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Moose1963

Speaker Wire with Inline Tweeter Protection Fuse

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I'm running a lot of power through my Klipsch 6000Fs and want to protect the tweeters from possibly blowing.  What type of inline fuse should I use on the speaker wire?  Thanks! 

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Assuming the tweeter is 8 ohms  nominal as the speaker itself is, I calculated a 4A fuse should be sufficient, if not a bit safe as I used the 125W continuous spec for my calculations vs. the 500W peak spec. Remove the binding post bridging straps, and run separate wires to the tweeter input terminals. A standard AGC tubular tubular fuse should be fine.

 

Someone please correct me if I'm wrong.

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Well, you always want to consider whether you are damaging your hearing by listening that loud !!!

 

My own view is that fuses are great for protecting woofers but not very good for protecting tweeters. Several techniques are possible. One is to use back-to-back diodes (this was done on the type AA crossovers). Another is to incorporate  an auto bulb protector. Search the threads by DJK for the schematic (it is a simple circuit).

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4 amps to a tweeter?

HA HA HA HA HA

Not fer long

HA HA HA

Sorry just struck me as a very funny as Fr. Guido Sarducci says.

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6 minutes ago, PrestonTom said:

Well, you always want to consider whether you are damaging your hearing by listening that loud !!!

 

My own view is that fuses are great for protecting woofers but not very good for protecting tweeters. Several techniques are possible. One is to use back-to-back diodes (this was done on the type AA crossovers). Another is to incorporate  an auto bulb protector. Search the threads by DJK for the schematic (it is a simple circuit).

Looks like a bulb and a parallel 10 w resistor

DHA2.jpg

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Posted (edited)

I recommend a polyswitch -

https://www.parts-express.com/electronic-parts/Fuses-Fuse-Holders/polyswitch-resettable-fuses

 

At around 60c , buy a few pairs in increasing amperage, put the lowest in circuit and try it, if it cuts out too often then move up to the next value.

 

Auto bulbs are going LED, which don't work as well due to much lower wattage.

 

Edit: Good description of how they work here -

https://www.jaycar.com.au/rxe075-ptc-fuses-speaker-protection/p/RN3460

Edited by Wirrunna
Added link to description

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11 hours ago, babadono said:

4 amps to a tweeter?

HA HA HA HA HA

Not fer long

HA HA HA

Sorry just struck me as a very funny as Fr. Guido Sarducci says.

Well, if it's wrong, offer a correction and show my math was incorrect.

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Many companies have used a lamp for tweeter protection, although most has been in PA systems. IIRC, Community had them located where they cound be seen through the grill so the sound many could see when they were being overdriven.

 

https://www.simplyspeakers.com/jbl-speaker-protection-bulb-sk3.html?gclid=CjwKCAjwjbCDBhAwEiwAiudBywc10gHPNWxRWoGBZiw5qzO1fsNgHp82VsKGB1otmt2RsoAOY0xTWxoCQWgQAvD_BwE

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4 hours ago, Peter P. said:

Well, if it's wrong, offer a correction and show my math was incorrect.

A 4 amp fuse would allow 128 watts to be delivered to a 8 ohm load.

P = I^2 x R. For a WHOLE speaker rated for 125 watts this is probably OK.

But just to the tweeter? If enough of the energy is of a high enough frequency that the crossover directs it to the tweeter you will have a blown tweeter.

Ask me how I know:)

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My calculations are correct then, because I used 8 ohms and 125 watts in crunching the numbers. Unless the speakers are bi-wired so the tweeter can be fused separately you have no choice but to fuse the entire speaker. Without knowing the max current draw on the tweeter, we're just guessing on how it should be fused. The owner's manual offers no information on which terminals connect to the tweeter!

 

The only other option is to remove the bridging straps and run the speaker cables to the tweeter binding posts directly. Connect a voltmeter in series and measure the max current, or use a peak hold feature on the voltmeter and take a voltage reading, then do the calculations.

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The T-35 (K-77) tweeter is rated at 5 watts long term and IMHO that can be assumed for other tweeters as a ballpark figure. 

Therefore long term current is about 0.8 amps.  Obviously the tweeter is the most delicate part of the system. 

 

WMcD

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10 hours ago, WMcD said:

The T-35 (K-77) tweeter is rated at 5 watts long term and IMHO that can be assumed for other tweeters as a ballpark figure. 

Therefore long term current is about 0.8 amps.  Obviously the tweeter is the most delicate part of the system. 

 

WMcD

Yes and I and many others with Klipsch speakers have proved it:)

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On 4/6/2021 at 6:39 AM, Marvel said:

Many companies have used a lamp for tweeter protection, although most has been in PA systems. IIRC, Community had them located where they cound be seen through the grill so the sound many could see when they were being overdriven.

 

https://www.simplyspeakers.com/jbl-speaker-protection-bulb-sk3.html?gclid=CjwKCAjwjbCDBhAwEiwAiudBywc10gHPNWxRWoGBZiw5qzO1fsNgHp82VsKGB1otmt2RsoAOY0xTWxoCQWgQAvD_BwE

How do you wire this in the circuit? 

 

Just add it to the positive of the tweeter? 

 

The DHA diagram above has a resistor parallel to the tweeter, is this for the circuit or part of the protection?

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I don't know.  Maybe it allows the lamp to light after you've blown out your tweeter.  !!!   I suppose there is some sense to this because some people might assume the tweeter is still good and continue to crank the power.

 

Though I'll admit it seems like the resister will not allow much current.

 

BTW, incandescent bulbs have a low resistance when not getting hot enough (current) to illuminate.  Then when there is sufficient current, i.e. temperature, to glow the resistance increases and thus supply some protection to the tweeter by current reduction.

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32 minutes ago, WMcD said:

I don't know.  Maybe it allows the lamp to light after you've blown out your tweeter.  !!!   I suppose there is some sense to this because some people might assume the tweeter is still good and continue to crank the power.

 

Though I'll admit it seems like the resister will not allow much current.

 

BTW, incandescent bulbs have a low resistance when not getting hot enough (current) to illuminate.  Then when there is sufficient current, i.e. temperature, to glow the resistance increases and thus supply some protection to the tweeter by current reduction.

Here is another schematic that I have without the tweeter protection

 

It looks like the 65 ohm resistor is for the protection circuit, maybe to maintain 8 ohms as parallel 65 and 8 ohms = 7.2, maybe add 0.8 ohms or so for the bulb and you are back at 8 ohms. 

 

 

DHA2-mod.jpg

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6 hours ago, tigerwoodKhorns said:

How do you wire this in the circuit?

In the OP's case, the speaker wire connects to the woofer terminal positive, and the fuse bulb replaces the bridging strap to the tweeter terminal positive. It's easy, and easy to access and observe to see if it's illuminating.

 

I'd put shrink tubing over the exposed wire, but leave the bulb visible.

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Ok..someone correct me if I'm full of it.......when power is applied at low levels the cold filament of the bulb acts as a low resistance allowing most of the power to go to the tweeter. As power is cranked up the filament starts to glow increasing its resistance, limiting the current and absorbing some of the power. That's why this works? or helps?

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1 hour ago, Peter P. said:

In the OP's case, the speaker wire connects to the woofer terminal positive, and the fuse bulb replaces the bridging strap to the tweeter terminal positive. It's easy, and easy to access and observe to see if it's illuminating.

 

I'd put shrink tubing over the exposed wire, but leave the bulb visible.

OK, so in other words, it goes in the positive to the tweeter.  The schematics that I posted seem to also require a 65 ohm parallel resistor. 

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7 minutes ago, babadono said:

Ok..someone correct me if I'm full of it.......when power is applied at low levels the cold filament of the bulb acts as a low resistance allowing most of the power to go to the tweeter. As power is cranked up the filament starts to glow increasing its resistance, limiting the current and absorbing some of the power. That's why this works? or helps?

In my view that is how it works, to the extent it works. 

I've never seen a Klipsch design with this technique BTW.

WMcD

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UREI used bulbs in some of their monitors, as has JBL, Radio Shack and others. They will work as a compressor, limiting the current to the tweeters.

 

If you want to dig enough (I don't), you can figure it out.

 

@JohnA  John can probably explain.

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