Overview

The KEF LSX II is a wireless active speaker system released by British manufacturer KEF in 2022. It features the 11th generation Uni-Q driver with a coaxial arrangement of a 19mm aluminum dome tweeter and a 115mm magnesium/aluminum alloy cone. The Class D amplification delivers 30W per channel for tweeters and 70W for woofers, supporting high-resolution streaming up to 24-bit/384kHz. It includes HDMI ARC, USB-C, and optical digital inputs, with wireless connectivity via AirPlay 2, Google Chromecast, and Bluetooth 4.2. The compact desktop bookshelf design incorporates digital signal processing for audio optimization.

Scientific Validity

\[\Large \text{0.7}\]

According to measurement data, the KEF LSX II achieves a frequency response of 54Hz-28kHz (±3dB) and demonstrates excellent phase characteristics through its coaxial Uni-Q driver. The coaxial arrangement reduces phase issues common in typical 2-way speakers, providing good sound image positioning. Class D amplification achieves low distortion rates, while the bi-amp design enables individual control of each driver. However, there is a sharp output drop above 23kHz, likely due to 48kHz sampling processing limitations. Due to physical constraints of the small enclosure, the low frequency response is enhanced by port tuning at 58Hz, though full-range reproduction has limits. Overall, considering size constraints, it shows good measurement results, but does not achieve complete transparency level.

Technology Level

\[\Large \text{0.8}\]

The KEF LSX II employs 11th generation Uni-Q driver technology, utilizing the acoustic advantages of coaxial arrangement. The W2 wireless streaming platform enables high-resolution support up to 384kHz/24-bit, with built-in DSP processing for sound quality correction. Each speaker contains 4 DACs (dedicated per driver) and achieves precise frequency division through digital crossover. The enclosure design has physical constraints due to miniaturization, with certain limits in resonance suppression. Class D amplification achieves high efficiency and low heat generation, with technically excellent design integrating multiple functions into a compact enclosure. However, the upper model LS50 series’ Metamaterial Absorption Technology (MAT) is not included, leaving room for improvement in technical completeness.

Cost-Performance

\[\Large \text{1.0}\]

The KEF LSX II, priced at approximately 1,400 USD, stands as one of the most cost-effective options for achieving high-fidelity sound in its category. To evaluate its cost-performance, a comparison with a system comprising a Wiim Pro Plus streamer (219 USD) and ADAM Audio A5X active speakers (600 USD each, 1,200 USD per pair) is appropriate. The total cost of this alternative system is 1,419 USD. Given that this price is nearly identical to the LSX II, the product is considered to offer top-tier cost-performance, earning a perfect score.

Reliability & Support

\[\Large \text{0.8}\]

KEF, as an established British audio manufacturer, maintains a long-term product support system. The LSX II comes with standard warranty coverage, with repair and support services provided through authorized dealers in Japan. As a wireless product, it supports firmware updates with continuous functional improvements and bug fixes. The adoption of Class D amplification suppresses heat generation, improving reliability for long-term use. While the complexity of digital signal processing circuits slightly increases failure risk, overall reliability is good with modern design. However, long-term compatibility maintenance of wireless streaming functions and continuous development/updates of dedicated applications depend on the manufacturer’s business continuity.

Rationality of Design Philosophy

\[\Large \text{0.7}\]

The KEF LSX II’s design philosophy adopts a modern approach of integrating high-end technology into a compact enclosure. The utilization of acoustic advantages through the coaxial Uni-Q driver is scientifically rational, and digital signal processing for sound quality optimization provides measurable improvements. The combination of Class D amplification and digital crossover is efficient, with 24-bit/384kHz high-resolution support providing theoretical sound quality improvement possibilities. However, it does not completely overcome low-frequency performance limitations due to physical constraints, and the absence of MAT technology used in upper models leaves room for improvement in technical completeness. While wireless function integration improves convenience, signal processing complexity also creates risks of sound quality degradation. Overall, it is based on rational design philosophy, but requires improvement in consistency with pricing.

Advice

The KEF LSX II is a technically outstanding wireless speaker in its price range. Its proprietary Uni-Q coaxial driver provides precise sound imaging, and its comprehensive connectivity, including AirPlay 2, Chromecast, and HDMI ARC, offers a significant advantage not easily found elsewhere. While various wireless speakers exist, there are almost no direct competitors that combine the same level of functionality with acoustic performance backed by objective measurement data. The value of the LSX II lies in the KEF brand’s reliability, sophisticated design, and the superior acoustic performance delivered by the Uni-Q driver. It achieves surprisingly high-quality sound from a compact enclosure, and its performance fully justifies the price. For users seeking authentic Hi-Fi sound in a space-saving form factor, it is one of the best choices available.

(2025.7.18)