What is Clipping?

[wb131988]

On my Audiobahn amp there are 5 clipping LEDs. When I turn the volume up, 1 or 2 of them flash when the bass hits. What is clipping? Cheerz

[Google]

[sandness]

Essentially, clipping is overdriving an amplifier. Every amplifier has a number of transistors that are run off a given rail voltage. Since the output is basically limited to this voltage, attempting to drive it past leads to amp saturation. The output waveform is normally smooth and sinusoidal in nature. A clipped wave from an amp driven into saturation has flat peaks and the more saturated the amp, the more the wave resembles a square wave.

Here's a quick drawing made in paint:



The area under the curve is the power of the output. As you can see the power of a clipped signal has more area thus more power than that of the unclipped signal. All three waves shown are driven by the same amp with capable of driving Vmax. The dashed blue line shows that the amp gain is set too high and is trying to drive the amp to a higher voltage than it is capable of. Thus, it flat-lines when it reaches saturation: clipped.

However, the more it is clipped the worse it is for the speakers. The flat tops are essentially DC current being sent through the speaker's coil. This can lead to overheating and damage.

Some clipping is ok, especially in a subwoofer where the distortion it causes is typically hard to hear. So your amp seems to be ok where it is.

[2old2care]

Excellent Sandness....


Next lesson that few will understand:
Spatial Distortion as it pertains to automotive audio applications.
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[Josh]

well, he got that in before me..i wanted to look smart.

Funnily enough i learn that about 6 weeks ago
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[ToggleHead]

GREAT pic sandness.... i though i was gunna have to take over....but you got it ....=D
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[wb131988]

So basically, I need to turn down the gain on my amplifier to stop it from clipping?

[sandness]

A little bit of clipping can be fine as you have now. Try turning the gain down until the clipping is gone and see if the sound is any different. Most likely it will not. Thus, I'd leave it as is w/ minimal clipping.

[ToggleHead]

optimally....at absolute peak of sound...you want them to just slightly spike into clipping....so at the hardest hits.... those clip lights should just barely flash.... thats the best and most you should get from your speakers....=]
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[wb131988]

OK Thanks alot for the info.....

Also my amp has a subsonic filter and a phase switch (0 or 180 degrees). What should these be set at optimally?

[dene]

Sweet job sadness
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[wb131988]

I have recently been told that it is not wise to clip signal a sub AT ALL as it will fry the coils, so which is right??

[ToggleHead]

The AMPlifier should clip....not the subs.....sorry for not being more clear
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[sandness]

Any time you clip a signal, you are giving it more power than you would if you were to stop at the threshold of clipping. The only way it will fry the coils is if the sub cannot take the power- either thremally or mechanically.

A few things to consider:
[1] In a perfect world, if you have a 1000w RMS sub hooked up to a 1000w RMS amp, clipping the amp will thus exceed the RMS on the sub and result in death.

[2] Unfortunately, not all amps/subs are rated by the same standards. Thus a sub or amp can be either overrated or underrated in terms of its ability to produce/take power. Thus it is hard to speculate without experience with using the said product.

[3] As mentioned, RMS ratings on subs do not state the application in which they hold true. A 1000w sub will not withstand a full 1000w in all situations. For instance, if your enclosure is too big, mechanical power handling drops (more air in enclosure= weaker resistance to cone motion= cone travels to and fro more easily and can hit its mechanical limits) Likewise, the ability for a coil to handle the RMS power thermally is not standard across the board. So will that 1000w sub in the correct enclosure take 1000w of pure sine wave input for 10hrs straight? Or will it simply take 1000w of dynamic music input for 10hrs? It makes a difference.

Here's my view on your subs- you are still using the Type R's, right? If so, than from my experience, as well as what I have seen/read/heard, they will take more than the 300w they are rated at. I and many others, have run them with 500w for months with no problems. So whether you run them at 500w a piece unclipped or clipped, they should take it just fine. However, as earlier stated, the more clipping you get the more distorted it can sound. So you should be fine the way you are now.

[wb131988]

so the clipping indicators on my amp are telling me when the amp is clipping, and not the subs? I'm not sure why, but I think my Alpine HU goes up to a max of 35 vol, and I only have to turn it up to about 13 for it to start clipping. So to rectify this, I turned the gain down and bass boost then when I turn to volume back up, it does goes further without clipping, but the depth of bass that I had before just isnt there however much i turn the volume up. Any suggestions?

[wb131988]

Also, I wondered as my amp is one channel and the subs are wired up to 1 ohm, this should mean the amp outputs 800w RMS, so is this basically 400w RMS to each sub off the one channel? And what gauge speaker wire would you have recommended me use to wire the subs up in such a way?

Thanks for your efforts and time guys its a pleasure learnin from yaz

[wb131988]

Sorry about the three posts in a row guyz, I'm tired 2day.....

When you say its OK to let the amp clip, doesnt this still send DC current to the subs which actually damages them?

[sandness]

Here's my answer to your last 3 posts condensed.

[1] An amplifier clips, a subwoofer does not. The sub is a speaker which is a passive load. It plays whatever signal that is sent to it. If it was starting to clip with the HU volume on 13, then I'd say the gain was set too high. Most headunits will typically begin to clip at 3/4 volume. So you should set your gains such that they start to clip with the HU turned to 26 or 27. If the output is not nearly enough, it could be because the amp is not actually putting out what it is rated to put out, or you have simply become a basshead. If the latter, watch out. Upgrading can be severly addicting. In that case, a ported box will give you more output per watt. So if you are willing to build a new box with our help, that will be your cheapest upgrade with bang for the buck.

[2] Yes, your 800w mono means each sub is seeing 400w a piece. Typicall, 16ga is plenty for that power and shorter runs. 12ga is great, perhaps overkill, but you know, size does matter...

[3] As I said. some clipping is ok, especially since your subs can take more power than they are rated at. Will DC current automatically fry the coil? No. As stated originally, the extra power that a clipped wave produces compared to the unclipped wave (see picture in earlier post) can kill it if it cannot handle the total power. Speakers can play any waveform- sine, square, triangle, sawtooth, etc etc. But, since a square wave has twice the power of a sine wave at the same RMS voltage, it can kill a speaker who's RMS power handling is typically rated with a sine wave.

[wb131988]

You may be right about the basshead part, as I have chosen to sell my alpine 6x9s and pioneer coaxials, save up and get a set of Alpine comps and an Alpine amp lol Worthy choice?

As far as turning it up to 27/28, it is very loud (but not bassy enough) having been turned up to vol 18 when the gain's turned down! Helllllppppp

So now you know I'm a bass junkie, is there any way I can incorporate a port into my existing box successfully?

[sandness]

Going with the Alpine components and amp is definitely a good upgrade. They will perform much better than using deck power and the crossovers help make them perform better than coaxials.

As far as your amp gain situation, I question the sensitivity of the clipping LED's. I checked out your amp's manual from the Audiobahn site, and it doesn't talk about them at all. I'd probably shoot their tech support an email to find out how they should work in regards to clipping. I am thinking that as it is set now, it may be a bit too conservative.

As far as turning a sealed box into a ported one, it is doable. However, it is not always practical. Do you know the volume of your enclosure? If not, could you post the dimensions? We can see what options you have to port it.

[wb131988]

Yer I was dazzled when I checked my amp manual to find nothing at all about the clipping LEDs let alone the volt meter if i can remember correctly... Very strange indeed.

The dimensions for my box are: Length- 95, Width- 45, Height- 35 (at front, as box is not a cuboid, it slants down towards the back of it, this is how the subs point diagnally upwards..)

[ToggleHead]

cm's?
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[sandness]

I assume the box is shaped like this, from your discription:


If so, could you give us the figures listed on the pic?

[wb131988]

yup thats correct, i'll measure the dimensions tomorrow (Sunday) so keep an eye out! Cheerz

[fussnfeathers]

I should point out one thing, from a strictly amplifier standpoint.

Your clipping lights refer to the input, not the output. When you turn down the amp, you're not turning down the output (car amps don't have that option), you're turning down the input signal.....it's a gain control, not a volume control.

There's also a huge difference in amps. Solid state amps, in your case, will clip at a certain input level, due to the diodes used to create the output signal.......basically, they can put out so much, and then they hit a wall. Clipping your amp will NOT damage the speakers, but they'll SOUND like it did, because of the distortion. Again, in the case of solid state amps, the distortion isn't caused by the speaker, but rather the amp's circuitry clipping.......

I don't have a nifty diagram proggy, so let me try to explain the difference between solid state and tube amps..........a tube amp (think Marshall guitar amps) don't have a "clip limit" so to speak. They can overload, and still run. In fact, the best way to get the EVH "brown sound" is to use a variac to turn down the output of an amp, and overdrive the power tubes. Doing this will cause a heck of a lot more power to be drawn from the power source, and will eventually damage the amp, but it can be done.......if you look at Sandness' diagram, where the dotted lines are, a tube amp would have solid lines, meaning that they're putting out WAY more power, cleanly, than they should be.

Solid state is different. The MOSFETS can only handle so much, and when they hit that limit, they cut off sharply, which results in nasty, unwanted distortion. Don't worry that it'll blow your speakers, it won't, if they're rated for the amp's power. A solid state amp simply cannot put out more peak power than it's rated for, the MOSFETS don't work that way........which is why, using Marshall again, Valvestate amps sound like poop.

Another way to look at it...........if your amp is rated for 2000w PEAK (and this is the ONLY thing that rating is good for), it will never, ever put out more wattage than that, no matter how hot you run the input. The diodes simply aren't capable of it. Now, if the same amp had a tube output section, it could easily put out as much as double its rated peak, or 4000 watts.......which would blow everything sky high.

Anyway, long story short, no, clipping your amp hard won't kill your speakers due to power output, it's simply not possible with a solid state amp. They'll sure SOUND like you blew them, though.....but that's the amp making the distortion, not the speaker cones.
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[Xal]

^ Agreed.

The clipping is on your input and generaly when you are clipping on your input the sound is distorted. What I usualy do is put the volume of the headunit to the maximum I will use it at (eg 20) while playing a bassy song (prodigy breathe usualy) and then tweak the input gain up from 0 till it just peaks and then tweak it back till the peaking stops. That way you know that it won't distort at the volumes you will use it at. The output gains I follow pretty much the same pattern, tweak it up till I hear slight distortion from the sub then drop it back till its nice and clean. This will ensure you don't dammage your setup. Don't be a n00b and tweak it above its peaks because you will get crappy sound and thats not what a good system is for
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