What Is Digital Signal Processing (DSP) and How Does It Affect Audio?

Digital signal processing (or DSP) is a catchall term in the audio realm. Sometimes it refers to the process of converting an analog signal to a digital one. Other times it encompasses the gimmicky audio modes in a companion app for true wireless earbuds. In our reviews, the term typically refers to how headphones or speakers adjust an audio signal to ensure ideal sound at all volumes. But the specifics of DSP implementations can be quite murky and vary by the manufacturer. With that in mind, we’ve gathered everything you need to know about DSP here so you can make an informed buying decision.

How Does DSP Work and Sound?

DSP in wireless headphones and speakers primarily focuses on compressing or limiting the peaks of loud passages to prevent distortion. Imagine the audio signal as a sine wave: If the top of the sine wave crosses a certain threshold, it will distort. In applying dynamic compression, headphones and speakers seek to flatten the peak and keep it from crossing the distortion threshold. The higher your volume level is when you listen, the more likely it is that peak-limiting DSP will be in play—this is particularly true (or at least, more noticeable) with wireless speakers.

This can potentially happen multiple times or continuously throughout a track depending on its composition, the aggressiveness of your device’s compression, and your volume levels. Usually, bass frequencies—the deep lows and even the low-mids—are the most likely elements to trigger dynamic volume reduction. Of course, the specifics depend on the manufacturer and the frequency range of a particular product, but DSP will often simply lower the volume of only the powerful bass frequencies that are triggering it, so that the overall volume of the track remains loud.

If you have ever noticed a song on the radio that temporarily dips to a lower volume and then slowly rises again, you’ve heard an extreme form of dynamic compression. But it’s possible to apply and then release compression gradually so that the effect is much less jarring. An example would be a more subtle compression ratio in combination with an EQ profile that thins out the bass frequencies as described above. Most forms of DSP use some variation of that approach.

It’s easy to hear this effect in real time on plenty of headphones and speakers. Simply blast them at maximum volume (make sure to protect your ears) and you are likely to notice a distinct lack of bass in the mix.

Aside from preventing distortion, many manufacturers now also use DSP to boost bass depth (and occasionally the highs) when you listen at lower volumes. Remember the “loud” button on stereos and boomboxes? Some forms of DSP effectively do the same thing in these scenarios: They lend some extra emphasis to the lows. Some higher-end analog stereo gear might offer a knob for this function rather than a simple button, thus allowing a discerning listener to adjust the effect to taste. But that’s not possible on many consumer models, so you are largely stuck with how the manufacturer chooses to handle it digitally.

With all of this in mind, most consumer audio products that use DSP sound better and fuller at moderate-to-high volumes than at their maximum setting.

What Else Is DSP Useful For?

DSP can also refer to a wide range of sound effects in companion apps for consumer audio products. Do you see a Spatial Audio, Live, or 3D setting? Those all use audio processing to creative ends, adding in reverb or delay to replicate the sound of music in certain spaces. Apple’s spatial audio feature even tracks your head movements to make it seem like audio is emanating from a single point in the room, rather than your headphones.

Generally, these types of DSP modes are fun at best and harmful at worst, depending on how much you value an accurate presentation of sound. The important thing to note here, however, is that the goal of this type of DSP isn’t to prevent distortion or beef up the lows at lower volumes—it essentially changes the entire stereo mix.

Should You Avoid DSP?

The most frustrating part of DSP is that it largely operates behind the scenes. At its worst, it lurks in the background, like a demon behind the drivers, tweaking your audio however it sees fit and rarely delivering a truly transparent signal. Similar to how a new paint job can’t fix a dent in your car, even EQ adjustments can’t fully counteract heavy doses of DSP.

Audio-Technica’s wired ATH-M50x headphones give equal attention to the lows, mids, and highs, which makes them ideal for studio use
(Credit: Tim Gideon)

The vast majority of manufacturers don’t let you simply turn off DSP (save for whatever sound effects you can simply ignore in a companion app) to prevent you from using a product beyond its intended purposes. Another reason is that DSP is a secret sauce. Every company ostensibly uses a proprietary DSP implementation, even if the resultant audio sounds similar.

Sound engineers work hard to produce mixes that sound just right, and the worst DSP bulldozes over that effort—particularly at high volume levels. Audiophiles who want to hear what the sound engineers intended—and not what a manufacturer thinks will appeal to the masses or keep its drivers from distorting—should steer clear of DSP if possible.

How can you avoid DSP? Buy some wired headphones or speakers—DSP is generally the norm in wireless audio, while the opposite is true for wired audio. Often, manufacturers that avoid DSP proudly display that fact on their marketing material because they know some people seek that quality specifically. You don’t even need to spend exorbitant amounts of money—some of our favorite audiophile and studio headphones cost less than $250.

That said, most people can live with DSP just fine. As mentioned, many popular audio products simply use DSP to ensure that music sounds good at every volume and nothing more nefarious. The resultant audio profile might not be completely accurate, but that’s likely not a deal breaker for many listeners.

For more on how to get the best sound quality from your headphones or speakers, see our stories on Bluetooth codecs, equalizers, and hi-res audio.