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Fuses for Peavey tweeters?

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Fuses for Peavey tweeters?

Postby cunningtim » Sat Sep 12, 2020 2:04 am

I’ve recently come into possession of 4 well-abused Peavey Stadia speakers. The woofers are OK on at least 2 of them so I can make a pair, but all of the compression driver tweeters are dead. I would like to replace them but also prevent this from happening again by adding a fuse. What size and type fuse would be recommended?
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Re: Fuses for Peavey tweeters?

Postby ef37a » Sat Sep 12, 2020 11:39 am

A footy ground estimate would be to work out the current based on tweeter impedance and power rating.
E.g. for 8 Ohms and 50 watts 5 amps would be indicated. Not so and the protection afforded would be nil. A fuse needs several times its rating to blow reliably so you need a fraction of 5A. Unfortunately 'fusing' is not an exact science. Too high a rating, you get no protection. Too low and you get nuisance blowing. So, like loads for pistol rounds, you must work up to it.

For the 50/8 example above I would go for 1A slo blo (aka T) and give the speaker a good spanking with plenty of well distorted guitar and percussion. If no-blo go to 800mA. If they blow after 3 power chords, up them to 1.6A. You will find however that it is virtually impossible to find a fuse rating that will protect the tweeters and not blow at some point in certain circumstances, e.g. mains at ~250V and guitar feedback.

Holder mounting. If the speakers are only ever going to be used by you, fit a 20mm holder on the outside (jack plate?) However if you intend to hire them out or in anyway let Joe pub' use them, fit inline carriers INSIDE the cabs because JP will fit any old fuse or Kit Kat wrapper he/she can find.

It must be remembered that the main purpose of a fuse is to avert disaster e.g. a fire and not really the protection of 'delicate' electronics!

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Re: Fuses for Peavey tweeters?

Postby resistorman » Sat Sep 12, 2020 12:29 pm

We used to put 12v automobile bulbs in series with horns. Some speakers like the Yorkville Elite came that way. The bulb didn’t “blow” but acted as a limiter.
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Re: Fuses for Peavey tweeters?

Postby ef37a » Sat Sep 12, 2020 1:34 pm

resistorman wrote:We used to put 12v automobile bulbs in series with horns. Some speakers like the Yorkville Elite came that way. The bulb didn’t “blow” but acted as a limiter.

It is certainly one way, the filament will create distortion but probably not minded so much from a tweeter for PA?

I have to hand a 12V 21W lamp which has a 'cold' resistance of ~1 Ohm and would have a 'burning' resistance of 6.8 Ohms. What sort of rating did you have in mind Resistorman?

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Re: Fuses for Peavey tweeters?

Postby James Perrett » Sat Sep 12, 2020 2:04 pm

I think quite a few Peavey speakers came with bulbs for protection too.

A quick search shows that anything from 12V 6W interior lamp bulbs up to 24V 70W bulbs being used for this purpose.

Another alternative is the Polyswitch or Polyfuse which is a resettable fuse which uses a conductive polymer that goes high resistance at a certain temperature. Just make sure that you get one rated at 60V for high power speakers.
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Re: Fuses for Peavey tweeters?

Postby Folderol » Sat Sep 12, 2020 2:23 pm

An alternative is something like this. They have a nice characteristic in that they won't cut out with a very brief minor overload (so chose one for about half the expected current), but can break in less than a second for a major problem. They self reset after a short time. They also have a very stable characteristic, which doesn't tend to drift with age, unless they get lots of 'activity', and even then they fail safe, i.e. the cut out more easily.
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Re: Fuses for Peavey tweeters?

Postby Sam Spoons » Sat Sep 12, 2020 3:42 pm

Similar concept, I've used polyfuses to give some protection, with them the inevitable nuisance blowing only results ai a temporary loss of HF and when the overload is removed the tweeters com back on line of their own accord.
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Re: Fuses for Peavey tweeters?

Postby resistorman » Sun Sep 13, 2020 4:47 am

ef37a wrote:
resistorman wrote:We used to put 12v automobile bulbs in series with horns. Some speakers like the Yorkville Elite came that way. The bulb didn’t “blow” but acted as a limiter.

It is certainly one way, the filament will create distortion but probably not minded so much from a tweeter for PA?

I have to hand a 12V 21W lamp which has a 'cold' resistance of ~1 Ohm and would have a 'burning' resistance of 6.8 Ohms. What sort of rating did you have in mind Resistorman?

Dave.

It was trial and error. With the amplifier power and speaker components we were dealing with in the 80's through 2000 or so, I found that a generic incandescent American turn signal bulb worked well. I didn't much care about the details at the time... it was hard to even get specifications in pre-internet days. Besides, we were busy making music :)
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