the whole loudspeaker, by connecting the protection circuit to one of its terminals, as opposed to protecting the different drivers separately.

I'm having trouble determining what resistor and light bulb that could match with these speakers. I have a pair a 2R2 50W resistors - could I use them? What light bulb is best suited in this case?

Thanks!

[CLS]

Have you ever run into some real overload troubles or heard the obviously distorted sounds, or even voice coil rubbing/spider slapping?

If not, you don't need any speaker protection.

If yes, you need speakers with higher sensitivity (usually bigger).

As to the power ratings of those home use hi-fi speakers, you may just ignore them. Your ears and fingers are more than enough for speaker protections.

[subwerker]

Thanks a lot for your answer.

Well, I'm not so proud to say that, but I have blown two pairs of speakers already -- a pair of B&W floorstanders and a pair of JBL bookshelves.

I can perfectly hear when a speaker is being pushed to its limits, but the problem is that I occasionally throw a party at my apartment, and people like to listen to loud music, and drink alcohol.
In such a situation, I tend not to pay attention to how my speakers are treated when I've had a few too many

I wholeheartedly agree about using my ears and fingers to evaluate how a speaker is being driven, but my problem are those uncontrollable alcohol infused parties

I guess I could buy a lot of resistors and light bulbs and try to use my ears to find a matching resistor or light bulb, but I was hoping someone with experience could roughly estimate what I should buy.

The polyswitch I'm planning to use in an RXE250 (http://jaycar.com.au/productView.asp?ID=RN3470)

[CLS]

OK, then.

I think you need some PA speakers for the parties, or something like Klipsch would also do.

Speakers not capable of what you need plus frequently actuated protection will only give you awful performance and interrupted pleasure.

Or, try making a stopper (which can not be obvously seen) on the volume knob.

[mpmarino]

Originally Posted by CLS

OK, then.


Or, try making a stopper (which can not be obvously seen) on the volume knob.

...or it could be an 'electrical stopper'. A temporary RCA jumper between your amp and preamp with resistance installed to lower the gain. If you use a receiver maybe run the RCA jumper from the in and out of a tape loop and turn on tape monitoring?

[CLS]

Neat

[subwerker]

The point of using a polyswitch in parallel with a resistor is to be able to listen to uninterrupted music, and still have some protection if the volume knob gets turned up too much. Of course this is not perfect, but it will at least prevent current overload, and prevent most of the damage.

I thought using a polyswitch was a fairly common thing to do?

CLS, I see you mention Klipsch -- I think they use polyswitches in some of their speakers.

[CLS]

I don't know. I've never used it.

But of course you may try it. It makes sense. When cold, the impedance of PTC fuse (poly switch) is very low which can be seen as wire. When hot (high current), its impedance rises dramatically and then the current would pass through that parallel resistor thus you got protection.

Just don't know how these PTC element affect the audio signal.

[wintermute]

Originally Posted by subwerker

Thanks a lot for your answer.

Well, I'm not so proud to say that, but I have blown two pairs of speakers already -- a pair of B&W floorstanders and a pair of JBL bookshelves.

I can perfectly hear when a speaker is being pushed to its limits, but the problem is that I occasionally throw a party at my apartment, and people like to listen to loud music, and drink alcohol.
In such a situation, I tend not to pay attention to how my speakers are treated when I've had a few too many


The polyswitch I'm planning to use in an RXE250 (http://jaycar.com.au/productView.asp?ID=RN3470)

Used to have this problem myself. I just used the polyswitches, no lightbulbs or resistors required. The way they work is they go open circuit when the current gets too high. Note that the ONLY reason why the current was too high was that the amp was clipping. It was not a problem with the speakers not being able to handle the power... polyswitches work very well as a saftey device to prevent speaker damage from amp clipping in my experience

If you know the true RMS rating of your speakers it should be possible to work out the current rating of the polyswitch you require. ohms law should do the trick here is a post I made some time ago on this --> http://www.diyaudio.com/forums/showt...639#post744639

Tony.

[subwerker]

Thanks everyone.

I guess I need to measure the exact power at which my loudspeakers are overdriven, and buy a suiting lightbulb. Or can I pretty much use any 12V lightbulb?