18 Sound 15NCX750H – Asymmetric-Dispersion 15-Inch Neodymium Coaxial with 70° × 50° Coverage and 109 dB HF Sensitivity
The 18 Sound 15NCX750H is the asymmetric-dispersion variant of 18 Sound’s lightweight 15-inch coaxial platform. Where the 15NCX750 produces an 80° conical pattern — the same angle in every direction — the 18 Sound 15NCX750H produces a 70° × 50° asymmetric pattern that provides wider horizontal coverage than vertical, matching the directivity behaviour of conventional horn-loaded two-way systems while retaining the coaxial architecture’s point-source coherence.
The 70° × 50° pattern changes who this coaxial is for. A conical 80° pattern is ideal for stage monitors where the performer needs equal coverage in every direction. The 18 Sound 15NCX750H’s asymmetric 70° × 50° is ideal for front-of-house PA, side-fill, and installed sound — applications where the audience occupies a wider horizontal area than vertical and where tighter vertical control reduces ceiling and floor reflections.
The HF section delivers 109 dB sensitivity — 1.5 dB above the 15NCX750’s 107.5 dB. The higher HF sensitivity is a consequence of the different exit profile and waveguide geometry that produces the asymmetric pattern. The tighter coverage concentrates more HF energy into the listening window, which raises the sensitivity within that window. For PA applications where the compression driver needs to project into the audience, the 18 Sound 15NCX750H’s 109 dB HF output provides more reach and presence than the 15NCX750’s conical dispersion can deliver.
18 Sound recommends enclosures as compact as 40 litres — half the 15NCX750’s 80-litre recommendation. The same T/S parameters (Qts 0.37, Fs 49 Hz) work in the smaller cabinet because 18 Sound tested and validated the 40-litre alignment specifically for the H variant. At 5.3 kg with the same 393 mm overall diameter, 360 mm baffle cutout, and 185 mm depth as the 15NCX750, the 18 Sound 15NCX750H fits the same cabinets with the option of building significantly smaller enclosures.
A dedicated passive crossover — the XVR15XCR00 — makes the 18 Sound 15NCX750H a ready-to-use transducer system, removing the complexity of custom crossover design for builders and installers.
Design and Construction of the 18 Sound 15NCX750H
The 18 Sound 15NCX750H shares the 15NCX750’s core platform — the same 75 mm copper ISV voice coil, the same aluminium SDR demodulating ring, the same single neodymium magnet motor, and the same basic chassis. The differences are in the HF section’s waveguide geometry and the resulting dispersion pattern.
The LF section uses the same 75 mm (3-inch) copper ISV coil that the 15NCX750 employs. The ISV architecture places conductor on both inner and outer surfaces of the former, creating the mass-balanced coil that delivers linear motor behaviour. The copper winding sustains the 400 W AES / 800 W program power rating. The aluminium SDR reduces flux modulation during excursion, keeping harmonic distortion low at higher power levels.
The 18.5 Tm force factor driving the 80.6 g moving mass produces 97 dB sensitivity and 4.1% reference efficiency. The 1 dB lower LF sensitivity compared to the 15NCX750’s 98 dB reflects the different cone profile optimised for the asymmetric HF waveguide — the cone acts as part of the HF horn, and the geometry changes needed for asymmetric dispersion slightly affect the LF acoustic behaviour.
The 50 Hz – 4700 Hz LF bandwidth is wider than the 15NCX750’s 55 Hz – 4500 Hz in both directions. The H variant reaches 5 Hz deeper into the bass and 200 Hz higher into the upper mid-range. The wider bandwidth provides more overlap with the HF section through the crossover region, which contributes to the smoother crossover transitions that 18 Sound’s coaxial architecture is designed to deliver.
The curvilinear LF cone uses 18 Sound’s high-damping pulp composition with water-repellent treatment. The cone profile is specifically shaped to work as a waveguide for the HF exit — and in the 18 Sound 15NCX750H, this cone-as-waveguide geometry produces the asymmetric 70° × 50° dispersion rather than the conical 80° pattern.
The HF section uses the same 64 mm (2.5-inch) EWAL (Edge-Wound Aluminium) voice coil, the same titanium diaphragm with Nomex bent edge former, and the same copper sleeve on the pole piece as the 15NCX750. The proprietary 3P hybrid radial tangerine phase plug produces smooth, coherent wavefronts with low distortion and high manufacturing consistency.
The difference is the HF exit profile. The 18 Sound 15NCX750H uses a specific exit geometry that shapes the compression driver’s output into the asymmetric 70° × 50° pattern as it couples with the cone-waveguide. The tighter pattern concentrates more HF energy into the listening window, which is why the 18 Sound 15NCX750H achieves 109 dB HF sensitivity versus the 15NCX750’s 107.5 dB — 1.5 dB more output within the coverage area from the same compression driver platform.
The 109 dB HF sensitivity matches the 15NCX910BE’s beryllium-equipped HF section. The 18 Sound 15NCX750H achieves this sensitivity from a titanium diaphragm through concentration rather than diaphragm efficiency — the tighter asymmetric pattern focuses the available energy into a smaller coverage window, raising the SPL within that window.
At 5.3 kg, the 18 Sound 15NCX750H is 400 g heavier than the 15NCX750’s 4.9 kg. The additional mass likely comes from the modified HF exit profile and waveguide geometry. The overall diameter (393 mm), baffle cutout (360 mm), depth (185 mm), and flange thickness (14 mm) remain identical — the two drivers are physically interchangeable in the same cabinet.
Performance and Applications for the 18 Sound 15NCX750H
The 18 Sound 15NCX750H delivers 97 dB LF sensitivity from 50 Hz to 4700 Hz and 109 dB HF sensitivity from the 1.2 kHz crossover point upward. The 12 dB sensitivity difference between sections is managed through the crossover network, with the HF section padded to match the LF output level.
The 70° × 50° asymmetric dispersion is the specification that defines the 18 Sound 15NCX750H’s application space. The 70° horizontal provides wide enough coverage for small to mid-sized venues from a single cabinet, while the 50° vertical focuses energy on the audience plane with more precision than the 15NCX750’s 80° conical pattern. The tighter vertical control reduces ceiling and floor reflections, improving the direct-to-reflected sound ratio in the listening area.
The asymmetric pattern is what PA cabinets and installed speakers need. In a stage monitor, the performer sits at one angle relative to the speaker. In a PA cabinet, the audience spans a wide horizontal area at various vertical angles — wider horizontal and tighter vertical is the geometry that covers the most listeners with the most consistent tonal balance. The 18 Sound 15NCX750H’s 70° × 50° provides this while maintaining the coaxial advantage of point-source coherence — no lobing, no comb-filtering at the crossover, no coverage discontinuities between the LF and HF sections.
The 109 dB HF sensitivity provides the HF projection that front-of-house PA applications demand. The 1.5 dB advantage over the 15NCX750’s 107.5 dB translates to roughly 40% more HF acoustic power in the coverage window. For venues where the audience is distant from the speakers and atmospheric absorption attenuates high frequencies, the 18 Sound 15NCX750H’s higher HF sensitivity ensures the treble reaches the back row with presence and definition.
The 40-litre minimum enclosure recommendation is remarkable. The 15NCX750 recommends 80 litres. The 18 Sound 15NCX750H works in cabinets half that size. For compact PA tops and lightweight portable systems, a 40-litre enclosure with a 15-inch coaxial at 5.3 kg produces a complete two-way point-source speaker system in a package that rivals 12-inch two-way cabinets on size and weight.
The Thiele–Small parameters are essentially identical to the 15NCX750 — same Qts (0.37), same Fs (49 Hz), same EBP (122 Hz), same Xmax (5.5 mm). The 0.37 Qts provides the same sealed/vented enclosure flexibility. In a 40-litre vented cabinet, the alignment produces punchy, well-controlled mid-bass. In larger sealed or vented enclosures, the response extends deeper with more output below 80 Hz.
The 400 W AES / 800 W program LF power handling and 70 W AES / 140 W HF power handling match the 15NCX750 exactly. The power handling is adequate for compact PA and stage monitoring at moderate to high output levels.
The dedicated XVR15XCR00 passive crossover provides a ready-to-use crossover solution — a different part number from the 15NCX750’s XO15NCX, reflecting the different HF sensitivity and exit profile that require adjusted crossover component values. Builders using the passive crossover get a factory-designed, tested filter matched to the 18 Sound 15NCX750H’s specific LF/HF sensitivity balance and dispersion characteristics.
The choice between the 18 Sound 15NCX750H and the 15NCX750 comes down to dispersion and application. The 15NCX750’s 80° conical pattern covers equally in every direction — ideal for stage monitors and applications where the listener’s position relative to the speaker is unpredictable. The 18 Sound 15NCX750H’s 70° × 50° asymmetric pattern provides wider horizontal and tighter vertical — ideal for PA tops, side-fill, installed sound, and any application where horizontal coverage and vertical control define the system’s effectiveness.
Conclusion – 18 Sound 15NCX750H Coaxial Driver
The 18 Sound 15NCX750H is the PA-optimised variant of 18 Sound’s lightweight 15-inch coaxial platform. The 70° × 50° asymmetric dispersion replaces the 15NCX750’s 80° conical with the wider-horizontal, tighter-vertical pattern that front-of-house PA and installed sound applications require. The 109 dB HF sensitivity — 1.5 dB above the 15NCX750 — provides the treble projection that PA needs to reach the audience at distance.
The shared platform means the same ISV voice coil, the same SDR distortion reduction, the same EWAL titanium compression driver, and the same T/S parameters. The same 393 mm diameter, the same 360 mm cutout, the same 185 mm depth. The two drivers are physically interchangeable — one cabinet platform, two dispersion options.
The 40-litre minimum enclosure is the practical advantage that makes the 18 Sound 15NCX750H exceptional for compact PA design. A 15-inch coaxial point source in a 40-litre cabinet at 5.3 kg competes with 12-inch two-way systems on size and weight while delivering 15-inch bass output and coaxial coherence. The XVR15XCR00 passive crossover completes the package for builders who want a factory-designed, ready-to-use system.
For compact PA tops, side-fill cabinets, installed sound, and any application where a 15-inch coaxial needs asymmetric dispersion with maximum HF sensitivity from the lightest possible package, the 18 Sound 15NCX750H is the coaxial that gives PA designers the coverage pattern they need while keeping point-source coherence that discrete two-way systems can’t match.
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About 18 Sound
18 Sound products are proudly made in Reggio Emilia, Italy, combining advanced technology with Italian craftsmanship. Known for their high-performance professional audio components, 18 Sound is a trusted name in the global audio industry. Their state-of-the-art manufacturing and strict quality control ensure exceptional reliability and sound clarity. 18 Sound products are designed to meet the demands of speaker builders and audio professionals, 18 Sound offers premium products with outstanding value and performance worldwide.
