18 Sound 10W500 – High-Sensitivity 10-Inch Ferrite Woofer with Copper ISV Voice Coil and 98 dB Output
The 18 Sound 10W500 is the original high-sensitivity 10-inch ferrite woofer in 18 Sound’s range — delivering 98 dB sensitivity from a 51 mm copper ISV voice coil with 14.6 Tm force factor, 53 Hz Fs, and a 0.29 Qts that produces tight, motor-dominant bass in vented enclosures tuned as deep as 58 Hz. Where the 10W650 that replaced it shifted the design toward enclosure flexibility (0.48 Qts), wider bandwidth (5700 Hz), and SDR distortion reduction, the 18 Sound 10W500 prioritises raw output — 2 dB more sensitivity than the 10W650 from a copper ISV coil that generates 14.6 Tm of force factor.
The 98 dB sensitivity from a ferrite 10-inch is the highest of any ferrite 10-inch woofer in 18 Sound’s range. It approaches the neodymium Tetracoil 10NTLW2000’s 98.5 dB from a ferrite motor — only 0.5 dB apart. The copper ISV coil and 33 g moving mass produce a Bl/Mms ratio that extracts maximum output per watt from the FEA-optimised ferrite motor.
The copper winding is a specific material choice that the 10W650 doesn’t share. Where the 10W650 uses edgewound aluminium (EWAL), the 18 Sound 10W500 uses copper wire in the ISV architecture. Copper is denser and more electrically conductive than aluminium — providing lower DC resistance per unit of conductor length and better thermal conductivity. The copper ISV coil is the technology that defined 18 Sound’s compact two-way woofer philosophy before the EWAL edgewound designs replaced it.
18 Sound describes the 18 Sound 10W500 as the evolution of the 10W400, designed for compact bass reflex systems in enclosures as small as 25 litres. The 30-litre recommended enclosure tuned to 58 Hz targets deeper bass extension than the 10W650’s 25 litres at 70 Hz.
At 4.7 kg with weather-protected cone treatment, dampened linen triple roll surround, and 121 mm depth. 8 Ω only. 18 Sound lists the 10W650 as the alternative/current model.
Design and Construction of the 18 Sound 10W500
The 18 Sound 10W500 uses a 51 mm (2-inch) copper wire ISV (Interleaved Sandwich Voice Coil) wound on a high-strength fibreglass former. The ISV places conductor on both inner and outer surfaces of the former, creating a mass-balanced coil with symmetrical energy distribution. The copper winding provides lower resistance per unit of conductor length than the aluminium used on the 10W650’s EWAL coil, and better thermal conductivity for heat dissipation from the voice coil to the former and gap.
The 14.6 Tm force factor is 2.2 Tm higher than the 10W650’s 12.4 Tm — the copper ISV coil’s higher conductivity and the FEA-optimised ferrite motor’s flux concentration produce more force from the 51 mm format than the 10W650’s 65 mm EWAL generates. The 14.6 Tm driving 33 g of moving mass produces 98 dB sensitivity — 2 dB above the 10W650 and competitive with 18 Sound’s neodymium 10-inch range.
The 53 Hz Fs is 14 Hz lower than the 10W650’s 67 Hz, confirming the 18 Sound 10W500’s deeper bass alignment. The 0.29 Qts and 170 Hz EBP define a motor-dominant driver designed for vented enclosures — tight, well-damped bass response with fast transient recovery. The 10W650’s 0.48 Qts offers more enclosure flexibility but with less motor control per unit of Qts.
The dampened linen triple roll surround is a specific surround material shared with the 10MB400 mid-bass. The dampened linen controls vibration modes that generate mid-range coloration — the same bell-mode management approach applied through the surround’s material properties rather than through cone treatment alone. The triple roll geometry provides good travel control and linear excursion through the 5.5 mm Xmax.
Voice coil cooling uses fine air channels between the chassis back plate and the magnet top plate, drawing heated air from the voice coil gap and dissipating it through the chassis casting. 18 Sound developed this thermal architecture using 3D CAD resources. The top and back plates of the magnet assembly have been designed using in-house FEA CAD to optimise flux density and Bl factor in the air gap.
The curvilinear paper cone with weather-protected treatment provides outdoor durability. The 0.72 mH Le is slightly higher than the 10W650’s 0.59 mH — the 10W500 doesn’t carry the SDR demodulating ring that reduces the 10W650’s inductance. The ISV coil’s symmetrical winding provides some inductance linearisation, but without the SDR, the absolute inductance is higher.
At 4.7 kg, 260 mm overall diameter, 232 mm baffle cutout, 121 mm depth, and 14 mm flange thickness, the 18 Sound 10W500 is 400 g heavier than the 10W650 (4.3 kg) with a slightly different cutout (232 vs 230 mm) and thicker flange (14 vs 9 mm).
Performance and Applications for the 18 Sound 10W500
The 18 Sound 10W500 delivers 98 dB sensitivity across a 55 Hz – 4500 Hz bandwidth. The 98 dB is the highest of any ferrite 10-inch woofer in 18 Sound’s range — 2 dB above the 10W650 and 2 dB above the 10MB400. The higher sensitivity means the 18 Sound 10W500 produces roughly 60% more acoustic power per watt than the 10W650 at any given power level.
The 55 Hz – 4500 Hz bandwidth is 1200 Hz narrower at the top than the 10W650’s 5700 Hz. The 51 mm copper ISV coil’s higher inductance (0.72 vs 0.59 mH) and different cone-surround system produce less upper-frequency extension. For two-way systems crossing over at 2000 Hz, the 4500 Hz upper limit provides adequate overlap. For systems needing the crossover above 2000 Hz, the 10W650’s wider bandwidth provides more headroom.
18 Sound recommends a 30-litre (1.06 ft³) vented enclosure tuned to 58 Hz. The 30-litre cabinet with 58 Hz tuning is a bass-extension alignment — targeting deep, extended bass output from the ferrite 10-inch format. The 53 Hz Fs supports this deep tuning, and the 0.29 Qts keeps the bass tight and controlled at the lower frequencies where higher-Qts drivers can become boomy.
The 280 W AES / 400 W program power handling provides adequate headroom for the compact two-way and multi-way applications the 18 Sound 10W500 targets.
The comparison to the 10W650 defines a clear predecessor/successor relationship with honest trade-offs in both directions. The 10W650 improved on the 18 Sound 10W500 with SDR distortion reduction, lower inductance (0.59 vs 0.72 mH), wider bandwidth (5700 vs 4500 Hz), more enclosure flexibility (0.48 vs 0.29 Qts), and 16 Ω availability. The 18 Sound 10W500 retains advantages in sensitivity (98 vs 96 dB), force factor (14.6 vs 12.4 Tm), motor dominance (0.29 vs 0.48 Qts), bass reach (53 vs 67 Hz Fs), and deeper tuning (58 vs 70 Hz).
The 10W650 is the more versatile, lower-distortion replacement. The 18 Sound 10W500 is the higher-output, deeper-reaching original. For replacement of existing 10W500 installations, for systems where 98 dB sensitivity from a ferrite 10-inch is the specification, and for vented designs where the 0.29 Qts and 58 Hz tuning produce the tightest, deepest bass response, the 18 Sound 10W500 remains the stronger choice.
Conclusion – 18 Sound 10W500 Woofer
The 18 Sound 10W500 is the highest-sensitivity ferrite 10-inch woofer in 18 Sound’s range. The 98 dB from a copper ISV coil with 14.6 Tm Bl approaches the neodymium Tetracoil range from a ferrite platform. The 53 Hz Fs and 0.29 Qts produce tight, deep bass in vented enclosures tuned as low as 58 Hz — deeper than the 10W650 replacement achieves from its 67 Hz Fs and 0.48 Qts.
The 10W650 improved on the 18 Sound 10W500 in several areas — SDR, lower inductance, wider bandwidth, 16 Ω availability, enclosure flexibility. But it didn’t match the 18 Sound 10W500’s sensitivity or bass reach. For applications where 98 dB output and 58 Hz tuning from a proven ferrite ISV platform are the priorities, the 18 Sound 10W500 is the 10-inch woofer that proved what a copper ISV coil in a ferrite motor could deliver. Two dB louder than its replacement, 12 Hz deeper in tuning — the original that the 10W650 evolved from but didn’t fully replace.
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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.
