Axiom Home Page Forums General Discussion Technical Questions Clipping

I'm new to this so please don't LOL. I didn't know I had a crappy system till I started researching for new speakers. What exactly does clipping sound like? Is it similar to the sound of a kazoo? And if not, what could be causing that; A cracked woofer? Also, do blown speakers still work or do they just sound bad? One more question. Why do home theater receivers have two options for attaching speakers and is one option better than the other? Thank you for curing my ignorance in advance.

I can't help you on the cliping, never heard it before. As far as your receiver having options for connecting speakers, there are actually three, bare wire, spades or banana clips. The latter two are just a personal choice for convenience, no difference in sound quality, the banana's are just easier to connect in tight spots.

A KAZOO?.............(LOL).


Sorry.

Unless I'm badly mistaken, clipping is what you get when you try to get too much volume from not enough power. In other words, the amplifier can't keep up with the demand for power, and the louder parts of the signal get flattened out (picture a sine wave that's flat on the top and bottom...) because there's no more juice. This is really bad for speakers, besides sounding distorted. Speakers driven too hard with a weak amp tend to get burned out faster than when driven to the same level with a powerful amp because of this signal distortion.

Damaged speakers also sound bad, (Understatement!!) but I'm not sure how to describe the sound. Maybe like paper fluttering in the wind?

You may be onto something with clipping sounding like a Kazoo.

The problem with clipping is that it tends to blow your tweeters.

I have had "blown" speakers in a car system and they would still work. They just sounded bad.

If you can look inside your speakers, see what sort of drivers are in them. Maybe you can listen to each individual driver and see how it sounds.

There are actually two "sounds" of clipping... hard (digital) clipping and soft (analog) clipping... both are types of distortion.

In the digital world, there is an absolute hard maximum after which a signal gets clipped, it's at 0dBFS, if you're familiar with computers, every CD sample at 1/44,100th of a second can be an amplitude (loudness) of between 0 (00000000 00000000 - digital "black") and 65,535 (11111111 11111111 - the highest value a 16 bit sample can hold) what happens if the engineer screws up and makes everything on the disc too loud? Say it's twice full scale, that means a sample at 50% of the full amplitude is recorded as 65,535... now what's written to the disc when a sample is at 75% of full amplitude? The same value, 65,535... there is nowhere higher to go, the waveform can't be correctly approximated and distortion results. What does that sound like? This clip should help. This first half of the clip is very much clipped (then attenuated to match levels), the second is as the album cut sounds.

Now, soft clipping, in the analog world (like your receiver) is similar, but it's "softer"... there is more "headroom" in an analog signal. As the signal reaches full saturation, it starts sounding more compressed - which is an odd term for most to come to grips with - compressed sound actually sounds "bigger"... new pop/rock music uses a lot of compression, it makes the quiet parts louder and the loud parts quieter, it kind of removes the dynamics, so guitar fret noise, breath sounds, etc sound louder in relation to the music. Why do they do it? It's that Wall of Sound... gotta be big, and loud. Anyway, so as your receiver approaches clipping, it will "roll off" those high bits of amplitude, which actually doesn't sound as bad as digital clipping. I tried to look for a CD without compression already added at the mixing stage so I could show an example, but I couldn't find one in my collection here. I'll have to look through Lisa's collection for something classical.

So as your receiver approaches clipping, it compresses the waveform, and shortly after that it starts behaving like digital clipping, by distorting the sound.

Is clipping bad? Not necessarily for everyone, the entire "tube sound" that guitar players strive for is the sound of the tubes being pushed into clipping... a tube overdrive is the same idea, only taken a bit further... then if you take that even further you get the fuzzbox sound.

Clipping - great for guitars, bad for home or mobile audio.

Hope that helps, more info than asked for, but... felt like giving a discertation.

Bren R.

...because there's no more juice...

____________________

So, if there is no more juice than why is there a concern of blowing the speaker?

The fear of blowing a speaker with a weak amplifier is often overblown . If you have a 300 W or 400 W rated speaker what harm can be done from a 50W amplifier? A 50W amplifier can not put out more than 50W, period. The speaker woun't even break a sweat.

A real danger comes from 'matching' amplifier and speaker. For instance, if you have a 200W rated speaker and 200W amplifier than you have to watch for clipping. Clipping distorts the waveform and add tons of higher harmonics. That's why clipping sounds raspy. These harmonics are re-directed by the crossover circuits to the tweeters and there is enough juice to burn them.

Gena: just because you have a speaker rated for 100 watts does not necessarily mean that all the drivers in the speaker are rated for 100 watts. Somewhere I recently saw an article/ post on this. It could have been on this board. Bottom line, because of the actual musical power spectrum, the tweeters are rated quite a bit less than the actual speaker rating by most manufacturers. Wish I could remember how much.

First, I didn't say 100W speaker, I said 400W speaker and 50W amp. Second, if the tweeter is weak, it is usually blown just by increasing the total volume level and the corresponding increase in the high frequency component. Doesn't have to do anything with clipping. Sure, clipping will give some extra power due to distortion, but the tweeter will be blown by the high level non-distorted part just due to the high volume.

Gena I hate to tell you but you are wrong here. You are far more likely to blow the tweeters out of a speaker that can handle 400 watts with a 50 watt amp than a 200 to 300 watt amp. Clipping can fry tweeters fairly quick.

From Ian

"The key is in amp clipping. Very small amplifiers driven into clipping can damage very high-powered speakers. It is like sending little dead shorts to the voice coils, which cause them to heat up and melt down. If the power is clean the M60s will take ridiculous sized amplifiers with no problem. In our power testing we use Bryston 7Bs, which are putting out close to 700 watts. The test involves both modified pink noise continuous for 100 hours at 250 watts followed by another 100 hours of heavy rock and roll. This is way above the standard rating methods of 5 to 8 hours of modified pink noise at the rated power."

Ian Colquhoun
President & Chief Engineer