The true wireless stereo (TWS) market is witnessing a significant evolution with the rise of hybrid designs featuring various drivers. In the market today we can find leading examples of designs that explore the various configurations of hybrid TWS earbuds, such as dual dynamic drivers, planar magnetic with dynamic drivers, combinations of MEMS speakers with dynamic drivers, and setups integrating balanced armatures (BAs) with dynamic drivers.
Evolution of Earbud Technology
TWS earbuds have progressed significantly from its early designs. Early earbuds, primarily dominated by single-driver systems, were simple and cost-effective but faced considerable limitations. They struggled to deliver the full range of the audible spectrum, often resulting in poor sound quality. This limited audio fidelity became increasingly apparent as consumer expectations for better sound experiences grew.
The introduction of multiple-driver systems marked a revolutionary change in earbud technology. By incorporating various types of drivers, hybrid designs could deliver vastly improved sound quality. These systems allowed for a richer, more detailed audio experience, catering to diverse listening preferences. This innovation was also crucial in meeting the growing consumer demand for high-resolution audio and features such as active noise cancellation (ANC), making premium sound more accessible to everyday users.
Despite these benefits, hybrid designs also brought new challenges such as miniaturization and integration complexities, increased costs, and the need to balance battery life with performance. Integrating multiple drivers into a compact form and housing additional components while maintaining comfort required for advanced engineering solutions.
Designing efficient crossover circuits to manage the audio signal division without compromising sound quality or ANC performance added further complexity. However, overcoming these challenges has enabled manufacturers to offer superior sound quality and advanced features, driving the widespread adoption of hybrid TWS earbuds in the market.
Market Trends Driving TWS
Hybrid designs have significantly enhanced audio experiences. According to SAR Insight & Consulting, more than 70% of devices using two or more speakers incorporate BAs, highlighting their growing popularity. Notable products leveraging hybrid technology with BA tweeters include the Edifier NeoBuds Pro 2, Bowers & Wilkins Pi7 S2, Fiio FW5 HiFi TWS earbuds, Meizu LIVE AI Hi-Fi Noise Cancelling, JBL Tour Pro 3, JLab Epic Sport ANC 3, and the JLab Epic Lab Edition earbuds. The JLab Epic Lab Edition earbuds set a new benchmark by being the first to be tuned to the Knowles Preferred Listening Response Curve, providing users with unparalleled crystal-clear sound.
As the market continues to evolve, hybrid TWS earbuds featuring BA tweeters are likely to set new standards in sound fidelity and user experience, driven by the technological innovations that have addressed previous limitations and provided richer, more detailed audio.
The TWS market’s competitive landscape continues to drive innovation. Each new generation of products introduces several new features, putting significant pressure on manufacturers to invest heavily in research and development to stay competitive. This competition has resulted in a rapid evolution of earbud technology, with brands striving to outdo each other by integrating cutting-edge technologies and enhancing user experiences. The race to deliver superior audio quality, longer battery life, more effective noise cancellation, and ergonomic designs ensures that consumers benefit from the latest advancements. As TWS innovators introduce new products, they set higher standards for the industry, encouraging continuous improvement and pushing the boundaries of what TWS earbuds can offer.
Designing TWS is a complex engineering challenge requiring in-depth knowledge across multiple domains and solid system-level acoustic expertise. While the top OEMs have big in-house engineering teams comprising hardware, software, algorithm engineers, and acoustic expertise, mid tier and smaller device makers face an uphill task to keep pace with innovation. Ground-up development can be expensive and prone to delays, making it difficult for smaller players to compete effectively.
To alleviate these pain points, several ODMs are developing complete hybrid TWS reference designs. For example, Fujikon, Grandson, OBO PRO2, Risuntek, and Siyoto demonstrated drop-in TWS reference design kits at CES 2024, showcasing the flexibility and ease of integration for TWS earbuds. These options help headphone brands quickly market wireless premium audio across various features, price points, and form factors.
Hybrid Design Configurations
While we at Knowles often talk about hybrid designs as combinations of dynamic drivers and BA drivers because that is what we are known for, hybrid TWS designs have evolved to incorporate various combinations of drivers to enhance sound quality and user experience.
There are several types of hybrid drivers used in audio technology, each combining different technologies to enhance the listening experience. Dual Dynamic Driver designs use two dynamic drivers to cover a wider range of frequencies, separating low and high frequencies for better audio clarity. Planar Magnetic and Dynamic Driver hybrids merge the detailed sound of planar magnetics with the powerful bass of dynamic drivers for a balanced and intricate audio profile. Another approach involves combining MEMS speakers with dynamic drivers, where MEMS provides precise high-frequency sounds and dynamic drivers handle the lower frequencies, resulting in a clear and dynamic sound experience.
The BA and Dynamic Driver hybrid design is favored by some for its ability to produce high-fidelity sound while maintaining robust bass response, creating a balanced and immersive sound environment. BA tweeters bring considerable value to hybrid TWS earphones by enhancing audio quality without the need for significant digital equalization. By extending the frequency response in TWS hybrid designs, BA tweeters contribute to superior sound quality, making them a key component in achieving Hi-Res certifiable designs.
BA tweeters also offer seamless integration with dynamic woofers, thanks to their customizable design options, such as adjustable port locations, coil impedances, and diaphragms. This flexibility is not commonly found in other tweeter technologies, making BAs particularly well-suited for hybrid configurations. Additionally, BA tweeters are equipped with a closed-back volume that isolates the sound from the rear of the diaphragm, preventing acoustic interference and degradation of system performance, a challenge often faced by other tweeter technologies with vented back volumes.
Regarding performance, BAs deliver more high-frequency output before reaching the driving voltage or distortion limit than any other type of tweeter, with an output range extending from 4kHz to 40kHz. This capability supports Hi-Res audio certification and ensures a clear and precise audio experience across the entire frequency spectrum.
The “constrained motion” diaphragm of BAs, where one end of the diaphragm is fixed, further reduces distortion spikes, enhancing overall audio clarity and detail. These characteristics, traditionally valued in hearing aids for their power efficiency, are equally beneficial in TWS applications, contributing to longer battery life and higher audio fidelity.
Market feedback and recent tech reviews indicate that TWS earbuds with extended frequency bandwidths are consistently rated higher for audio quality. The Knowles Preferred Listening Response Curve study highlights that listeners, regardless of age or hearing ability, prefer an expanded treble response beyond 10kHz for a more satisfying music experience.
BAs play a crucial role in helping TWS designers achieve these higher frequencies, aligning with the Knowles Curve to enhance music’s depth and richness. This preference is reflected in consumer tech reviews of TWS earbuds, such as the JLab Epic Lab Edition, which are tuned to the Knowles Curve. These reviews emphasize the superior output-to-size performance, power efficiency, and extended bandwidth that BA tweeters provide.
What Are the Challenges with Hybrid Designs?
Despite their advantages, hybrid designs come with their own set of challenges. One major issue is miniaturization and integration. Combining multiple drivers into a compact form factor that fits comfortably in the ear while housing other necessary components like batteries and ANC microphones requires intricate engineering and design.
This miniaturization often leads to higher costs compared to single-driver systems, as the production and assembly processes become more complex and require more precision. However, BAs mitigate some of these challenges through their flexible design, allowing for better placement of components within the earbud and improving overall performance. Additionally, the closed-back volume of BAs reduces the risk of acoustic response notches, ensuring a smoother audio experience even in complex crossover circuit designs.
Balancing battery life with performance is critical in wireless designs. Hybrid systems can demand more power, especially when supporting high-resolution audio and ANC, which necessitates innovative solutions to ensure long battery life without compromising performance.
Another significant challenge in hybrid designs is the complexity of crossover circuits. These circuits are essential for dividing audio signals appropriately between the dynamic woofer and the tweeter, ensuring that each driver operates within its optimal frequency range. Designing efficient crossover circuits that minimize phase shift and avoid interference between drivers adds to the technical complexity and development time.
Moreover, ensuring these circuits do not adversely impact ANC performance requires careful tuning and extensive testing. As a result, manufacturers must balance these technical demands with cost and design constraints to deliver high-quality TWS earbuds that meet consumer expectations.
The Balanced Armature Design Advantage
Designing TWS earbuds presents several challenges primarily driven by consumer expectations for high performance and features such as ANC, superior sound quality, and extended battery life. Achieving optimal sound quality in TWS earbuds is complex due to the need to balance multiple factors, including the integration of various technologies such as high-resolution Bluetooth audio codecs and hearing personalization. And delivering ANC requires a speaker that can produce high bass levels with minimal distortion, which typically calls for dynamic drivers. However, these dynamic drivers often compromise treble performance, especially in smaller sizes, which is crucial for high-quality audio and effective hearing personalization.
Hybrid designs that combine dynamic woofers with BAs offer a solution to these challenges. The dynamic woofers are excellent for producing the necessary bass for ANC, while the BA tweeters excel in delivering clear, high-frequency sound. This combination leverages the strengths of both types of drivers, allowing for enhanced sound quality across the audio spectrum without compromising on size or battery life. BA drivers are more efficient than dynamic drivers, consuming less power — a battery charge that lasts a full day in a device with one BA and one dynamic driver might only last a couple of hours in a device with two dynamic drivers. Dual dynamic drivers have been explored for in-ear earphones and IEMs, but the configuration was never viable in TWS earbuds for that reason.
Additionally, as discussed, BA tweeters provide more flexibility in earbud design, enabling better placement of components and improved overall performance. This approach not only supports the growing demand for premium sound quality and advanced features but also helps in creating more comfortable and longer-lasting TWS earbuds.
BAs also enable headphone brands to achieve higher frequencies necessary for optimal balanced audio performance. This brings depth and life to music without needing strong equalization, making them a great option for high-resolution music. Knowles RAN BAs deliver output up to 40kHz for JAS Hi-Res Audio certification and have high sensitivity, facilitating improved hearing personalization and enhancement. BAs offer improved fidelity, realism, and detail over traditional dynamic drivers and are incredibly small and lightweight, providing greater output with less power.
The Next Trends
According to Peter Cooney, founder of SAR Insight & Consulting, who began tracking hybrid designs entering the TWS market around 2019, as brands such as Amazon and Anker tested the market, hybrid earbuds have been expanding consistently. In 2020 he identified nine products from brands such as 1More, Amazfit, and QCY that had more than one driver, mostly using a dynamic driver and a BA. In 2021 he identified 11 products, all of which used a hybrid approach using a dynamic driver and a BA. Those included brands such as Bowers & Wilkins, Edifier, and Philips. Since then, SAR Insight observed brands including Huawei, Noble Audio, JBL, and JLab, entering the market with hybrid designs. Several brands have already launched their second or third products using dynamic + BA hybrid designs.
"TWS brands are using hybrid designs in their higher end products, focusing on audio quality as a key differentiator. Almost all these products to date have used a dynamic driver and BA hybrid design and we believe this approach will be increasingly used as it enables significantly improved audio playback," reported Peter Cooney. "Brands are also pairing higher quality audio codecs such as LDAC, LHDC and more recently LC3 to ensure high quality audio from the audio source through to the ear."
At Knowles, we’re seeing an increase in interest from many brands and expect to see new hybrid TWS models coming to market from prominent audio manufacturers in 2025. Hybrid designs have set new standards for sound fidelity and user experience and the technological innovations enabling these configurations are addressing previous limitations, providing richer and more detailed audio. As market trends continue to favor high-quality audio experiences, hybrid TWS earbuds are poised to become the new benchmark in personal audio devices. aX
This article was originally published in audioXpress, January 2025.
