What actually happens when speakers CLIP from bad power?

[gibby214]

Does the wire in the magnets fry off it's insulation? or what

Does damage happen in the first seconds or minutes or hours.

Like those 20 seconds it takes you to get to the old Kenwood reciever because the 2yr old cranked the volume on it.

Just a thought I had while considering some used speakers. How do you know they are good.

Just because the cones are not dented means they are ok.

If the same speaker was pushed with clean power but insane amounts. Would the cones of the woofers or tweeters tear or pull the surrounds out. But the hidden parts be intact.

[DrWho]

when an amp clips, it essentially sends DC through the speaker (instead of AC). This is bad because it quickly heats up the voice coil and usually results in thermal breakdown (it melts). It is the nature of a voice coil to become completely damaged all at once...in other words, if it's working now then it's never really experienced any damaging power in the past.

You know a speaker is good when it sounds good...any kind of damage results in very audible artifacts.

[PrestonTom]

With a 2 year old in the house, you should consider putting a fuse on the speaker line.

No, won't degrade the sound, but it will save your speaker.

Good luck,

-Tom

[Duke Spinner]

i Fuse any Speaker ...cheap insurance ...

use a fast Blow Instrument fuse

[sfogg]

When an amp clips it is literally 'clipping' off the top of the AC waveform it is trying to produce. So instead of producing nice sine waves it is producing more of a square wave shaped signal. A square wave is nothing more then a sine wave with many many harmonics of it. Clipping an amp tends to kill tweeters first because all those harmonics increases the total amount of power sent to them and they can quickly get to the point of overheating and melting the voice coil.

If by speaker 'clipping' you mean simply overpowering them (even with clean power) it can result in a few things. Too much heat build up can damage voice coils and if drivers are badly overdriven then can be physically damaged from passing xmax.

Shawn

[heresy2guy]

"Clipping an amp tends to kill tweeters first because all those harmonics increases the total amount of power sent to them and they can quickly get to the point of overheating and melting the voice coil." - sfogg

__________________________

True. When you hear of people "blowing" their tweeters it's almost always due to them overdriving (and thus "clipping") their amplifier. Better amps tend to have higher amounts of dynamic headroom (reserves) to help prevent this.

Then again, if you don't turn your volume up past the half-way mark and/or manage to keep your bass/treble settings closer to if not exactly "flat" at high volume levels you should be fine.

Getting more power then you need suffices too (i.e. getting a 200 wpc amp if you only intend on using 50 continuous watts, which allows you to have approximately 4 times the continuous power available for reserves, or musical "peaks"). This should afford you plenty of dynamic headroom (about 6db) to ensure that your amp doesn't clip and damage your tweeters. Of course, if your speakers can only take 50 continuous watts and you pump the full 200 watts into them (continuously, as opposed to peaks) then you're probably going to open up all your voice coils anyway, reagardless of whether or not the amp clips.

Still, in my opinion, it's better to have more power then you need (so the amp runs "clean") then to not have enough and stress the amp (so the amp clips).

Since Klipsch speakers are so efficient (my La Scalas are 104db with 1 watt at 1 meter) that it seldom takes more then 1 to 10 continuous watts to produce very to extremely loud levels in a typical living room. With this being the case, technically speaking, a 50 wpc amp should be enough to afford a La Scala plenty of dynamic headroom (in the form of the unused power providing for a reserve of 4 times or more the continuous power being used) to prevent the amp from clipping.

If the amp itself has a low dynamic headroom rating (1 to 2 db) and you use the full 50 continuous watts available, then there won't be much left over for the peaks (or transients) and then the amp will surely clip and your speakers will be at risk.

So, you can basically get more power then you need (as long as you don't use it all continuously) or you can look for an amp with extremely high dynamic headroom (6 to 7 db), which should allow you 4 or 5 times the full-rated continuous output in reserves. Either way, the goal is the same: make sure you have enough in reserves so you don't overdrive ("clip") the amp and damage your speakers.

-H2G

[gibby214]

Thanks guys

What is the easiest way to fuse?

Can you "in line" a blade fuse on the + speaker wire.

Do both the HF and LF. What amp ratings of those instrument fuses would you use? I have RB75's bi wired HF and LF. And RC35 and RB25 for rear and surround not bi-wired.

[gibby214]

With a 2 year old in the house, you should consider putting a fuse on the speaker line.

Actually I have twin 2 year olds in the house and a 5 yr old

[gibby214]

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On 8/12/2005 2:20:39 AM DrWho wrote:

when an amp clips, it essentially sends DC through the speaker (instead of AC). This is bad because it quickly heats up the voice coil and usually results in thermal breakdown (it melts). It is the nature of a voice coil to become completely damaged all at once...in other words, if it's working now then it's never really experienced any damaging power in the past.

You know a speaker is good when it sounds good...any kind of damage results in very audible artifacts.

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So good sounding ebay or pawn shop speakers could have lots of life left in them. They really are not half used or burnt out. Correct?

[heresy2guy]

The only way to verify that they're okay is to listen to them yourself. Otherwise, you're simply trusting what someone else tells you. Some people are trustworthy (your friends for isntance) and some aren't (scammers, rip-off artists). If somebody from this board auditioned a pair of Klipsch for me and told me they sound fine I'd trust their judgment.

[crazytubepower]

The only thing with used speakers is sound and driver state, if they sound good and the drivers look good, they are most likly good!

[Spkrdctr]

If a speaker is playing fine, then it is ok. I did destructive testing on the Bose line of speakers, so I was able to fry them slowly, and study the degradation of the voice coil in different nightmare scenarios.

[WMcD]

We all here on the forum have had a few go arounds on this.

I agree driving an amp to clipping is bad and will fry speeakers.

OTOH I believe the Fourier analysis of the square wave really does not tell the story. If you look at the math, the newly created frequencies are indeed generated. But they are at relative low levels. I'll agree it is something to worry about. But not the whole story.

Rather, I believe that when you are driving a given amp to clipping by some frequency which would flat top, you're also driving up the rest of the program freqencies to the max and also doing it long term.

For example, the Hertiage mid is probably good for 40 watts long term and the tweeter is good for 5 watts. Lets give the woofer a 100 watt rating.

If you turn up the volume on some music on a 100 watt amp, you may not know exactly the freq which is going into clipping. Pop and rock puts power peak in the bass and classical puts it in the mid.

But for the most part, if you drive a 100 watt to clipping in one frequency range (say the bass), the other ranges are not far behind, and they may be exceeding the long term limits of the drivers.

Also, unless there are very rapid roll off in the crossovers, high power to an adjacent driver is going to get through the crossover.

Consider that PWK increased the crossover roll off rate for the tweeter, and granted the Zeners (the latter fact argues against what I'm saying). If it was a matter of just Fourier harmonics into the tweeter range, they'd still get through even a brick wall filter. So steep filters help but not the Fourier frequencies.

Rather, I think what happens is that full power midrange freqs up to 100 watts get into the tweeter, particularly if there is only a 6 dB per octave filter.

The same might be said of bass getting ito the mid.

My major point is that you don't need Fourier harmonics to explain fried mids and tweeters. You only need a 100 watt amp being driven to near limits. It is simply a matter of too much power.

- - -

The failure of bass units is a bit hardered to explain. I lost an EVM-15L in a home made K-Horn to a Telarc disk (the one with a warning) playing sub sonics through a 20 watt ss amp. Maybe the amp went nuts at being clipped at 20 Hz and put out d.c.. Or maybe the signal just coincided with the resonant freq of the bass driver, and tore it apart. In my experience, you don't hear the subsonics, only a crackling noise.

BTW it can be an expensive experiment. However, if you have a signal generator, it is not difficult to find the frequency where a woofer bottoms out at resonance. It makes a clanking noise you would think the woofer is not capable of making at all.

I'll guess at some numbers here. The woofer may be rated at 100 watts. Yet 10 watts at resonance can cause bottoming out. Do it too long and you mechanically distroy the woofer. Music can do the same, I'd think.

- - - -

So lets look at the situation and do a wrap up. We're thrashing the amp to the edge of its performance limits. We're thrashing the speaker components to the the edge of their performance limits. Something breaks. Maybe not the first time, but people test the limits. They may do it with efficent speakers because they sound clean at high levels.

Unless you have very controlled testing, it is inaccurate to imagine that is always one thing, like clipping, which caused a failure. Rather, when you run everything into the red, there are going to be a lot of problems. So don't do it. Smile.

Best,

Gil

[Jay481985]

pardon me from butting in but is there any website or diagram to put a fuse in the speaker cable?

[PrestonTom]

Re: Fuse on the speaker

It really is simple.

Radio shack has in-line fuses. Get the 20mm kind and solder it on to one side of your speaker cable. The fuse need not be large, for the impedance and efficiency of a klipsch heritage model, the size would be between about 1 to 2 amp. Be sure to use fast acting fuses (not SLO-BLO).

It is good protection.

Good Luck,

-Tom

[Spkrdctr]

I'll reply later when I get some time tonight. I'm signing on buying a house and have to run. I can answer all of the questions since this is my area of expertise. I usually answer with small quick posts, I'll go into more detail tonight. For once, and just this one time, I really am the expert!

Now if I can only convince my wife that I really do know something........

[Spkrdctr]

Ok, I will keep this very simple so people with no real technical experience will hopefully understand it. If I botch the job of explaining it, please ask me questions.

When a reciever or amp clips, it produces a square wave. Pretty much everything about the square wave is unimportant, except that it is square. When the signal is "riding the rails" (the peak voltage ability of the amp, causing the square on the square wave) it is clipping. The signal is stationary in amplitude, with a stable voltage output with no varying wave, it is now DC that is being put to your speakers. The really cool part about this, and my comments many times on reciever power, regarding current, is that once the amp is putting DC to your speakers, even if only small amounts, your power supply sees a near short, much less than 1 ohm, so your power supply (even cheap tiny ones)are capable of putting out massive current (yup, even the cheap Pioneer recievers etc) to the speakers. The DC stops the voice coil and holds it in one spot, therefor causing the impedance to drop to a short. So the inrush of current melts the coating on the voice coil wire first, and then melts the wire itself until you get an "open" coil which passes no current at all, the speaker is now dead.

The speed of voice coil death is dependant upon the amount of clipping. Medium clipping will take some time and you might, if your very lucky, smell something burning and turn it down. That smell is the coating on the voice coil wire melting. If you clip hard, such as having the reciever turned up all the way, it might take less than 30 seconds to toast a small tweeter coil. Many times all of the drivers will get some DC to them from clipping. But, clipping is frequency dependant too. If you have a deep bass CD of rap music, the main driver will go and your tweeter may be just fine. It all depends on the clipping, music and speakers.

Now, do I dare bring up Bose? The Bose drivers are pretty tough. They can take a massive beating and keep going so they have minimal warranty claims. They just don't sound all that good to me, due to design, materials and cabinet geometry I guess. Make no mistake about it, those cubes will take a major thrashing before they go. Now if they just sounded better.....

So, in talking about clipping and speaker driver destruction, you never want to push a low powered reciever or amp hard. They will all take out the most robust voice coil.

This is also why it is so imp[ortant to NOT EVER DRIVE YOUR SYSTEM INTO CLIPPING, EVER! You can't see inside the drivers to monitor the voice coil damage. And for Goodness sakes, you never want to fry high quality Klipsch drivers just for fun. It can get expensive.

"High current" as used by the industry has almost nothing to do with clipping. It is the amount of voltage you have for your power supply rails that is important. This is not adjustable. You must buy a very good unit like the Sunfire reciever (and a few others), or just about any stand alone high quality amp to get the higher voltage that you need. High current has its place, but for clipping, it is voltage that runs the show.

Also, ALL of the amps and Sunfire recievers, etc. that I know of, that have high voltage, are also high current. So, when you buy very high quality, you get the whole package as a well designed unit. The Engineers want you to have it all. Their reputation stands on their product.

I hope I made this understandable and I also hope it is helpful.

Don't even let me start on the Bose Bass Module.... talk about junk!

[MrMcGoo]

Spkrdctr,

Your explanation of clipping is one of the best that I have read. Thanks for the information.

Bill

[gibby214]

Thanks spkrdctr.

Just was thinking back 10 years ago in college. My reciever was down so my roommate hooked up his detachable boom box to my speakers for a whole weekend of partying. I'm thinking there was a lot of square waves riding the rails, "If those things even have rails" uugh

[psg]

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On 8/15/2005 9:40:24 PM MrMcGoo wrote:

Spkrdctr,

Your explanation of clipping is one of the best that I have read. Thanks for the information.

Bill

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I'm not sure I agree with that explanation. I always understood clipping in terms of a square wave, representing a lot of harmonic content (think Fourier series if mathematically inclined). A clipped wave is not DC for a very long time as it alternates between +DC and -DC (e.g. a square wave). The explanation also doesn't side with tweeters blowing as it hints to the woofer coil burning out.