Is it damaging to clip an amp? - Page 2

WOW crispy coils on ~600W playing program material.... I agree something doesnt sound right.


I wonder if the amp has anything to do with it? Do all amps behave the same when "clipping?" I think those amps have a variation of Bob Carver's power supply design at work. Its kinda like a smps i believe and doesnt behave proper when sent sine waves at full tilt, which is why they rate them 1/3 duty cycle and no RMS ratings.

Power is (voltage squared)/resistance.
0.707 squared is 0.5.

ah, roger roger.

How long did you play bass heavy music before the VC got fried?

they cooked about 20 seconds in. dl the song scary christmas and check it out lol
ive thrown the same song at my uxl with a channel on my fp14 clone and reference and it didnt even do anything. ahh well whatcha gonna do. lol

Possible troll on SI?

SI?

Stereo Integrity

Thank you, sir. Learning every day. That's the only reason I'm even checking out this thread. I have no clue what you guys are talking about but I hope I will learn something through osmosis.

Man, that's a bummer N8DOGG...

True for voltage or current: http://en.wikipedia.org/wiki/Root_mean_square -- may be thinking of the RMS value.

Power is the product of voltage and current: P = V * I = V^2 / R = I^2 * R

Power amps look like voltage sources (at least the vast majority do) so P = V^2 / R where R is the speaker's impedance is the usual way to calculate average power from RMS voltage.

Edit: Oops, sorry responding to the earlier post before realizing I was not on the last page, and that it had already been answered.

When I have blown speakers at less than mind-blowing volume it has been due to DC at the output, usually due to a bad device and/or failed DC servo loop. That has nothing to do with clipping, natch. However, clipping is often asymmetric, leading to an effective DC offset at clipping.

Run a 100Hz square wave though a 3mH inductor, see how the result looks across a 4 ohm load.

Sounds like the bass at 20 seconds in is around 60-80 Hz... thermal and not excursion limited I agree. I might have to buy that track to do some testing. I guess it was just too loud.

I agree, DC offset at the output of modern solid state amplifiers can be the bane of a loudspeaker alright. Anyone interested can google "DC Offset and You" which should give you hits to the AK site dealing with that item. Since speakers are reactive devices and inductive, they can withstand their rated power in applied AC signal voltage. But their DC resistance is relatively low and they can not take much sustained DC steady state voltage, and therefore a current that will quickly heat the voice coils and cause failure. Sometimes, even a bit of DC offset can damage speakers over time till one day you notice the speaker making static like rubbing noises because the voice coil has now swelled and warped causing it to rub the innards of the magnet structure.

Likewise, asymmetric clipping because of a failing transistor for one side of the outputs will do similar damage. "Flame Linears" sometimes had issues like this.

You can download it for free from Hedegaard's website. LINK.

Here is the first 60 seconds of that song. White arrow on 20 seconds. Though maybe he was 40 seconds in - since the first 20 seconds is an intro with bells.





Edited by baniels - 2/4/13 at 1:59pm

I went back and found the time the subs acted up on the song : 42 seconds is when it starts, she goes pretty deep, I under estimated when I said 20 second but there is no subs action for the first 10 second or so in the song.
I just hooked up my Dayton 18's I've got and ran it through the same song with the same amp and at the same volume I had the SI's at, there's a good chance if i didn't quickly turn it down, they may have also gotten damaged! they were starting to make some horrible mechanical noises hahaha but they are ok, no damage done. I shipped them out a hour or so ago in the SI boxes. I found a guy selling 2 more SI's so I bought them today and should have them next week. Sucks being in Canada but at least I can use my works account and get fairly cheap shipping. I think the subs were just pushed beyond their limits since the daytons pretty much did the same thing and they are pretty similar. Sims showed that would be the case at all but I guess we all know sims are not always 100% right. Ah well, no big deal, I can get them fixed easily enough.

You know it!!! hahahaha

Such a diehard IST fanboy.

Clipping = Distortion
Distortion = Bad
So just don't do it.

Most well-designed amps will self-protect if they get in trouble (heat, overload, DC offset etc); but that doesn't make it a good idea.
It will make stuff hotter and with less shelf-life than it needs to otherwise be.

That is true....... but I do have to admit, the SI's SQ was very good, better than I would have expected from the price point and IMO better than the daytons in the 3 CF boxes anyways. I got 4 only for the reason that I should at least try them out, man I feel like "The Ear" remember that guy with all the subs? though he makes me look like a n00b with his collection. I'm thinking of doing a paradigm sub 2 clone with sdx 10's after the G'horns are finished. That would be pretty sweet!

Of course I remember, Art! I wish he would come around more often. I even have a picture of his wall O subs as a picture that rotates on my Windows phone. I get to see it every day.

I'd like to collect sub drivers like him and make a wall like his.

Maybe I'm doing just that.... yeah, "maybe".

My Phase 700 was the least reliable amp I have ever owned. Sounded good when it worked, but... And it was indeed infamous for shorting output transistors that applied the rail across the speaker. Lost some good woofers that way...

I probably have at some point. For now, I'd be happy to simulate it. What inductor Q, and what edges (rise/fall times) on the squarewave? At 100 Hz, 3 mH is what, about 2 ohms impedance? What do you expect me to see, the impact of a 1o-LPF? It will still pass DC, so I am not sure the relevance to my post?

You're emulating a subwoofer driver voice coil. Well, not totally, as a voice coil also has capacitance, but close enough. Those who think that a square wave will toast a sub don't consider that no sub ever sees a square wave. As for the DC, if there's enough DC present to damage a driver that's got nothing to do with clipping the amp, it just means the amp is defective.

It's my understanding that when an amp clips badly enough it can produce well over the rated power? If the driver can thermally handle the extra power (as in the case of the UXL) it'll be fine. If it can't, you get crispy coils?

Or am I way off?

That's already been stated. One should read the entire thread before posting a reply.

I actually did read the entire thread, thank you. But I also see where people are saying that clipping can't damage a sub. So maybe lay off the snark and offer an answer to a legitimate question that was asked. Is this a semantic argument? If clipping can lead to significant power increases, which can then lead to overheating and burning up voice coils, doesn't that mean that clipping CAN damage a sub?

Ah, gotcha. I did state DC was not related to clipping, not sure I said explicitly it was a defective amp. I will state it now: DC on the output is due to a defective amp. My caveat is that assymmetric clipping can induce an offset, but if you are clipping that hard there are usually other considerations.

If the amp is connected directly to the woofer, say after an active crossover, then the woofer would "see" a square wave at clipping, I suppose. Depending on how good the amp. The VC itself will tend to reject HF signals, however, I assume that is what you are saying? For those still following this, at the second harmonic of the 100 Hz signal the 3 mH is already at 3.8 ohms and going up from there, doubling with every octave. As frequency rises the VC looks like a higher and higher impedance load (until the shunt capacitance kicks in, I am neglecting that) and thus dissipates less power. The HF energy is also falling (look up the frequency spectrum of a square wave) so it's also decreasing the power the woofer "sees" at clipping. Bottom line: unless you just flat out over power the woofer with an in-band signal, clipping won't damage it.

Aside: Was it EV or Hartley that used to plug their big 24" drivers into the wall at CES and let em' boom on the hour?

In any event I do not think we are in disagreement; perhaps in violent agreement? - Don

Hi Wth, I will attempt to condense down what is spread over multiple posts:

Yes, when the amp clips, it can produce well over its rated power. However, most of that energy is in the form of harmonics that are at higher frequencies. The crossover will route that energy to the mid-range and tweeter, so the woofer is not necessarily overdriven. But blowing up the tweeter is a distinct possibility.

This is one of many things I learned in this forum in the past few weeks. Thanks, everybody.

Thanks for that. But in dealing with just the sub-stage, is the contention then that you can't damage the VCs with excessive clipping? Because if it's the harmonics and they are only at play in the tweeter/midrange/woofer area then it wouldn't apply to subs at all. I find that hard to believe. And how does that square with what Nick from Stereo Integrity said on the matter?