Laptops 101: Designing a capable laptop audio subsystem

Speakers are often an afterthought in the grand scheme of things during a laptop purchase, with most of the focus being on the CPU, GPU, RAM, storage, and display quality. Most laptop makers offer devices with mediocre tinny speakers knowing that users would anyhow use wired or wireless headphones. Discerning users even go to the extent of using a dedicated USB DAC/Amplifier to get much cleaner sound than what the onboard audio can provide. 

Several reasons contribute to the use of mediocre speakers in a laptop, the primary reason being cost-cutting. OEMs tend to save the costs of developing good speakers to put towards other components that tend to impact purchase decisions. The space constraint within a laptop is also another factor. In the never-ending quest for thinness, it becomes all the more difficult to have thumping subwoofers and good mid-range drivers in an average current laptop chassis. 

Notebookcheck readers will know that we test out the sound signature as well in our reviews to get an idea about the frequency ranges covered by the laptop's onboard speakers. In this article, we will take a look into how laptop speakers are designed and how they work. We will also look into what goes into delivering good headphone audio and some of the software enhancements that work in tandem with the hardware. We illustrate these by taking examples of sound design in MSI gaming laptops. 

Check out our previous Laptops 101 topics below:

• Understanding what goes into designing an efficient laptop cooling solution

You could use headsets or external speakers to get better audio but onboard speakers are still an important consideration during a laptop's design. Factors such as the size and placement of the speaker units, the types of speakers that can be accommodated, the circuit design, and the frequency response play an important role in extracting the best possible audio. Let's have a brief look at each of them. 

Danish company Dynaudio provides some of the finest acoustics technology in the world for a variety of audio applications. Dynaudio-designed speakers provide a more natural sound reproduction than conventional ones. MSI has been working with Dynaudio since 2009 to elevate the audio experience on its gaming notebooks and this collaboration helps in deciding the choice and positioning of speakers during the design stage itself.

Typically, most notebooks have one speaker towards each side. While some of the better notebooks can reproduce the mids and highs in an acceptable manner, they struggle with low frequencies. Also, it is not easy to simply incorporate a woofer in such designs as the already thin chassis leaves little room for the cones to move enough air. So the only way to improve audio fidelity and get a near-flat frequency response is to maximize the area available to allow for a pair of woofers and two speakers. 

Back during CES 2015, Texas Instruments demonstrated something called a Smart Amp. Put simply, what Smart Amp does is that it allows the speakers to output more power without damaging them. Most laptop speakers are capped at 2 W even though they are theoretically capable of outputting 10 W or even 30 W. This is deliberately done to prevent damage due to excess current flowing through the coil and to avoid clipping artifacts. With Smart Amp, it is possible to dynamically filter out only those specific set of frequencies that cross a safe level instead of the entire waveform. 

Deriving a proper low frequency response is a challenge given the constraints in a typical laptop chassis. To alleviate this problem, passive radiators are used. A passive radiator is just a speaker without the innards. You get the cone, suspension, and the frame sans the electromagnetic apparatus. The advantage of using a passive radiator is that it offers a low frequency response comparable to a much larger bass reflex. 

In our own review of the MSI GT76, we found that the frequency response is excellent with a high 90 dB maximum volume. Although it sounded a bit muffled and could do better with the lows and mids, there is no doubt that the GT76 boasts an impressive performance that very few laptops can stake claim to. 

While enhanced audio through the onboard speakers is a good thing to have, most users inevitably use headsets for an immersive gaming experience. Thus, the components involved in headset audio must be of a high quality to get a high signal-to-noise ratio (SNR) and good performance for voice communication. 

Discerning audiophiles would attest to the importance of having a good circuit design for high-res audio output. A good circuit design ensures minimal signal loss and less static noise for a greatly enhanced listening experience. A lot goes into the actual PCB design as well. 

Apart from the ground plane, several other measures also help in getting a much cleaner audio output. These include:

• Short ground connections without shared vias.
• Keeping op-amp feedback paths as close to the op-amp as possible.
• Ensuring every op-amp and audio chip has decoupling capacitance on its power supply right next to the power supply pins.
• Short and clean audio path between the audio chip and the op-amp stage (audio path after the op-amp is not that critical).
• Separating digital circuitry from analog circuitry. 
• Using gold-plated audio connectors to minimize signal loss. 

So far, we've seen what goes into deciding the type of speakers, their placement, and how the audio circuitry is designed to maximize headset audio performance. Quality hardware needs to be supported by equally competent software and this is where audio solutions such as Nahimic come in. In this section, we will have a brief look at how Nahimic enhances the overall audio experience on your existing speaker or headset setup.

Most games (and multimedia software) use the Windows default sound settings to deliver audio. That means if you have a stereo headset and it is configured so in Windows, multi-channel audio will be down-mixed to stereo channels and you will lose out on spatial sound information like an enemy sneaking up behind you, for example.