Overview

The Sony ECR-500 electret condenser headphones were introduced in 1976, representing Sony’s early attempt at accessible electrostatic-like technology. Originally priced at 150 USD in 1976, these headphones featured Sony’s proprietary “pentagonal monocharge-electret diaphragm” with an unusual pentagonal shape designed to break up standing waves. The ECR-500 utilized unipolar electret technology, which required a specialized energizer/amplifier unit. While innovative for their era, these vintage headphones are now discontinued with no manufacturer support and suffer from inherent electret charge degradation over time.

Scientific Validity

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The Sony ECR-500 lacks comprehensive third-party measurement data for accurate evaluation. Available manufacturer specifications indicate 20Hz-20kHz frequency response with no deviation specified, distortion less than -50dB at adapter input 3 Vrms 1kHz, and maximum SPL of 120dB [1]. The electret technology inherently suffers from charge degradation over time, affecting long-term performance consistency. Without credible third-party measurements and applying conservative evaluation for non-third-party data, the product sits at problem level borderline across multiple indicators with 120dB maximum SPL at the problematic threshold.

Technology Level

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The ECR-500 featured Sony’s proprietary pentagonal monocharge-electret diaphragm technology, which was innovative for 1976. The unusual pentagonal shape was designed to break up standing waves, and the unipolar electret approach allowed for thinner diaphragms than conventional designs. However, evaluated from current technology standards, this represents outdated analog-only technology (-0.1) that lacks modern digital integration approaches. While the pentagonal diaphragm showed design innovation (+0.1), the electret technology itself has not progressed since the 1970s and is inferior to current electrostatic implementations, representing mature technology without competitive advantage duration.

Cost-Performance

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Current market prices for vintage ECR-500 units range from 62-400 USD depending on condition, with recent listings showing 62 USD on Yahoo Auctions. Products with equivalent-or-better basic headphone performance (20Hz-20kHz frequency response, 120dB max SPL capability) include the Koss KPH30i available at approximately 20 USD [6]. The KPH30i provides 15Hz-25kHz extended frequency response, 101dB sensitivity, 60Ω impedance, current production availability, and active manufacturer support [6]. Meeting ECR-500’s basic specifications while delivering broader frequency response and stable product supply. CP = 20 USD ÷ 62 USD = 0.3.

Reliability & Support

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The ECR-500 was discontinued in 1976, with no manufacturer support for nearly 50 years. Electret technology inherently degrades over time as the permanent charge dissipates, affecting long-term performance consistency. Vintage capacitors and internal components are prone to failure, and replacement parts are extremely limited. The wide stator spacing and high step-up ratio transformer design creates additional reliability concerns. The product requires specialized energizer/amplifier units that are themselves vintage and prone to failure, compounding reliability issues.

Rationality of Design Philosophy

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The ECR-500 represented Sony’s attempt at accessible electrostatic technology in the 1970s using electret compromise solutions. While the pentagonal diaphragm was an interesting innovation, the fundamental electret approach sacrificed long-term performance for reduced complexity compared to true electrostatic implementations. The design philosophy lacked measurement-focused scientific approach and relied on subjective analog approaches without comprehensive performance verification. From today’s perspective, the technology has shown no progression since 1976, and the electret approach has proven inferior to modern electrostatic and dynamic driver technologies that incorporate digital integration and advanced measurement techniques.

Advice

The Sony ECR-500 is a vintage curiosity with historical significance but cannot be recommended for practical use. Prospective buyers should consider modern alternatives like the STAX SRS-3100 complete system which offers superior performance, reliability, and manufacturer support at 800 USD versus 62 USD for ECR-500. The ECR-500’s electret technology is inherently degrading, requires rare vintage energizer equipment, and provides no technical advantages over current electrostatic technologies. These headphones may appeal only to vintage audio collectors interested in 1970s Sony engineering, but users seeking actual listening performance should avoid this outdated technology.

References

[1] HiFi Engine, “Sony ECR-500 Electret Stereo Headphone Manual”, https://www.hifiengine.com/manual_library/sony/ecr-500.shtml, accessed 2025-09-27 [2] STAX Headphones, “STAX SRS-3100 Electrostatic Earspeaker System”, https://staxheadphones.com/blogs/news/stax-srs-3100-electrostatic-earspeaker-system-sr-l300-srm-252s, accessed 2025-09-27 [3] HifiShark, “Used sony ecr-500 for Sale”, https://www.hifishark.com/search?q=sony+ecr-500, accessed 2025-09-27 [4] US Audio Mart, “Rare Sony ECR-500 Vintage Electret Headphones”, https://www.usaudiomart.com/details/649620402-rare-sony-ecr-500-vintage-electret-headphones/, accessed 2025-09-27 [5] Audiophile Style, “Review | Stax SRS-3100 Electrostatic Headphone System”, https://audiophilestyle.com/ca/reviews/review-stax-srs-3100-electrostatic-headphone-system-r977/, accessed 2025-09-27 [6] Koss Corporation, “KPH30i On-Ear Headphones”, https://koss.com/products/kph30i, accessed 2025-09-27

(2025.9.27)