why do my tweeters keep blowing

[brsanko]

I've gone through about 4 Vifa D27TG-05s in the last year and I can't figure out why they keep blowing. I have them crossed over pretty high with solen caps and I don't typically crank the music way up but they've been blowing on me left and right. any thoughts would be appreciated.

[AGGEMAM]

Generally speaking it's because your amp is too small and starts clipping.

In general, too small amps blows tweeters, too big amps blows woofers (although the latter is rarely seen).

[brsanko]

100 w per channel I don't think it's too small.

[AGGEMAM]

Okay, I was generally speaking. It's a little hard too say without further information.

Such as:

What the exact circuit of the x-over is?

What other drivers are in your speaker?

What amp you have?

What source you use for the amp?

And so on ..

[zx3chris]

"too small an amp" is nonsense -- a speaker is rated for its thermal power handling -- how much heat it can dissipate when given the rated power -- The speaker does not care whether this is a beautiful perfect sine wave, music, or clipped square waves.

Generally speaking, most manufacturers will test speakers thermally using music as their source due to its low duty cycle, so they can print the higher number on the spec sheet. where as a pure sine/square wave is 100% duty cycle, music is generally not over 20%. Even if you distorted and played music clipped to hell, the duty cycle would not rise much becuase it would not sound good --

as far as why your tweeters are blowing -- ?? -- is the amp of your build? is there alot of dc bias on the output? im sure others have more insight

-chris

[brsanko]

well I'll tell you exactly what I have the exact crossover circut is the 3.3uf solen. I have two four inch 4ohm mid woofers I don't recall the brand name wired in series running full range and a side mounted 6.5" woofer of the same brand as the mids with a coil crossing it over at approximately 150hz. my amp is a cheap Technics integreated I picked up for $10 at a thrift store and my sources at the time of the blowing were my computer with a sound blaster audigy card and my MCS turntable with an ancient stranton cartridge.

[AGGEMAM]

Originally posted by zx3chris
"too small an amp" is nonsense -- a speaker is rated for its thermal power handling -- how much heat it can dissipate when given the rated power -- The speaker does not care whether this is a beautiful perfect sine wave, music, or clipped square waves.

Well sort of really. A clipping amp (presumming it's a class B type) will very often exibit a drift in dc zero. That's what is blowing the tweeter and not the actual power to the tweeter.

[AGGEMAM]

This might seem silly so bear with me but the cap is in series with the tweeter right? And coupled in parallel with the other drivers?

Your current filter is at 9 kHz if my calculations in my head are correct (it's very very late here) and there should be no way in hell your tweeter should blow with that kind of filtering especially considering the Vifa generally are considered very very durable.

If it's not the above then it has to be the amp that is the problem. Try to borrow one from a friend and see if happens again.

Or if you wanna save money, others here might offer you advice in ways to test if your amp is stable enough.

[brsanko]

you know I think I just may have realized what the problem is.
Some times I forget to turn the amp off when I plug the cable into the computer and it makes a very loud noise I've already blown two little two inch drivers out that I was using for my computer without crossovers I wonder if that is what was bowing my tweeters. and another thing does anyone know if these tweeter has any replaceable parts or if I would just have to buy new ones

[sreten]

)

"too small an amp" is nonsense --

It is true that for those who like music loud and don't mind it
being distorted low power amplifier clipping blows tweeters.
(Because the clipping increases average high frequency power)

3.3uF should be fine as a first order crossover.

Other reasons for blowing are ultrasonic amplifier instability and
dubious sources containing ultrasonic high frequency levels.

If the amplifier ouput devices do not look original then amplifier
instability should be considered. The turntable can be discounted.
Ultrasonics from your computer not so easily.

How do the tweeters go ? charred voice coils or broken wires.

Broken wires = use a second order (or more) crossover.
Charred = too much juice from somewhere.

sreten.