Why Are My Speakers Clipping?
We have all at one point or another experienced audio clipping, even if you aren't really sure what it may be. Let's take a look at what it is, how it is caused, and how best to fix it.
In simple terms, clipping is caused when the signal is too loud for either your amplifiers or your speakers. When an amplifier is pushed beyond its maximum working limit, it ends up going into overdrive. This overdriven signal makes the amplifier try to produce output voltages that are beyond its capability, which is what causes the clipped signal.
In some instances, this clipping caused by overdrive is desirable or even deliberate. Where would Jimi Hendrix have been, for example, without his Marshall Amplifiers and Roger Mayer effects, which created his signature overdriven guitar sound?
When watching a movie or listening to a piece of music, on the other hand, we want to listen to the sound as it was intended to be heard. Purple Haze has enough overdrive on the guitars without any more being added on your end.
Why is it called clipping?
We call this phenomenon clipping because that is what the waveform looks like. If you think back to your high school science classes, you may remember that a pure tone is represented by a sine wave, which is a smooth curve going up and down based on the frequency (pitch) and amplitude (volume) of the sound source.
If that sound wave gets too big, instead of having a nice smooth curve at the base and apex, we end up with a straight line connecting the uppermost and lowermost points of the curve. This flat plateau at the top or bottom of the wave will be an unnatural and jarring event that will sound horrible.
Three types of clipping
We have three types of clipping, which guitarists will be all too familiar with: overdrive, distortion and fuzz. Overdrive is often unnoticeable when it is at lower levels on the signal. Distortion happens when the audio begins to break up and quality is lost. Fuzz can often sound like a load of bees in a bottle. While we may want that sound when it is made on purpose on a guitar track, if the whole piece is affected, it will sound awful.
Why is my setup clipping?
One of the biggest causes of clipping in home hifi setups is due to mismatched impedance between the speakers and amplifier. The impedance is measured in ohms, indicating the amount of resistance offered by your speakers to electric current. The lower the impedance, the less resistance your speakers will offer, meaning that they will pull more power from the amplifier. If the amplifier and speakers are mismatched, too much power could be pulled, resulting in potential damage to your speakers or amp and distortion to the signal.
How can the damage happen?
If you have high-performing loudspeakers and a lower powered amplifier, your system will be prone to clipping. As your speakers don't get the power they need from the amplifier, they end up demanding more power than can be delivered. This can cause damage to the speakers. Especially at risk are the tweeters given the high-frequency harmonics often present in a clipped signal.
While clipping on its own is annoying, it is unlikely to cause damage to your speakers unless you are driving the speakers hard. You really need to push the volume to high levels in order to damage a speaker, and this is only going to happen if your amplifiers are misaligned.
How do I limit the possibility of clipping?
Quite simply, when shopping for amplifiers or loudspeakers, you should take note of the impedance of your existing gear and buy new kit that matches your system.
If you're starting from scratch, make sure your amplifier and speakers have the same impedance. This will help you to eliminate the likelihood of clipping, allowing you to hear whatever you would like to listen to the way it was intended, whether that is a wailing Hendrix guitar solo, a bell-clean piano concerto or sparkling movie effects.
For example, the phenomenal Bowes & Wilkins 702 Signature Floor Standing Speaker has been designed to produce full-range sounds in an incredibly clear and faithful manner to the original source. The specification for these speakers states that they have 8 ohm impedance and are recommended to be used with a power amplifier between 30W and 300W, into 8 ohms. Mismatching these speakers does not allow them to reach their full sonic potential.