Car Audio DSP - How To Get the Perfect Sound in Your BMW

Paul Smith
Mar 10, 2020

Everybody wants their car stereo to blow people away with powerful, well-balanced, clear sound. For most people,  picking up a new set of speakers or an improved amp is the first step towards making that dream come true.

Great hardware isn't enough, though. It doesn't matter how good a speaker is if you're feeding it a lackluster signal.

So here's a pro tip: the best way to awesome sound is with a quality DSP amplifier or DSP processor. Car audio enthusiasts usually advise starting off with that kind of solid foundation, which is just one  reason to get a BMW amplifier replacement.

If you aren't sure what DSP technology can do for your car stereo, we've got answers to all your questions, starting with the DSP processor fundamentals.

What is DSP?

A digital signal processor (DSP) is exactly what the name suggests: signal processing done digitally. This usually means using special DSP software or a DSP processor chip.

Take audio, for example. Common audio formats like MP3, AAC or FLAC encode your music digitally, so without a digital music player, you won't be able to listen to it. Many do more than just play music, though, and also let you use a digital EQ to make changes to how your music will sound.

Whether a simple three-band EQ or a full graphic equalizer, the idea is the same: the digital signal passes through a chip which computationally processes it. With an EQ, that means analyzing different frequencies and boosting or reducing them. The signal output (the music played by the speakers) is different from the signal input (the music saved in the file). That, in its essence, is digital signal processing.

An equalizer isn't the only form of DSP, and many other effects are possible. Some music players offer compression, for punchier, more present sound. High-end home stereos include intelligent room correction, to make music sound better in poor acoustic environments.

Digital signal processing can also be used to modify non-audio signals, like video, but when it comes to car audio, DSP refers specifically to sound manipulation.

Why do we need a DSP processor?

So signal processing lets you adjust your sound, but why would you want to? Isn't it enough to listen to the music how it was originally intended? In short, it depends.

If you're listening to music in a studio environment, using professional monitors or high-end headphones, you're going to hear what the producer was aiming for. The further you move from that ideal, though, the further the music is going to deviate from how it was 'supposed' to sound.

BMW DSP amplifier

Let's take EQ again. If your speakers have poor bass response — as many smaller speakers do — you might need to use an EQ to boost the lower frequencies. This will give a sound that is closer to the original; the louder bass from the EQ and the quieter bass from the speakers cancel each other out. Of course there are limits to what EQ can do; small speakers are never going to be able to produce visceral bass — the laws of physics still apply.

Listening to music in a small space, you might have the opposite problem. Base frequencies have longer wavelengths than higher frequencies, so are generally affected more by small spaces with shorter distances to the walls. The sound of low frequencies reflecting off nearby surfaces can cause unpleasant bass resonance, overwhelming the rest of the sound. In that case, using an EQ to reduce the offending frequencies will make the overall sound more balanced.

Other forms of signal processing are also often used to account for the quirks of your sound system:

  • Dynamic compression levels out the volume of your music, making quiet parts louder. That makes it a popular choice for people using headphones in noisy environments.
  • Time alignment is used in multi-speaker setups to keep the music from all speakers sounding cohesive, by delaying playback from individual speakers based on their relative distance to the listener.
  • Adjustable crossover lets us control exactly which frequencies are sent to each speaker (subwoofer, mid-range and tweeter), to make sure each plays only what it's best suited to. This generally means richer, more accurate sound.

As car stereo systems need to perform in challenging circumstances — small spaces without proper acoustic isolation, speakers constrained by your vehicle's interior,  underseat woofers that might sound muffled — quality signal processing is vital to get your music sounding its best. A good car audio DSP amplifier will let you shape your sound to fit your vehicle and preferences.

Analog vs digital signal processing

There's more to signal processing than DSP. Analog signal processing (sometimes known as ASP) was more common in the past, but analog hardware has now been almost entirely replaced by digital alternatives. The difference between DSP and ASP mirrors the general difference between digital and analog audio. In a nutshell, an audio DSP treats the signal as digital data to be decoded, whereas an ASP does its work on continuous frequencies and electrical currents.

What does that mean in the real world?

Analog signal processors are usually based around an electrical circuit. As the audio signal — in the form of electricity — passes through the circuit, components like transformers and resistors modify the current. In changing the current, the ASP also changes the sound.

DSP, on the other hand, makes use of a computer, microprocessor or dedicated digital signal processing chip, generally running special DSP software. This software analyzes the audio signal — in the form of digitized data — and makes programmatic changes. The result is very precise audio control. As DSP tools are limited only by the software they're running, they also tend to offer far greater flexibility than their analog counterparts.

For some, DSP lacks the warm, 'realistic' sound of analog — the digital vs. analog debate among audiophiles stretches to signal processing tools, too. Analog signal processors can also have the edge in some high-frequency applications; real-time DSPs need to crunch a lot of data to keep up with the music, and like with any computer, a slow processor can be a bottleneck. These strengths mean analog hardware still sees some use — in the home stereo scene, at least.

What is the best car audio sound processor?

In a car audio setting, though, analog loses its advantage, so it's no surprise that DSP is now the only serious option.

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Most music you listen to in your car is already going to be digital, whether it's an MP3 file stored locally, online streaming music or digital radio. A vintage analog signal processor isn't going to be able to live up to its promise of beautiful, analog sound with that source material. And as most digital music is encoded at a relatively low bit-rate, even a modest DSP won't have any problem processing the music in real-time.

DSP car amplifiers have replaced the analog alternatives of the past by offering a robust package packed with options. That flexibility is particularly valuable in challenging situations, like keeping your music sounding great in your car. Precise control over the sound gives you the power to adapt to your car's interior. That's why we chose to use a powerful 64-bit DSP for our  Premium Audio System amplifier for BMWs.

How to program a car audio processor

A programmable car sound processor also makes it easy to try out new things. With the right programming tools for DSP processors, it can be as simple as connecting your laptop and loading a tuning file.

At BimmerTech, our Premium Audio System DSP amplifier comes with accompanying DSP tuning software for your PC. Our sound engineers prepare DSP tuning files for every BMW model and  all supported BMW sound systems, from HiFi (S676A) to Harman Kardon (S674A), as well as for our own Alpha One BMW replacement speakers. Download the one for your vehicle and you're good to go!

This takes the hassle out of programming your car audio processor, and also makes sure you're tuning safely. Many aftermarket car audio amplifiers — including BimmerTech's — are capable of outputting more power than the factory BMW speakers are rated to handle. Careless tuning could mean damaging your car's sound system. We always advise using our prepared tuning files or having your DSP amplifier tuned professionally — leave DSP programming to the experts.

Experienced car audio enthusiasts, however, will always appreciate the extra power and versatility that comes from a programmable DSP.

Ready for a sound system upgrade in your car?  BimmerTech's Alpha One speakers and Premium Audio system DSP amplifier for BMW/MINI makes it easy.  Contact us to learn more.

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