Overview

The CW250D is a sealed active subwoofer with a 25 cm (10-inch) driver and a 300 W (JEITA/4 Ω) amplifier, positioned by Fostex as a “music-dedicated add-on subwoofer.” Manufacturer documentation cites a maximum output of 106 dB at 60 Hz (all-space), low-pass adjustment from 40–140 Hz, phase switch, and cabinet/baffle construction aimed at resonance control; production has ended. [2][3][4][5]

Scientific Validity

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There are no credible third-party lab measurements publicly available for CW250D. Manufacturer specs indicate: max SPL 106 dB/60 Hz (all-space, +6 dB floor), sealed acoustic-suspension design, crossover 40–140 Hz (12 dB/oct) with 36 dB/oct suppression above ~270 Hz, and claimed very-low-frequency capability (e.g., reproduction down to 32 Hz and “feel” at 16 Hz). These are manufacturer claims rather than independently verified data, so the score remains at the default midpoint pending measurements. [3][4]

Technology Level

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Engineering choices are above average: Motional Feedback (MFB) sensing on the woofer, a long-stroke 25 cm driver with Kevlar/BKP pulp diaphragm and a 1.1 T motor, a sealed cabinet, and a PWM amplifier. The baffle uses laminated camphor/eucalyptus plywood with MDF to balance stiffness and damping. While MFB is technically sophisticated, its audible advantage over well-executed conventional designs isn’t established here due to missing third-party data. [2][3][4]

Cost-Performance

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Market basis: 680 USD (current import/market price assumption for the review target). As the cheapest equal-or-better comparator, RSL’s Speedwoofer 10E offers a 10-inch sub, 300 W RMS amp, and anechoic 26–200 Hz (±3 dB) response at 339 USD—providing equal-or-better extension and output capability from a user-perspective.
CP calculation: 339 USD ÷ 680 USD = 0.498… → 0.5 (rounded to one decimal). [1]

(For context, SVS SB-1000 Pro—12-inch sealed, 325 W RMS, rated to 20 Hz—sells for 599.99 USD, but the CP score above is based on the single cheapest equal-or-better option as required.) [6]

Reliability & Support

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The owner’s manual specifies a 1-year warranty in Japan and a 6-year minimum parts retention period after production ends. Since CW250D is discontinued, long-term official support is inherently limited versus current models. No robust third-party failure-rate data is published. Score reflects below-average warranty length and end-of-production status. [4][5]

Rationality of Design Philosophy

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A sealed alignment with MFB and conventional low-pass management is a rational way to pursue accuracy. However, the “music-specialized” positioning provides no clear measurable advantage over modern, well-engineered subwoofers that target neutral reproduction for all content. Given today’s alternatives that match or exceed extension/output at lower prices, the design direction is only partly persuasive.

Advice

Unless you specifically need an MFB-equipped unit, current models deliver stronger value with clearer measurement backing. At 680 USD, CW250D is undercut by RSL Speedwoofer 10E (339 USD) and similar options while also benefitting from active production support. Consider CW250D only if you find it used well below ~340 USD or for interest in MFB experimentation; otherwise, choose a current model with documented performance and warranty. [1][6]

References

[1] RSL Speakers, “Speedwoofer 10E,” https://rslspeakers.com/products/rsl-speedwoofer-10e, accessed 2025-08-23. Frequency response and price noted.
[2] Fostex, “CW250D (EN product page),” https://www.fostex.jp/en/products/cw250d/, accessed 2025-08-23.
[3] Fostex Online Shop, “CW250D (JP) – specs/feature details,” https://store.fostex.jp/view/item/000000000071, accessed 2025-08-23. Crossover slopes, cabinet/baffle materials, 1.1 T motor, long-stroke claim, max SPL.
[4] Fostex, “Active Sub Woofer System CW250D – Owner’s Manual (JP PDF),” https://www.fostex.jp/wp/wp-content/uploads/CW250D_OM_J.pdf, accessed 2025-08-23. Warranty (1 year JP), max SPL, I/O, crossover range.
[5] Fostex, “Discontinued Products,” https://www.fostex.jp/en/discontinued-products/, accessed 2025-08-23 (CW250D listed).
[6] SVS, “SB-1000 Pro Subwoofer,” https://www.svsound.com/products/sb-1000-pro-subwoofer, accessed 2025-08-23.

(2025.8.23)