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How to protect my Infinity Primus 250 tweeters...

Mike Massa

Mike Massa

New Member
I have acquired a pristine set of Infinity Primus 250 loudspeakers, that are basically a two-way setup. I've read that a common problem with the tweeters is that they can blow quite easily. I want to protect these tweeters and would like anyone's input on a possible resistive L-pad configuration (maybe 5 ohms in series and then a maybe 15 ohm across the tweeter?) or maybe a 12V automotive bulb in series with the tweeter, etc. Any ideas are welcome, thank you!
 
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Second time today I'm linking this thread.

ETA: you'll want to fuse just the tweeter, not the entire speaker, and calculating the power that the tweeter can handle may be difficult. I couldn't find any indication anywhere of its power handling (it's possible, although unlikely, that the power handling is marked on the back of the tweeter). Be aware that the power handling of a tweeter is usually only a few watts, since high frequencies require very little power (most of the power is used by the woofer). Barring any other info, I'd purchase an assortment of low-current fuses, then use the reverse Calvin and Hobbes method (see below): start at 1 watt (note: not 1 amp; you'll have to calculate the amperage based on the tweeter impedance), then if you blow it, move up to 2, then 4, then keep going until you're listening at what you think is the highest level you think you'd ever want without blowing the fuse.

Probably more important is to ensure that you're not driving your amp into clipping (I found a few threads that indicated this was what caused the tweeters to fail).

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Mike Massa said:
From a picture of the 250 crossover I found on eBay, it doesn't look like there is a poly switch.
Click to expand...

Hard to tell, the small brown “box” under the blue and green wires towards the front edge could be one. Would have to see from a different angle.
 
I personally don't see that, but who knows. I think if there was a protective device, the tweeters wouldn't get blown and we wouldn't be having this discussion, lol. AIl I see are inductors, capacitors, and a large white 10W and 5W resistor. I sure appreciate your help!
 
I dont see any poly switch in that photo.

If you are not running them at ludicrous volumes you probably wont have an issue.

I had a pair of Crescendo 3008s or 3009s, (i don't remember) with poly switches and I only tripped them once the entire time I owned them.
 
Yeah, I didn't either. Anyway, I think you're right because from what I remember reading - the tweeters only popped when someone was really cranking them up. I plan to be pretty gentle with these. Thank you!
 
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