The CL400 Classic represents the perfect balance between technical performance and affordability in the world of speaker cables. Designed by Norstone, a renowned French manufacturer with over two decades of experience, this 2×4 mm² conductor is aimed at enthusiasts of authentic sound and installations requiring high power. Its high-purity OFC copper construction and intelligent design make it a benchmark choice for efficiently connecting amplifiers and speakers in both home and professional setups.
Detailed Physical and Technical Description
The CL400 Classic features meticulous construction that reflects Norstone’s expertise in audio connectivity. Its transparent sheath, measuring 10×4 mm, immediately reveals the quality of the copper conductors inside. This transparency is not just aesthetic: it allows for visual inspection of the wire strands and facilitates quality control during installation.
The 2×4 mm² conductors are made from OFC (Oxygen-Free Copper) with an impressive purity of 99.997%. This near-absolute purity results from a specific smelting process that eliminates traces of oxygen, which are responsible for micro-bubbles and oxidation that degrade electrical properties. The finely twisted multi-strand wires optimize flexibility while maintaining conductive performance.
The most notable feature lies in the differentiated shape of the two conductors: one has a round cross-section, the other rectangular. This intentional asymmetry allows for instant identification of polarity without additional markings, reducing wiring errors and speeding up installation.
Electrical Performance and Built-in Technologies
With a linear resistance of only 0.006 Ω per meter, the CL400 ranks among the most conductive cables in its class. This low resistance is a direct result of the OFC copper’s purity and the generous 4 mm² cross-section per conductor. In practice, this allows for significant cable lengths—up to 60 meters—without noticeable signal degradation.
The capacitance of 73.480 pF/m remains within acceptable values for most amplifiers, even those most sensitive to capacitive loads. This measurement reflects the optimization of the internal geometry and the careful selection of insulating materials.
The OFC copper used offers superior conductivity compared to standard copper thanks to the near-total absence of oxygen. This purity results in better transmission of fast transients and a reduction in micro-distortions. Electrons flow more freely in this optimized crystalline structure, preserving the dynamics and nuances of the musical signal.
Advantages and Distinctive Features
The transparent sheath design is a major asset of the CL400. Beyond the practical aspect of polarity identification, this transparency allows for ongoing visual inspection of the conductors’ condition. Unlike opaque sheaths that can hide potential defects, the CL400 displays its quality openly.
The value for money is particularly attractive in the high-performance cable segment. Norstone manages to offer a high-purity OFC conductor at an accessible price, democratizing access to technologies usually reserved for premium ranges.
The remarkable flexibility makes installation easy in tight spaces. The multi-strand wires retain their suppleness even after numerous manipulations, a significant advantage when modifying installations or during moves.
French manufacturing guarantees strict quality control and complete traceability. Norstone relies on French expertise to maintain high standards while offering short delivery times.
What is the main difference between the CL400 and other models in the Norstone Classic range?
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The CL400 stands out with its 4 mm² cross-section, positioning it as the high-power model in the Classic range. Compared to the CL250 (2.5 mm²) and the CL150 (1.5 mm²), it offers lower linear resistance (0.006 Ω/m), allowing it to carry higher currents over longer distances. This larger cross-section makes it ideal for powerful speakers (over 150W) and installations requiring significant lengths, up to 60 meters. All models maintain the same 99.997% OFC copper quality and the differentiated shape polarity identification system, but the CL400 is the optimal choice for power-demanding systems.
Why choose an OFC copper cable over a standard cable?
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OFC (Oxygen-Free Copper) boasts a purity of 99.997% compared to about 99.9% for standard industrial copper. This difference results in higher electrical conductivity and reduced susceptibility to oxidation. In practice, OFC copper provides better transmission of fast transients, reduced micro-distortions, and greater long-term stability. Electrons flow more freely in this optimized crystalline structure, preserving the dynamics of the musical signal. This quality becomes especially noticeable in high-fidelity systems where every detail matters for sound reproduction.
What are the ideal applications for a 4 mm² cable like the CL400?
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The CL400 excels in several configurations: hi-fi systems with powerful floorstanding speakers (over 150W), home theater installations for front and center channels, professional sound reinforcement, and any connection requiring long cable runs (up to 60 meters). Its ability to carry high currents without significant loss makes it particularly suitable for powerful amplifiers and demanding speakers. Conversely, for compact speakers under 100W or distances less than 5 meters, a smaller cross-section may suffice and even be better suited to the system’s characteristics.
How do you identify and maintain polarity with the CL400’s identification system?
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The CL400 uses an innovative visual identification system: one conductor has a round cross-section while the other is rectangular, both visible through the transparent sheath. By convention, the round conductor generally corresponds to the positive (+) terminal and the rectangular to the negative (–). This identification should be maintained consistently throughout the installation: the same conductor shape on the positive terminals of both the amplifier and the speakers. This method eliminates common wiring errors found with cables marked only by lines or colors, speeds up installation, and ensures correct speaker phasing.
User reviews
Jacques
I had 2.5 cable that was over 20 years old. On my new amp, once I switched to this cable, I heard a clear difference on all the speakers. On the front speakers and the center, short cables, about 2m, I noticed better highs. On the rear speakers, long cables, about 15m, an improvement in the highs but also in power.
Comment from April 13, 2026 — Experience from April 02, 2026
Automatically translated — Show original (French)
J'avais du câble 2,5 qui avait plus de 20 ans. Sur mon nouvel ampli, une fois passé sur ce câble; j'ai entendu une nette différence sur toutes les enceintes. Sur les frontales et la centrale, câbles courts, environ 2m, j'ai perçu de meilleurs aigus. Sur les arrières, câbles longs, environ 15m, gain dans les aigus mais aussi dans la puissance.
Nicolas
Very good cable Doesn’t heat up and apparently conducts electricity well
Comment from December 25, 2025 — Experience from August 12, 2023
Automatically translated — Show original (French)
Très bon câble
Ne chauffe pas et conduit bien l'électricité apparemment
Michel
Very good product, a bit tricky to fit into banana plugs.
Comment from January 07, 2025 — Experience from December 26, 2024
Automatically translated — Show original (French)
Très bon produit un peu difficile à rentrer dans les fiches bananes.
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