Ok I've never heard this before but then again I'm a car audio noob. I bought a set of audiobahn components...but wasn't ready to buy an amp for them. So i ran them off my alpine CDA-9807 which only puts out 50w x 4. The speakers were rated for something like 200w continuous. So anyways at about 50% volume level both tweets and one mid blew. I called one of the cartoys guy and he told me it's probably because it was underpowered. He says that underpowering speakers causes distortion and distortion is what blows speakers (i didn't hear any). Has anyone else ever heard this? Or am I just igonorant?

 

not positive but I believe that is true

also many people are fooled into thinking that a deck really puts out 50 x 4...

 

true...

Underpowering a speaker is almost as bad as pushing too much power to it.

 

The idea behind this is that when you are tempted to crank up your volume all the way, your amplifier will clip the top and bottom of the audio signal waves (called "clipping"). When this happens, the amplifier is sending your speakers damaging square waves.

 

clipping is the worst thing you can do to a speaker. the RMS of a clipped signal is something like 2 or 3 times the power the amp is designed to put out, because of the way the wave form gets mutilated.

 

You should have checked the minimum recommened power rating on your speaks first.

the 2 posts above are dead on.

This affects tweets the most. You crank your amp to hear the sound "at a reasonable" level, then there's a harsh transient (v. loud cymbal crash for example), but there's no reserve power left in the amp.... *poof*

I think this is worse than over powering your speaks. If you have too much power (no such thing, imo) you will simply turn the volume down when it starts to distort...
When you are under powering speakers you are constantly abusing them as the amp is near max the whole time, just to be audible.

 

thanks for the info guys.

 

I have heard the contrary. The maximum wattage that a clipping amp can put out is 2x its rms power. As long as this does not exceed the thermal power handling of the speaker it will not blow, assuming the speaker is driven in its normal operating (hz) range.

This was discussed in a long technical article.

 

but the clipped form become a square wave which causes more "usable power"... a large chunk more. I had to work on this problem way back in an engineer course i took but now I don't remember the exacts we worked out anymore

 

vteg is correct. A a speaker WILL NOT blow if underpowered. The only reason that underpowered speakers blow is because of thermal overload.

If you have a speaker like an L7 with 150 clipped watts running to it, it will never blow, because the voice coils are capable of supporting that thermal load. Now, say your sending it 2000 clipped watts, it's through.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">but the clipped form become a square wave which causes more "usable power"... a large chunk more. I had to work on this problem way back in an engineer course i took but now I don't remember the exacts we worked out anymore </TD></TR></TABLE> How do you figure it is a square wave? It will be a sinusodial output with flat spots on the top and bottom but not a square wave. Clipping is when the amplifier can no longer amplify the input. You essentially hit the power supply rails and can go no further than the rail voltage. This is to technical for here and most don't care to hear how it works. Essentialy though when you clip you are sending the speaker a dc voltage. The dc charcteristics of an inductor is a short. This can inrease the thermal demands on the speaker .




Modified by nsxxtreme at 1:40 PM 4/12/2003

 

what i meant was take more of a square wave form at the rms max

 

I challenge you to hook any 4 ohm speaker up to a 25v DC power source and see how long it lasts. Remember that an inductor acts as a short at DC.



[Modified by nsxxtreme, 10:37 PM 4/4/2003]

 

I don't think that is a fair test. The motor would not be able to cool itself under constant dc and thermal. During clipping, the top of the waveform is flat. The wave will still go the other way.

I hear that class D amps may put dc out and destroy subs. I have not really looked into this though. AB amps will have an ugly waveform when clipping, but a waveform that will allow the speaker to cool itself.

 

Correct but a clipped waveform will be at the peak voltage longer then intended. This would also depend on how badly you clipped the amplifier. Ocassional clipping doubtfully would cause much harm, clipping all the time may destroy the voice coil over time. As you mentioned this would depend on how well the speaker is able to disipate the heat. rjr162 has the general idea.

Why would you want to clip an amplifier anyway?



[Modified by nsxxtreme, 12:10 AM 4/5/2003]

 

I don't know. You may be able to get a slight edge in spl comps...

 

http://www.caraudioforum.com/vbb2/sh...hreadid=134964

He started the same debate over at CAF. 7 pages.

 

See what this guy rekons: http://www.canze.org.nz/bcae , lots of other info there too

 

do you know anyone that sends Direct Current to their speakers?


with DC, as you know, the cone will just move either up or down and just stay there. no cone movement, no cooling. but thats a different story...we're talking AC here

 

I was just trying to get my question answered...i had no idea it would turn into such a huge debate

 

lol... as I stated in another post, car audio is an inexact science. Unfortunately, everybody has an opinion.

 

A clipped signal is DC during the point of clipping so no we are not talking about AC. It was used only as an example, when you clip you are sending a DC signal to the speaker i.e the rail voltage. This is how I determined 25v for a 150w system. We can get into symantics if you like but most do not care to hear it.

I think what most are assuming here is that the amplifier is being overdriven to the point of clipping (I am). If you are not clipping the amplifier you will not blow the speaker.

http://www.jblpro.com/pub/technote/lowpower.pdf




[Modified by nsxxtreme, 11:26 AM 4/5/2003]

 

On termpro I found the answer to whether clipping increases spl. The answer is NO. I thought this should be the answer since a speaker that is not moving is not creating spl.

Clipping will increase harmonics in a sub which you will hear and think that you are playing louder. Of course sound from your sub is distortion. So this boils down to more power being introduced to the sub and no gain in spl. This is a lose-lose situation.

 

Haha.

Nice article nsxxtreme. I have seen some others like that also. I just realized normally when I think of clipping, I think of doing it to a sub which gets a lot of movment and is likely to live. That article deals more with clipping the high frequency drivers. It is hard to hear distortion in a sub. If you clip your high end speakers, you are a nut. I don't know who could enjoy listening to their music this way.

 

Same thing happens in a sub as a tweeter, the sub just has better thermal capabilites (usually). I metioned this once before. I though the article did a good job of expalining what was going on.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">Correct but a clipped waveform will be at the peak voltage longer then intended. This would also depend on how badly you clipped the amplifier. Ocassional clipping doubtfully would cause much harm, clipping all the time may destroy the voice coil over time. As you mentioned this would depend on how well the speaker is able to disipate the heat. rjr162 has the general idea.</TD></TR></TABLE>



Modified by nsxxtreme at 1:44 PM 4/12/2003