18 Sound 15MB700 – Exceptional-Efficiency Ferrite 15-Inch Mid-Bass with 103 dB Sensitivity
The 18 Sound 15MB700 very high output mid-bass transducer shows exceptional efficiency and is primarily intended for two-way very compact reflex systems (75 litres), three-way systems, and horn-loaded applications. It combines high sensitivity (103 dB 1W/1m) with a high power handling capability — this is the highest sensitivity documented across this entire 15-inch session, matching the neodymium 15NMB1000’s 101 dB by 2 dB more, and notably the same driver the neodymium 15NMB420 pointed to as its own current alternative earlier in this session.
The 75 mm diameter aluminium voice coil features the same technology fitted to 18 Sound’s top-of-the-range 4-inch voice coil models. It employs Interleaved Sandwich Voice Coil (ISV) technology, in which a high-strength fibreglass former carries windings on both the outer and inner surfaces to achieve a mass-balanced coil. This results in an extremely linear motor assembly with reduced tendency for eccentric behaviour when driven hard. The low coil inductance results in an improved transient response.
The smooth textured curvilinear paper cone, in conjunction with the viscose dampened multiroll suspension, provides excellent cone dampening and excursion control. Due to the increasing use of audio systems at outdoor events, the ability to perform in adverse weather conditions or in high-humidity areas is a key feature of the 18 Sound 15MB700.
At 8.3 kg with 400 W AES power handling, the 18 Sound 15MB700 proves that ferrite construction can match or exceed neodymium sensitivity figures documented elsewhere in this session — the same efficiency-over-neodymium pattern documented on the ferrite 12MB720/710 pairing much earlier. 18 Sound now lists the 15MB1000 as the alternative/current model.
Design and Construction of the 18 Sound 15MB700
The 75 mm diameter aluminium voice coil features the same technology fitted to 18 Sound’s top-of-the-range 4-inch voice coil models. It employs Interleaved Sandwich Voice Coil (ISV) technology, in which a high-strength fibreglass former carries windings on both the outer and inner surfaces to achieve a mass-balanced coil. This results in an extremely linear motor assembly with a reduced tendency for eccentric behaviour when driven hard. The low coil inductance results in an improved transient response — the 1.2 mH Le is genuinely well-controlled for a ferrite 75 mm coil without SDR or DDR ring assistance.
Excellent heat dissipation has been achieved by incorporating air channels into the basket design, between the basket and the top plate. Maximum flux concentration and force factor in the gap are assured by the unique shape and design of the top and back plates, which have been designed using 18 Sound’s in-house Magnetic Flux FEA CAD resource.
The 17.6 Tm force factor driving just 73 g of moving mass — the lightest moving mass of any ferrite 15-inch driver documented across this session — produces the driver’s exceptional 103 dB sensitivity and 0.29 Qts / 135 Hz EBP alignment. The Bl/Mms ratio of 0.241 Tm/g is competitive despite the modest force factor, confirming that the featherweight moving assembly is doing much of the sensitivity work here rather than sheer motor force alone.
The smooth textured curvilinear paper cone, in conjunction with the viscose dampened multiroll suspension, provides excellent cone dampening and excursion control through the 5.5 mm Xmax — a design specifically optimised for high sensitivity and controlled mid-bass output rather than maximum displacement.
Due to the increasing use of audio systems at outdoor events, the ability to perform in adverse weather conditions or in high-humidity areas is a key feature of the 18 Sound 15MB700. This has been achieved using exclusive cone and magnetic plate treatment processes which allow the speaker to resist corrosion and render the cone water repellent.
At 8.3 kg, 387 mm overall diameter, 353 mm baffle cutout, 167 mm depth, and 19 mm flange, the 18 Sound 15MB700 carries the substantial ferrite motor mass necessary to achieve its exceptional sensitivity figure.
Performance and Applications for the 18 Sound 15MB700
The 18 Sound 15MB700 delivers 103 dB sensitivity across a 45 Hz – 4300 Hz bandwidth — the highest sensitivity of any 15-inch driver documented across this entire session, 2 dB above the neodymium 15NMB1000’s 101 dB and 4 dB above the neodymium 15NMB420’s 99 dB. This is a genuinely remarkable outcome from a ferrite motor.
18 Sound recommends a 90-litre (3.18 ft³) vented enclosure tuned to 45 Hz. The driver is primarily intended for two-way very compact reflex systems at 75 litres, three-way systems, and horn-loaded applications, suitable for compact two-way, multiway, and horn-loaded mid-bass applications.
The 400 W AES / 600 W continuous program power handling, combined with the driver’s exceptional 103 dB sensitivity, produces very high maximum sustained output — the same acoustic power output that a lower-sensitivity driver would require substantially more amplifier power to achieve.
The excellent transient response 18 Sound highlights is a direct consequence of the low coil inductance combined with the lightweight 73 g moving assembly — the driver responds quickly and cleanly to complex musical transients, an important characteristic for mid-bass applications where articulation and definition matter alongside raw output.
For horn-loaded mid-bass applications specifically, the 103 dB sensitivity combined with the 0.29 Qts and 135 Hz EBP produces exceptional SPL from the horn-loaded configuration — few 15-inch drivers from any manufacturer, ferrite or neodymium, approach this combination of sensitivity and motor control.
The comparison to the neodymium 15NMB420 (which lists the 18 Sound 15MB700 as its own alternative) shows the two drivers occupy genuinely complementary positions: the 15NMB420 delivers lighter weight (3.9 vs 8.3 kg) at 99 dB; the 18 Sound 15MB700 delivers 4 dB more sensitivity from the heavier ferrite platform. For weight-critical applications, the neodymium option wins decisively; for maximum sensitivity where weight is a secondary consideration, the 18 Sound 15MB700 is the stronger specification.
Conclusion – 18 Sound 15MB700 Mid-Bass Driver
The 18 Sound 15MB700 delivers the highest sensitivity of any 15-inch driver documented across this entire session — 103 dB from a ferrite motor with a 75 mm ISV coil sharing technology with 18 Sound’s top-of-the-range 4-inch voice coil models. The viscose dampened multiroll suspension, low coil inductance, and lightweight 73 g moving assembly combine for excellent transient response alongside the driver’s exceptional efficiency.
For two-way very compact reflex systems, three-way systems, and horn-loaded mid-bass applications where maximum sensitivity defines the specification — and where the 8.3 kg ferrite weight is an acceptable trade-off against the lighter neodymium 15NMB420 alternative — the 18 Sound 15MB700 remains one of the most efficient 15-inch mid-bass drivers 18 Sound has ever produced.
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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.
