The Stax SR-Lambda Pro, also known as the SR-Λ Pro, is an electrostatic ear speaker that was released in 1982, marking it as the second model in the Lambda series produced by Stax. Unlike traditional headphones, these electrostatic ear speakers require a dedicated amplifier to operate efficiently, reflecting their unique design and performance characteristics. The SR-Lambda Pro features a 1.5-micron thick diaphragm and uses pro-bias technology (580V), offering a transparent and balanced auditory experience that is both fast and precise. Although constructed mainly from plastic, the Lambda Pro boasts a headband with a cloth suspension strap to aid in comfort and weight distribution. Despite being released over 40 years ago, they exhibit impressive durability and can still be found functioning well, showcasing the longevity of their build quality. The sound profile of the SR-Lambda Pro is characterized by tight and clean bass, a broadly accurate midrange, and pronounced treble, although the upper-treble can be fatiguing for some listeners. This model stands out with its open soundstage and exceptional transient response, making it well-suited for genres like electronic and acoustic music. However, the lack of warmth and mid-bass impact may not appeal to all audiophiles. Replacement parts for these ear speakers, such as the headband and ear pads, are still available, highlighting their continued support and availability in the market. Priced in the mid-fi segment, used units can typically be found between $250 and $350, excluding the necessary amplifier costs.
