Overview

The Altec 620A is a professional monitor speaker manufactured in the 1970s, featuring a bass-reflex enclosure with a 38cm diameter 604-8G coaxial driver. It boasts a frequency response of 20Hz-22kHz and maximum output of 103dB, and was known as an industry standard used in broadcasting stations and recording studios. The 604-8G driver features a unique design where the high-frequency horn throat passes through the center of the low-frequency magnetic circuit, designed to achieve excellent resolution even in demanding monitoring environments with four or more channels of overlapping audio. The original price in 1977 was 358,500 JPY per unit.

Scientific Validity

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Compared to modern measurement standards, the 620A’s performance deviates significantly from contemporary transparency levels. The nominal 20Hz-22kHz frequency response shows deviations far exceeding the modern ±3dB standard, particularly notable in the constraints of cabinet design for low-frequency reproduction. Considering the 1970s technology level, detailed measurement data for S/N ratio, THD, and crosstalk are difficult to obtain, but they are estimated not to reach modern standards of 105dB+ S/N ratio or 0.01% THD. While the 604-8G driver’s materials technology and magnetic circuit design were advanced for their time, transparency in the audible range is clearly inferior when compared to the latest digital technology.

Technology Level

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The coaxial design represents a rational approach to achieving point source characteristics, and the 604 series was recognized as an industry standard. However, when evaluated by modern technological standards, limitations in materials science, magnetic circuit design constraints, and immature diaphragm technology become apparent. While the 604-8G driver shows consideration for minimizing phase differences between the high-frequency compression driver and low-frequency woofer, the invested technology level remains moderate compared to modern DSP technology, high-performance magnetic materials, and lightweight, high-rigidity diaphragms. Patent and technical paper backing is also limited compared to contemporary products.

Cost-Performance

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Against the current market price of approximately 70,000 JPY per unit (140,000 JPY per pair), a Yamaha HS8 pair with equivalent or superior functionality and performance is available for about 75,000 JPY. The calculation yields 75,000 JPY ÷ 140,000 JPY = 0.535, which is rounded to 0.5. The 620A remains at 1970s technology levels and significantly underperforms the HS8’s flat 38Hz-30kHz frequency response, built-in 75W+45W bi-amp configuration, and modern S/N ratio and THD performance in all measurable aspects. Furthermore, since the HS8 is an active speaker with built-in amplification, it has a significant advantage in total system cost compared to the 620A, which requires a separate amplifier. In terms of pure performance-to-price ratio, the 620A fails to meet modern standards, with actual cost-performance around 0.5.

Reliability & Support

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With approximately 50 years since manufacture, numerous reliability issues are expected including component aging, driver edge deterioration, and cone paper degradation. Official support from Altec has ended, requiring specialist technicians for repairs. Challenges in maintenance are serious, including difficulties in parts procurement, rising repair costs, and decreasing availability of qualified technicians. Significant reduction in Mean Time Between Failures (MTBF) due to aging requires substantial maintenance costs for continued use. Naturally, no warranty period exists, and all post-purchase failure risks must be borne by the purchaser.

Rationality of Design Philosophy

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While design philosophy aimed at sound quality improvement is recognized, scientific approaches based on measurement results were limited. Considering the technological constraints of the time, some decisions were rational, but from a modern perspective, inefficient investment in mass and neglect of measurement data are evident. The coaxial design itself is a rational concept for achieving point source characteristics, but ideal performance was not achieved due to technical constraints. Market pricing dependent on mythical vintage audio value contradicts scientific rationality. Modern technology has established methods to achieve equivalent functionality at lower cost, reducing the necessity for specialized equipment existence.

Advice

For those considering purchasing the 620A, we recommend first clarifying your purchase purpose. While understandable as a historical artifact or collector’s item, it cannot be recommended for practical music reproduction. Modern studio monitors such as the Yamaha HS8, Genelec 8020A, Adam Audio A5X, and Neumann KH80DSP exceed the 620A in all measured performance aspects. Considering maintenance costs, parts procurement difficulties, and failure risks, purchase for practical purposes is economically and technically irrational. For those genuinely seeking sound quality improvement, we strongly recommend investing in a modern studio monitor system within the same budget. If you absolutely must use the 620A, select a properly maintained unit and include regular professional maintenance costs in your budget.

(2025.7.26)