YAMAHA NS-690
¥ 60,000 (1 unit, around 1973)
Commentary
This 3-way bookshelf speaker system was released as a high-end model of the NS 600 series.
JA 3056, which is a 30 cm cone type unit, is used for the low range.
A composite curved cone is used for the diaphragm to keep the upper limit frequencies high, making the connection with the middle range smooth.
The voice coil uses a 66 φ bobbin made of copper ribbon wire with a high magnetic efficiency ratio and wire diameter. Insulation materials and adhesives with excellent heat resistance and heat radiation are also used. As a result, the temperature rise rate is 1.2 ℃ / W.
JA-0701, a 7.5 cm soft dome type unit, is adopted for the middle area.
The diaphragm is made of fabric with double coating of thermosetting resin and viscoelastic rubber resin, and the tangential edge is heat-molded in one piece.
It has an appropriate internal loss, does not expand near the upper limit frequency, has a back cavity, and uses a low fo to achieve a flat f-characteristic and impedance characteristic within the reproduction frequency band.
In addition, excellent directional characteristics up to 60 ° are almost the same as those of on-axis 0 °.
JA 0509, a 3.0 cm soft dome type unit, is used for the high band.
The diaphragm is made of the same material as the mid-range. It has a lightweight voice coil with aluminum ribbon wire edgewise winding, a thickness that gives the best weight balance, and a deep dome shape to increase strength.
The magnetic circuit uses a ferrite magnet with an air gap flux density of 15,500 Gauss.
An acoustic diffuser is also installed to improve directional characteristics and to protect the diaphragm.
Each unit uses an aluminum die-cast frame to prevent deterioration of sound quality due to resonance.
The network is set at 800 Hz and 6000 Hz (12dB/oct) by repeating trial listening and characteristic check, and the LC of Woofer is 5 mH and 33 μ F.
Ferrite bobbin is used for the coil to reduce DC resistance and prevent power loss, and the characteristic change due to induction is suppressed by arranging each coil at a right angle.
We also use MP capacitors with good characteristics.
The enclosure is completely enclosed, with 25 mm thick special plywood for the front baffle board and 25 mm thick particle board for the back board.
In addition, 20 mm thick plywood is used for the side plate and top plate.
The inside is reinforced with 25 mm thick plywood hollowed out to suppress resonance.
It has a castor open pore finish that makes use of the grain of the wood. On the back side, in addition to the push terminal input terminal, multi-channel terminal is mounted.
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Model Rating
| Method | 3-Way, 3-Speaker, Airtight Type, Bookshelf Type |
| Units Used | For Low Band : 30 cm Cone Type (JA-3056) For Middle Area : 7.5 cm Dome Type (JA-0701) For High Range : 3.0 cm Dome Type (JA-0509) |
| Playback frequency band | 35 Hz to 20000 Hz |
| Crossover frequency | 800 Hz, 6000 Hz (12dB/oct.) |
| Lowest resonance frequency (fo) | 40Hz |
| Impedance | 8 Ω |
| Output sound pressure level (new JIS) | 90dB/W/m |
| Maximum allowable input | 60W |
| Level control | Continuously variable type |
| External dimensions | Width 350x Height 630x Depth 312 mm |
| Weight | 22kg |