All my tweeters blown (Sony SS-FCR6500) speaker package

[Thabto]

Hi Guys ... Need your help. I have the sony SS-FCR6500 speaker package(Front 180w, Center 150w, Rear 120w, all into 8 ohms), I am using with a Pioneer vsx-920 AVR (100w into 8ohm). Problem is all my tweeters are dead except one. The tweeters are connected parallel with a protection capacitor to the bigger drivers. What caused my tweeters to die, when they have a rating of 180w? What can I do to make sure it wont happen again? Can I modify the speakers somehow. Let me know.

[Mooly]

Tweeters usually have a low power rating of the order of a few watts only. You know the heating power of even 30 or 40 watts... a typical soldering iron for eg and so you can see that a small speaker coil can not dissipate anything like that amount of energy. Music contains little really high frequency energy which is why you see complete speakers rated at a few hundred watts. All the energy is in the bass.

One of the biggest causes of damage is clipping in the amplifier (running it to near its max output). When the amp clips, the tweeter sees what is then the equivalent of DC across it which is what burns it out.

[Charles Darwin]

If an amp clips the tweeter does not see the equivalent of DC.

Say I feed a transistor amp a 100Hz sine wave, no overtones or harmonics.
When we drive the amp into clipping it will put out a square wave which contains every sine wave which is a multiple of 100Hz at full rated power (or more).
No protection capacitor will or can stop the ones which are above its cut off frequency and the tweeter will just simply melt when faced with that. No DC present or needed.

This is easy to show with an analogue (ie subtractive) synthesizer.


To avoid that happening again avoid clipping by either being more cautious with the volume control or getting a substantially more powerful amp.
The rule of thumb in pro circles (studio or PA) is that the amp should be rated at at least twice the output of the speakers input capability, in your case that would be 360Wrms per channel for the fronts.
My tweeters are rated at 25W and I run them active with a 175W amp without ever having had problems.

[wintermute]

The other thing you can (and should if they are going to be abused) do is put appropriately rated poly switches on the tweeters. It Will save them from a clipping amp. I unfortunately blew many tweeters at uni parties before I discovered them, but after they were installed no more problems If someone turned the amp up too high the speakers just stopped playing until it was turned down again.

Tony.

[mizorizo]

Hello

When you are using a woofer connected parallel with a tweeter the back emf produced from the woofer will distroy the small power rating tweeter

I recommend using 4.7 Micro Farad capacitor AC capacitor or DC capacitor with a high voltage 250V in series with the capacitor

Why 250V ?

the capacitor can carry up to 10% of voltage rating reversed and this capacitor will be used as a high pass filter also will protect your tweeter

Ayman Ragab
Electrical Engineer
Cairo, Egypt

[seanny]

When you add a series cap you raise crossover frequency. He should turn down the volume or get a better tweeter.

[seanny]

Hi Thabto, from your description your tweeter has a first order crossover. You can protect the tweeter better if you install a 2nd order or higher crossover.

[Charles Darwin]

Won't do anything to protect a tweeter from a clipping amp.