Overview

The Fostex PM0.4c is a compact 2-way active desktop monitor with a 4-inch glass-fiber woofer and 19 mm soft-dome tweeter. Manufacturer specifications list a 60 Hz–20 kHz playback band, a 1.6 kHz crossover, 30 W + 30 W rated output, and RCA line inputs (320 mV sensitivity). The model is discontinued (“Black: Discontinued, while supplies last”), which impacts availability and long-term support compared with current production models [1][2].

Scientific Validity

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Within the intended nearfield use, catalog data indicate adequate performance but limited extension and output. Manufacturer specs: 60 Hz–20 kHz response, THD < 0.05% at 2 W, 1.6 kHz crossover, and RCA-only inputs [1]. Maximum SPL and comprehensive third-party anechoic measurements are not published, constraining certainty for high-level monitoring. Given the known constraints for 4-inch two-ways and absent independent full-band data, a conservative score is warranted pending robust external measurements [1].

Technology Level

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The PM0.4c employs a conventional 2-way topology with standard materials and a basic feature set. The rated 30 W + 30 W amplification and RCA-only connectivity reflect an entry-level design without notable innovations versus modern peers that add balanced inputs and DSP utilities [1]. No public white papers or patents are associated with this model; measured-performance leadership is not claimed.

Cost-Performance

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Current representative new price for PM0.4c is 329.99 USD [3]. The cheapest equal-or-better alternative we identify is Edifier’s MR4, widely available at 139.99 USD with balanced TRS/RCA/AUX inputs and third-party measurements showing competent response and low distortion for the class [4][5][6][8].
CP = 139.99 USD ÷ 329.99 USD = 0.424 → rounded to 0.4.
Equivalence note: MR4 provides equal user-facing functions (powered stereo monitor pair) and, per independent tests, demonstrates controlled on-axis response and benign directivity, with lower noise/connectivity advantages over PM0.4c’s RCA-only input [5][6][8].

Reliability & Support

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Fostex lists PM0.4c as discontinued; the product page also flags limited remaining stock [1][2]. While Fostex historically offers reasonable service for active products, discontinuation typically reduces parts availability and factory support horizons versus current models, lowering long-term ownership confidence.

Rationality of Design Philosophy

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Positioning the PM0.4c as a “personal” nearfield monitor is coherent, prioritizing compact size and straightforward operation. However, the design omits features now common even at low prices (e.g., balanced inputs, DSP presets), and subsequent market evolution produced comparably priced models with better connectivity and measured behavior. The approach is sensible but not forward-looking.

Advice

Avoid purchasing the PM0.4c new unless heavily discounted. As a discontinued model at 329.99 USD [3], it is out-valued by Edifier’s MR4 at 139.99 USD (about 58% lower price) with balanced I/O and solid measured performance and availability [4][5][6][8]. Other active, current 4-inch options include PreSonus Eris E4.5 (~157.99 USD, 2-way, 50 W class, broad retailer support) and Mackie CR4-X (typically 129.99–149.99 USD in the US market), both offering ongoing production and support [7][9][10].

References

[1] Fostex, “PM0.4c (Product Page, EN/JP),” https://www.fostex.jp/en/products/pm0-4c/, accessed 2025-08-16.
[2] Fostex, “Discontinued Products – PM Series (includes PM0.4c),” https://www.fostex.jp/en/discontinued-products/, accessed 2025-08-16.
[3] B&H Photo, “Fostex PM0.4c Personal Active Speaker System (Black),” https://www.bhphotovideo.com/c/product/1313096-REG/fostex_pm04c_b_2_way_studio_monitor_with.html, accessed 2025-08-16.
[4] B&H Photo, “Edifier MR4 Active 4 inch Studio Monitor Speakers (Black, Pair),” https://www.bhphotovideo.com/c/product/1900810-REG/edifier_mr4_black_mr4_active_4_42w.html, accessed 2025-08-16.
[5] Erin’s Audio Corner, “Edifier MR4 – Measurements/Review,” https://erinsaudiocorner.com/loudspeakers/edifier_mr4/, accessed 2025-08-16.
[6] Audio Science Review, “Edifier MR4 Review (Budget Monitor),” https://www.audiosciencereview.com/forum/index.php?threads/edifier-mr4-review-budget-monitor.29068/, accessed 2025-08-16.
[7] PreSonus Store, “Eris E4.5 Studio Monitor – Regular price 157.99 USD,” https://www.presonus.com/products/eris-e45-studio-monitor, accessed 2025-08-16.
[8] Edifier Global, “MR4 Powered Studio Monitor – Features/Connectivity,” https://www.edifier.com/global/p/studio-monitors/mr4, accessed 2025-08-16.
[9] Klarna (US), “Mackie CR4-X – Price overview (lowest 129.99 USD),” https://www.klarna.com/us/shopping/pl/cl267/5233048/Speakers/Mackie-CR4-X/, accessed 2025-08-16.
[10] Music Center Inc., “Mackie CR4-X (Pair) – 149.99 USD (sale),” https://www.musiccenterinc.com/shop/Keyboards/Recording/Reference-Monitors/p/Mackie-CR4-X-4-Multimedia-Studio-Monitors-Pair.htm, accessed 2025-08-16.

(2025.8.16)