Overview

The C5 Coax combines a 6″ coaxial driver (Kevlar woofer + 1″ fabric dome) with FIRTEC™ amplitude/phase linearization and an FIR crossover in a sealed enclosure. The manual lists 48Hz–22kHz (±3dB), per-unit measurement/compensation, and 6-band PEQ / delay via the optional KSD-RC[1]. New units are available from EU retailers at USD 2,278 per pair (USD 1,139 each)[3].

Scientific Validity

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Comprehensive third-party datasets are scarce, but Sound & Recording documents lab measurements with a B&K 4939 (¼″) at 96k/24-bit; >100Hz free-field and <100Hz near/far-field combination. The –6dB point ≈ 51Hz and –6dB beamwidth ≈ 115° (1–10kHz) are consistent with the maker’s claim and coaxial behavior[2]. Lack of public high-SPL distortion/polars caps the score at 0.6.

Technology Level

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FIRTEC™ linearization, per-unit calibration, a robust cabinet, and FIR XO with 6-band PEQ/delay via KSD-RC indicate solid execution[1][3]. Public, state-of-the-art wide-angle polars and high-level distortion evidence remain limited.

Cost-Performance

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Comparator (cheapest equal-or-better, pair): IK Multimedia iLoud MTM MKII — USD 799.99/pair. It offers ARC auto-calibration, linear-phase behavior, and Klippel NFS data showing F6 ≈ 49.1Hz and ≈ ±2.2dB flatness from 300–5kHz[4][5].
Target price (pair): USD 2,278[3].
Calculation: 799.99 ÷ 2,278 = 0.351… → 0.4.

Reliability & Support

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Per-unit calibration suggests strong QC[1]. EU channels sell new units and advertise 3-year store warranty[3]. Global availability and official web presence are limited, so regional service access should be considered.

Rationality of Design Philosophy

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A coaxial point source + FIR linearization targets time alignment and imaging — a sensible goal[1]. Given cheaper alternatives with auto-calibration and published NFS data, the market positioning is only moderately rational.

Advice

If you value coaxial time-alignment and the C5’s voicing/build, it’s credible. For most buyers prioritizing repeatable room integration and value, iLoud MTM MKII (pair USD 799.99) is the rational first pick. If choosing the C5, plan on measurement-guided setup and KSD-RC to unlock full control.

References

[1] KSdigital GmbH, “C-REFERENCE MANUAL (C5/C8/C88)” — FIRTEC, FIR XO, specs. https://cdn.korn.eu/documents/product/262099_m.pdf (accessed 2025-08-19)

[2] Sound & Recording (DE), “KSdigital C5-Reference – measurements” — B&K 4939, 96k/24b; >100Hz free-field; <100Hz combined; –6dB ≈ 51Hz; –6dB beamwidth ≈ 115°. https://www.soundandrecording.de/equipment/ksdigital-c5-reference-nearfield-monitor-mit-firtec-im-test/ (accessed 2025-08-19)

[3] MUSIC STORE professional (US view), “KS-Digital C5-Reference (Single)” — USD 1,139 each (pair USD 2,278 equivalent), 3-Years Warranty noted. https://www.musicstore.com/en_US/USD/KS-Digital-C5-Reference/art-REC0013311-000 (accessed 2025-08-19)

[4] IK Multimedia News, “iLoud MTM MKII — pricing” — Single USD/EUR 399.99; Pair USD/EUR 799.99 (excl. taxes). https://www.ikmultimedia.com/news/?id=iLoudMTMMKIIAnnounced (accessed 2025-08-19)

[5] spinorama.org (Erin’s Audio Corner), “IK Multimedia iLoud MTM MKII — Klippel NFS” — F6=49.1Hz; flatness ≈ ±2.2dB (300–5kHz). https://www.spinorama.org/speakers/IK%20Multimedia%20iLoud%20MTM%20MKII/ErinsAudioCorner/index_eac.html (accessed 2025-08-19)

(2025.8.20)