At 27kg, it doesn’t just sit on your stand—it stakes a claim, promising bass that starts where most bookshelf speakers give up.

Overview

The Yamaha NS-690 II isn’t a speaker for the faint of heart or the underpowered amplifier. At 27 kilograms, it’s a dense, no-nonsense block of engineered intent—bookshelf in name only, given its 630mm height and sealed cabinet demanding space and respect. , it was Yamaha’s answer to the growing demand for high-fidelity systems that could deliver deep, controlled bass without venting to the outside world. This is a 3-way, airtight (sealed) bookshelf system, but “bookshelf” here is almost a misnomer; these are stand-mount speakers in the grand Japanese tradition of the late 1970s—overbuilt, over-specified, and acoustically ambitious.

Its lineage is clear: the NS-690 II exists to refine the NS-690, pushing further toward sonic neutrality and structural integrity. It sits between the NS-690 and NS-690 III in the product family, but it’s the engineering details that reveal its true ambition. The low-end driver, the JA-3060, is a 30 cm cone woofer that borrows heavily from the legendary NS-1000M—same size, same basic construction, same 156 φ ferrite magnet. But Yamaha made a deliberate choice: replacing the cloth surround with urethane foam, a move that altered the damping characteristics and, reportedly, softened the transient edge just enough to suit a wider range of listening environments. Whether that was a step toward warmth or a compromise in longevity is still debated, but the decision signals intent—this wasn’t just a cut-down NS-1000M. It was a recalibration.

The sealed enclosure is a critical part of that story. With a lowest resonance frequency of 40 Hz and a frequency response extending down to 35 Hz, the NS-690 II achieves deep bass without a port, avoiding the time-smearing and chuffing that can plague reflex designs. That’s no small feat for a speaker of this size, and it speaks to the quality of the suspension and motor system. The cabinet itself is serious business: front and back panels are 25 mm thick, sides and top 20 mm, using particleboard with 10% higher density than the previous model. The back panel is now glued rather than screwed, improving long-term seal integrity—critical in a system where internal air pressure is part of the suspension design.

Sensitivity is a healthy 90 dB/W/m, and with an 8 Ω nominal impedance, it’s not especially difficult to drive—on paper. But that 35 Hz lower limit demands amplifier control, and the 80W maximum input suggests Yamaha expected these to be paired with robust receivers or separates. The crossover, set at 800 Hz and 6 kHz with a 12 dB/octave slope, is a passive 3-way network using MP capacitors and ferrite-cored coils mounted at right angles to minimize interference. It’s not exotic by modern standards, but the attention to layout and component selection reflects a philosophy of measured, repeatable performance.

Owners report that the real magic lies in the mid and high drivers. The 7.5 cm JA-0701B soft dome squawker uses a double-coated diaphragm with a proprietary mixed coating agent—same as the 3 cm JA-0509B tweeter. Both drivers feature integrally molded tangential edges and aluminum die-cast frames, contributing to rigidity and reduced resonance. The tweeter’s 15,500 gauss flux density and edgewise-wound aluminum ribbon voice coil suggest an effort to minimize mass and inductance, aiming for speed and clarity. And with continuously variable level controls for both mid and high ranges, the NS-690 II offers rare flexibility for tonal tailoring—a feature that hints at Yamaha’s awareness of room and system variability.

Some describe the sound as “transparent but pleasing,” a balance between analytical precision and listenability. It doesn’t scream “monitor” like the NS-1000M, but it doesn’t retreat into euphonic flattery either. It’s a speaker that wants to be truthful, but not cruel.

Specifications

Key Features

30 cm Cone Woofer with Urethane Foam Edge (JA-3060)

The heart of the NS-690 II’s low-end performance is the JA-3060, a 30 cm cone woofer that shares its core structure and materials with the flagship NS-1000M. The most significant deviation is the substitution of the cloth surround with urethane foam—a decision that likely improved production consistency and reduced cost, but also altered the long-term reliability. Urethane foam edges are notorious for drying out and crumbling over decades, a known failure point in many vintage speakers. However, at the time, the foam offered a more predictable damping profile and tighter manufacturing tolerances. The cone itself uses Yamaha’s proprietary paper formulation, finished in a corrugated conical shape for stiffness, while the voice coil is wound from copper ribbon on a Nomex bobbin—lightweight, thermally robust, and resistant to deformation. A 156 φ ferrite magnet and copper center cap help control inductance and improve transient response, making this a driver built for authority and extension, not just volume.

Double-Coated Soft Dome Midrange (JA-0701B)

The 7.5 cm JA-0701B soft dome squawker is engineered for low distortion and high linearity. Its diaphragm uses a double-coated material with a new mixed coating agent—presumably a blend designed to balance stiffness and damping. The integrally molded tangential edge eliminates adhesives that could introduce non-linearities, while the FRP (fiberglass-reinforced plastic) bobbin provides rigidity without excess mass. Air holes in the bobbin aid cooling, and glass wool inside the rear chamber contributes to internal damping. With a Q of 0.5 and a free-air resonance of 280 Hz, the unit is well-matched to the crossover point at 800 Hz, operating well above its resonance for optimal control. The 120 φ ferrite magnet delivers a strong 14,500 gauss flux density in the gap, ensuring high motor strength and dynamic capability.

3 cm Soft Dome Tweeter with Edgewise-Wound Voice Coil (JA-0509B)

The JA-0509B tweeter is a study in minimizing moving mass. Its 3 cm soft dome uses the same double-coated diaphragm technology as the midrange, ensuring tonal continuity. The edge is integrally molded, reducing breakup modes, and the voice coil is wound edgewise from lightweight aluminum ribbon wire—maximizing surface area for cooling while minimizing inductance. The magnetic circuit, a 80 φ ferrite magnet, generates a high 15,500 gauss flux density, contributing to excellent transient response. An air hole in the outer pole piece behind the edge helps equalize pressure and reduce diaphragm rocking. This is not a tweeter designed for brightness or etch; it’s built for speed, clarity, and fatigue-free listening.

Hermetically Sealed Cabinet with Reinforced Particleboard

The NS-690 II’s sealed enclosure is fundamental to its bass performance. Unlike ported designs, it avoids port noise and group delay, relying instead on the compliance of the air inside the cabinet to act as part of the suspension system. The cabinet uses particleboard with 10% higher density than the NS-690, enhancing rigidity and reducing panel resonance. The front and back panels are 25 mm thick—substantial for the era—and the woofer cutout in the baffle is bonded to the back plate as a structural reinforcement. The back panel is sealed with adhesive rather than screws, a change from the previous model that improves long-term airtightness. Any leak in this system would compromise the bass response, making cabinet integrity non-negotiable.

Continuously Variable Mid and High Frequency Level Controls

Few speakers of this era offered such precise tonal adjustment. The NS-690 II includes continuously variable level controls for both the midrange and high-frequency drivers, allowing users to tailor the sound to room acoustics or personal preference. This isn’t a simple bass/treble cut; it’s driver-level attenuation, giving real control over balance. In a system where the midrange and tweeter are so carefully engineered, the ability to fine-tune their output is a significant advantage—especially in rooms with reflective surfaces or unusual dimensions.

Historical Context

The NS-690 II was developed as a refinement of the NS-690, aiming to enhance sonic perfection through improved materials and construction. It occupies a middle position in the NS-690 series, sitting between the original NS-690 and the later NS-690 III. This incremental development reflects Yamaha’s methodical approach to speaker design in the late 1970s—evolutionary, not revolutionary. The use of drivers derived from the NS-1000M signals Yamaha’s intent to trickle down flagship technology, but with adjustments (like the foam surround) that suggest a balance between performance, cost, and manufacturability.

Collectibility & Value

The most commonly reported issue with vintage Yamaha speakers like the NS-690 II is degraded foam surrounds. Over time, the urethane edges on the woofer and potentially the midrange can dry out, crack, or disintegrate, requiring refoaming—a common but necessary restoration step. One repair technician reportedly quoted around $120 for such work, though prices vary. Market values are inconsistent: one source suggests a pair in need of foam replacement might sell for $250–$300, while another estimates average used prices between $350 and $500, with higher figures for mint examples. A Facebook listing once asked “70k” for a pair, though currency and condition were unspecified. Given the lack of comprehensive pricing data, current value appears highly dependent on condition, restoration status, and regional market demand.

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