YAMAHA NS-690III

Commentary

Based on the NS 690 II, this is a speaker system that is more complete with sprue scone and other technologies.

A 30 cm cone type woofer JA 3060 a is mounted in the low range.
The diaphragm is made of spruce for the soundboard of a grand piano, and also of a single tree of which the grain is especially simple. It is finished by Yamaha's original technology from beating to cutting and pressing. The diaphragm is finished in a conical type with corrugation to reduce split vibration and obtain a wide range of piston motion.
In addition, a foamed urethane roll edge is used for the edge, and the damper supporting the vibration system is also made of materials and impregnation materials with sufficient consideration.
The voice coil is a long voice coil type in which a Cu ribbon wire is edgewise wound on a Nomex bobbin with excellent heat resistance. The voice coil does not deviate from the magnetic field even when the Dainyu force is applied, and operation with good linearity is ensured.
The magnetic circuit uses a ferrite magnet of 156 φ -80 φ -20t with a magnetic flux density of 10,000 gauss and a total magnetic flux of 200,000 maxwell. In addition, the center pole is covered with a copper cap to reduce the generation of magnetic strain, thereby suppressing the 3rd harmonic component that is annoying.

In the middle area, it is equipped with 7.5 cm soft dome type skoka JA 0701 c.
The diaphragm is based on a woven fabric with the same density of the warp and the cross plate to reduce directivity and dispersion. It is coated with a newly developed multi-coating agent that blends several kinds of viscoelastic chemicals. It is molded in one piece including tangential edges.
The voice coil is made of Yamaha's original FRP sheet made of glass fiber and wound with copper flat wire with high space factor to achieve high input resistance. The bobbin has several air holes to equalize the air pressure inside and outside the bobbin, thereby achieving high transient, smooth and linear operation.
The magnetic circuit uses a ferrite magnet of 120 φ -60 φ -22t with a magnetic flux density of 14,500 gauss and a total magnetic flux of 72,000 maxwell. The glass wool filled inside the unit and the air brake by the back cavity are combined to realize fo300Hz.
It is a wide-band unit with characteristics of 300 Hz to 15 kHz, but it uses 800 Hz to 6 kHz with especially low distortion rate.

A 3 cm dome type tweeter, JA-0509C, which uses a soft dome diaphragm of integrally molded edge as well as the middle band, is installed in the high band.
The basic structure of the diaphragm is the same as that of the mid-range diaphragm. However, due to its small diameter, it is thinner and lighter in consideration of the weight balance with the voice coil and in order to extend the high-range characteristics. In addition, in order to improve the directional characteristics, the dome shape is made deeper than usual.
The voice coil is made of a lightweight and highly conductive pure aluminum ribbon wire with edgewise winding, and is directly connected to the soft dome diaphragm to realize weight reduction of the vibration system as a whole.
The magnetic circuit uses a ferrite magnet of 80 φ -40 φ -20t in size with a magnetic flux density of 15,500 gauss and a total magnetic flux of 22,000 maxwell.
In addition, air holes are made in the outer pole on the back side of the edge as well as in the middle area to let air escape from the edge to smooth the movement of the edge. In addition, an acoustic diffuser is installed on the front of the diaphragm to improve the directional characteristics and frequency characteristics that cause problems in high frequencies.

The frame of each unit is made of die-cast aluminum utilizing Yamaha's alloy technology, providing strong support for the vibration system.

The Network Division is designed as a whole with a focus on smooth connections in the middle and low bands and enhancement in the middle and high bands.
High-purity copper wire with low DC resistance is used for the bobbin made of large ferrite core for the coil, and MP capacitor selected by audibility test is used for the capacitor.
In addition, in order to reduce the effect of mutual inductance between coils, they are installed at right angles to each other while keeping a sufficient distance.

It is equipped with a level control that can be adjusted to + 2 db ~ ∞ for the middle range and + 3 db ~ ∞ for the high range.

The enclosure has a completely enclosed structure and is made of high-density particleboards that have been selected through hearing tests.
The baffle plate and back plate are 25 mm thick, and the side plate and top plate are 20 mm thick. On the back side, a Woofer cut disk is bonded for reinforcement. In addition, it is reinforced by utilizing the woodworking technology obtained through the creation of the musical instrument, so that resonance is eliminated.
Two carefully selected types of sound absorbing materials are used.
It is finished with American Walnut real makeup with an open pore finish.

Model Rating

Method	3-Way, 3-Speaker, Airtight Type, Bookshelf Type
Units Used	For low band : 30 cm cone type For Middle Area : 7.5 cm Dome Type For high-pass : 3.0 cm dome type
Playback frequency band	35 Hz to 20000 Hz
Lowest resonance frequency	40Hz
Maximum allowable input	80W
Rated input	40W
Output sound pressure level	90dB/W/m
Impedance	8 Ω
Crossover frequency	800 Hz, 6 kHz (12dB/oct.)
Internal volume	44L
External dimensions	Width 358x Height 630x Depth 315 mm
Weight	27kg