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Old 20th June 2012, 10:51 PM   #1
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Default Speaker fuse protection

I have Wilmslows k100s with seas T25CF001 6 ohm tweeters in them. I initially put these tweeters in when a lead came out and I blew one of the original tweeters. Yesterday the missus did her weekely big house clean and last night when I switched my hifi on following a horrible scream from the tweeter the coil blew the coil. After further investigation it seems her duster had knocked a lead out . Calm happy thoughts.... Anyway apart living alone which is not an option, but did cross my mind a few seconds after for these tweeters what fuse would give me at least some protection? I thought initially of poly switches, but apparently they add a bit of resistance which is not ideal, so I thought of fuses. If I use a fuse what voltage and amps would work and is there any drawbacks?
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Chris
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Old 21st June 2012, 01:28 AM   #2
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It's a Polyswitch (PTC), it's resistance is so small you won't notice (or compensate), the problem is said it's that they might not be fast enough just like the "fast fuses" used by some manufactures. The difficulties is to calibrate such circuits without blowing to many driver tweeters testers
The alternative is the use of the lamp (crossover protection bulbs).
JBL control 28 speaker crossover protection bulbs - YouTube
The most professional way of doing this is with the use of a limiter like the Behringer. To note that some compression drivers (CD) have one (ptc) already from factory.
If you want to test a PTC in your system make use of a calculator.
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Last edited by Inductor; 21st June 2012 at 01:34 AM.
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Old 21st June 2012, 01:40 AM   #3
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Quote:
Originally Posted by Inductor View Post
It's a Polyswitch (PTC), it's resistance is so small you won't notice (or compensate), the problem is said it's that they might not be fast enough just like the "fast fuses" used by some manufactures. The difficulties is to calibrate such circuits without blowing to many driver tweeters testers
The alternative is in the use of the lamp (crossover protection bulbs).
JBL control 28 speaker crossover protection bulbs - YouTube
The most professional way of doing this is with the use of a limiter like the Behringer. To note that some compression drivers (CD) have one (ptc) already from factory.
If you want to test a PTC in your system make use of a calculator.
Strassacker: Speaker - kits - do it yourself
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Old 21st June 2012, 01:46 AM   #4
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Thanks inductor,
Is there any sonic drawbacks of using an inductor or a fast blow fuse?
Also any idea what size for Tweeter protection would be advisable?
My Tweeters are 90w rms and I am sure with normal listening I would never go anywere near that so I tought I could fuse them a lot further down so the fuse does not keep going with normal listening, but if a lead comes out again I dont loose another tweeter. The two times I have had a tweeter blow has been through loose leads causing a scream through the speaker.
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Chris
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Old 21st June 2012, 04:03 AM   #5
system7 is offline system7  United Kingdom
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The old KEF T27 used a 0.5A Time Delay fuse. Being a 8W rms tweeter. Being your SEAS is probably considerably more robust at 80W rms, I think you could try 1A time Delay. Or more. It is added add at the hot input to the tweeter crossover, usually a 20mm type.

But mate, this shouldn't be happening. Firstly it is good practise to always turn the volume control down before switching off. But secondly, do you have exotic speaker cable rendering the amplifier near unstable at high frequency? Or it could be the crossover design is not good on the tweeter and is presenting a very high impedance at high frequency. It is also possible your amplifier has an output Zobel network (8 ohms and 1uF say) added for stability, but that has fried. A good amp shouldn't go into oscillation on open circuit input.
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Old 21st June 2012, 06:07 AM   #6
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It is a Elliots sounds 180wpc mosfet power amp. Basically the lead to the preamp came loose causing massive buzz taking out the tweeter (that was the first time), this time I am not sure which lead was responsible, but when I pulled the amp out of the rack afterwards one of the 3 pin power leads fell out as did one of the rcas so I am betting on the rca being the problem. When you say the hot side I am guessing you mean the positive leg of the tweeter?
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Chris
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Old 21st June 2012, 07:35 AM   #7
system7 is offline system7  United Kingdom
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I didn't explain myself well there. The fuse goes on the input side of the filter to the tweeter.

When it blows it takes out the tweeter crossover, which protects the amp from any resonant effects from a filter with a blown tweeter. But hopefully it has protected the tweeter too.

When things go haywire, quite honestly anything can happen, but that fuse will add some protection to the amplifier too. Classic party syndrome when people drive the amp into clipping, for instance.

Top man, Rod Elliott, always like reading his stuff.
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Old 21st June 2012, 07:56 AM   #8
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Hmm not so easy.. The crossover in my speakers has the base unit and the tweeter on one board and the mid on the other so it is a bit hard without surgery to fuse on the input side. is the fuse a big problem on the output side or should I try to mod the crossover?
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Chris
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Old 21st June 2012, 08:03 AM   #9
system7 is offline system7  United Kingdom
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Look, I can only tell you what happens at parties.

People turn up the amplifier and it starts to clip. This blows the tweeter. Then the amplifier is driving an undamped filter. This is a horribly resonant load without the tweeter. So often as not, the amplifier transistors blow too.

There's no way round it, the fuse goes between the amp and the tweeter crossover.
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Old 12th May 2014, 09:37 PM   #10
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That's not what happens at my parties.

Too little power blows tweeters and midranges. If oyu have an amp that's not pushing a whole lot of wattage, as you turn up the volume the amp starts to clip. When that happens it heats up the tweeters really fast, and they fry.

I'm running a Phase Linear Series II Model 700. When the volume gets turned up too loud, the woofers reach their limits -- they start slapping against the voice coil and slapping against limits of full extension. This slapping can be mistaken for clipping. Well, the amp is trying to drive the woofer to move more than it is physically capable of moving, which heats the woofer up until it fries. Lots and lots of smoke.

Too little power kills tweeters. Too much power kills woofers. I roasted both 6.5" woofers in one of my Klipsch KG2.5s last week. I would suggest fusing the entire speaker. Fuse the speaker wire, even.

Charles.
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