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Tech Talk: Is it Getting Hot in Here? - cover

Tech Talk: Is it Getting Hot in Here?

June 21, 2016

If you’ve ever blown a sub, you know how it is… your car engulfed in the stench of hot metal mixed with a burnt air filter accompanied by thick white smoke that makes your freshly deceased sub look and smell like it’s sitting in a horror movie graveyard. Luckily, subs can be reanimated by the power of the DD Audio customer service and production teams! But in hopes of preventing us from performing a speaker autopsy just to discover another clipping incident, we’re gonna give you some info about why subs blow and how to avoid such!

Any way you slice it, clipping is the number one cause of death for audio equipment in any environment and odds are that you, the end user, are the one that caused it!

So what is clipping? Simply put, clipping is a type of waveform distortion that takes place when a waveform exceeds its output threshold therefore causing its peaks and troughs to be “clipped” off.

In a waveform the high points are peaks, or positive current, the low points are troughs, or negative current. These peaks and troughs correlate with the movement of a subwoofer. Normally, a clean waveform is always smooth and round but when amplified past its output threshold it becomes flat and briefly ceases to cycle. During the brief moment in which the waveform is flat the signal is actually being held at a constant amplitude above what an amplifier can reproduce thus the subwoofer is halted until the signal begins to cycle again.

Imagine you are pushing someone on a swing.  You’re going to stand all the way back at the furthest spot that the person swinging will reach, that way you can give them a good push.  A clean sine wave works the same way, everything runs smooth and it doesn’t have to perform any extra work in order to make the speaker return to center. Now take about two steps inward and try and stop the person mid swing for about a second, then start pushing them again, and keep repeating that process every time they swing back.  If you don’t get hit in the face when they swing back each time, odds are you’re going to get very tired from stopping, holding the person against gravity, and pushing them again. This is clipping.

When clipping is present the subwoofer moves less than normal due to the plateaus in the waveform and in turn causes excess heat to build up. Over time this excess heat causes the voice coil to break down and eventually fail. To prevent this from happening the gain sensitivity on your amplifier needs to be set properly.

Let’s say the volume on your head unit goes from 0 to 50 and starts to get noisy around 47. So, you back it down to 45 where it’s clean, measure the output, and discover the radio delivers a perfect 4 volts at this level! Next, you set the gain sensitivity on your amplifier to 4 volts and when you play your radio at volume level 45 your amplifier is safety outputting it’s maximum amount of power with it’s given circumstances! This means that you should never ever under any circumstance turn your head unit up past volume level 45! That’s the new maximum volume on your head unit! Period!

“Why not?!?”, asked the bass head.

Well, when you turn your head unit up past volume level 45 its output voltage becomes greater than what you initially set the amplifiers gain sensitivity to which in turn tells the amplifier to keep creating power beyond its maximum potential. Everything the amplifier is trying to create beyond its maximum potential is clipped signal and where there is clipped signal there is also a blown sub!