Let’s face it. We all want to listen with the sound cranked. If you have the right dynamic processing, you can tune your system so that it sounds best when pushed, without your ears starting to bleed.
What is dynamic processing?
When we talk about “dynamics” in audio, we are referring to the amplitude (level/volume/loudness) of the audio signal. Dynamic processors change that amplitude in some way that should in theory enhance the audio.
The dynamic range of an audio signal is the difference between the highest level and lowest amplitude level. With high-resolution digital audio, we can have ENORMOUS digital range, but most commercially produced music is just really bloody loud. I’m not going to get into that now, but if you are interested, I will include some links at the end of the article.
Let’s look at the 2 most important dynamic processing tools.
Compressors are used to reduce the dynamic range, and most of the time this means the audio output is louder. They are used during recording, mixing, mastering, broadcast and streaming.
Compressors are not currently standard in car radios, but they are used in high-end systems, and there are aftermarket units that contain compressors.
Limiters limit the output (of course) by compressing the peaks at the highest part of the scale. That means that most of the audio content is not affected, but the loudest peaks are reduced to prevent distortion.
Gaining dynamic control in the car
The amplifier becomes saturated, as the input level gets too high. This produces distortion, reducing fidelity and clarity.
The loudspeakers begin to distort too, which sounds really harsh and nasty.
The loudspeakers are forced outside of their comfort zone by low frequency energy. Over-excursion leads to physical damage to the membrane.
It depends on your car, but it is highly likely that at high volume steps, the door panels will begin to resonate causing audible mechanical vibrations.
None of this is going to sound good. So what can you do to maintain control and a pleasant tonal balance at high volume steps?
Activate the limiters in your DSP
Play some music of a medium level (probably no rap), a few steps below maximum volume
Reduce the threshold of the limiter until you can hear it working
Reduce the output level until the distortion is gone or at least bearable.
Try this setting with some other music tracks. Does it sound good?
Now for the loud stuff…
Insert your earplugs
Try playing some loud commercial music a few steps below maximum.
Can you hear serious distortion?
Try to reduce the output or the threshold further until the distortion becomes acceptable.
If your taste in music is not LOUD, then tune the limiters to suit Classical, jazz, more dynamic music. If you only listen to the radio turned up loud, tune the limiters to suit that.
If you have inserted the limiter, but the distortion is still there, try experimenting by
Reducing the overall level of the bass with a filter
Try to increase the frequency of your high pass filter by 5-30Hz
Switch to a steeper high-pass filter slope (e.g. 12 or 24dB/octave)
It is ok to have some distortion at the maximum level for some loud tracks. This is acceptable, because you probably wouldn’t want to listen to 50 Cent that loud anyways.
Try listening to a well-recorded track that still has dynamic range. Many (kinda old) engineers like to use Dire Straits, Steely Dan or Jennifer Warnes. This kind of music should still sound good up to the maximum volume.
I will also write a detailed post about choosing the right listening material in the coming months, so watch out for that!
In most systems, the loudness function will be set and you won’t be able to adapt it, but I thought you should know what it does anyway as it makes a huge difference to your listening experience.
The loudness function is simply some filters at low and high frequencies which even out the tonal balance from low volume steps to high.
Why do we need them?
I mentioned earlier in the course, that our ears are more sensitive in the mid-range and less at the extremes of the frequency range. Take a look at these equal loudness curves (revised by the ISO in 2003). The graphs show that our ears are most sensitive in the range 2-5 kHz and least sensitive below 250Hz and above 8kHz.
At low volume steps, the loudness function boosts the low and high frequencies. With some car manufacturers, the loudness algorithm boosts as much as 15dB!
At medium listening volumes, the loudness algorithm should not affect the audio.
At high listening volumes, the loudness algorithm can be used to reduce the low and high frequencies. Reducing the bass will protect the loudspeakers and reduce distortion.
Reducing the high will be less fatiguing for the listener and hopefully you can avoid your ears bleeding all over your new leather seats.