KENWOOD LS-990A
¥ 59,800 (1 unit, around 1985)
Commentary
This speaker system incorporates Class A suspension and other technologies to accommodate the wide dynamic range of digital sources.
The Class A suspension is a technology unique to Kenwood. It uses two suspensions molded from engineering plastic polyamide fiber. It has an appropriate mechanical bias even when it is stationary. As the voice coil vibrates, it repeats a push-pull operation in which one expands and the other contracts.
This push-pull operation cancels out the mutually opposite nonlinear distortion components, and realizes linear motion of the vibration plate that can be converted into small amplitude for small signals and large amplitude for large signals.
A 33 cm cone woofer is used for the low range.
It has a 3-layer structure with a hard resin layer sandwiched between pulp layers reinforced with HR carbon and ribs, and at the same time, it has high rigidity and suppresses the natural squeal of the material.
A large magnet with a total flux of 88000 maxwell and a four layer voice coil are used for the drive system.
A 10 cm semi-dome type squaker is used for the middle area.
The dome part is ion-plated in the same way as the tweeter to obtain high rigidity, suppress the noise inherent in metal, and adopts ion-plated titanium dome directly connected to the voice coil bobbin.
In addition, we have introduced technologies to enhance sound quality, such as a specially treated lightweight cone for the cone section, a 61000 maxwell magnet for the magnetic circuit, thermosetting adhesive aluminum wire for the voice coil, and aluminum die-cast with reinforcing ribs for the frame.
A 2.5 cm hard dome type tweeter is used for the high range.
The vibrating plate has been developed by introducing ion plating technology. Titanium nitride is ionized and accelerated in a plasma state to be deposited on the surface of titanium. Since the kinetic energy of the molecules of titanium nitride is increased for the deposition, the vibrating plate has high deposition strength and hardness more than six times that of highly rigid titanium.
The voice coil uses a lightweight aluminum wire and the magnetic circuit uses a strontium ferrite magnet to achieve a total magnetic flux of 24000 maxwell.
The network uses dedicated printed circuit boards for the woofer, squaker, and tweeter, and is arranged separately so that crosstalk due to magnetic flux leakage and crosstalk due to ground lines are suppressed.
Oxygen-free copper is used for the wire material and coil winding.
The cabinet consists of side and back boards made of 20mm-thick coniferous high-density particleboards, and the strength of the front baffle is especially emphasized with a structure consisting of 18mm-thick and 12mm-thick particleboards bonded together to improve the strength.
In addition, consideration has been given to bending the duct so that the sound inside the cabinet does not escape directly to the front, and setting the port to be short.
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Model Rating
| Method | 3-Way, 3-Speaker, Bass reflex system, Bookshelf Type |
| Unit | For low band : 33 cm cone type For Middle Area : 10 cm Semi-dome Type For high-pass : 2.5 cm dome type |
| Playback frequency band | 28 Hz to 45 kHz |
| Max Input | 190W |
| Impedance | 6 Ω |
| Output sound pressure level | 92dB/W/m |
| Crossover frequency | 600 Hz, 5 kHz |
| External dimensions | Width 355x Height 671x Depth 321 mm |
| Weight | 22kg |