YAMAHA YST-SW1000(L)

Commentary

This is a subwoofer system that uses the Yamaha YST system to enable 16 hz ultra-low frequency reproduction.

Yamaha's proprietary YST method is adopted.
The YST (Yamaha Active Servo Technology) system consists of a negative resistance drive circuit and amplifier, a woofer unit driven with an impedance close to 0 by the amplifier, and a Helmholtz resonator (resonance box) in which the air resonance inside the port receives an ultra-low frequency by making the vibration plate of the unit part of the component.
In conventional speakers, low-frequency reproduction was restricted by the impedance rise. However, by canceling out the negative resistance circuit, the woofer unit becomes a dynamic speaker with infinite damping factor, enabling linear operation up to the ultra-low frequency range. It functions as a normal woofer with over several Hz frequency, and at the same time, the small linear vibration up to the ultra-low frequency range supplies vibration energy to the resonator. The resonator then becomes an air woofer in which the air inside the port directly vibrates by this energy, and the ultra-low frequency range is reproduced according to the resonance characteristics freely set according to the cabinet volume and the volume shape of the port. The air woofer does not have its own diaphragm, and the air inside the port itself acts as a diaphragm, so there is no distortion such as stroke distortion or magnetic distortion, and there is no difference in tone depending on the diaphragm material.


The low-frequency playback unit is equipped with a 30 cm cone woofer developed for the YST-SW1000.
This unit is made of North American spruce similar to the NS-1000M. It has been newly designed for the YST-SW1000 while taking advantage of the good quality of the material, so that the unit itself has almost flat characteristics from 70 Hz to 500 Hz. In addition, even at 30 Hz, the drop is suppressed to 10 dB. The cone shape is a straight cone type that can obtain a wide piston motor cortex range. The strength is increased by making the cone a little deep, and it is compatible with the YST-SW1000's unique air resonance in the port. In addition, the center cap made of the same material is made slightly larger, and the appropriate corrugation structure is applied, so that even though the weight is 25g, sufficient rigidity is secured.

The edge is made of a fabric with a moderate woven density and two types of resin dump material are thickly coated and impregnated. This improves the shape retention capability against large strokes and also improves the sound fading characteristics. The damper is made of a newly designed corrugated type fabric made of woven fabric impregnated with phenolic resin. By devising the shape, appropriate braking capability and linear performance for large strokes are obtained as well as accurate center retention capability.

The voice coil bobbin is made of laminated heat-resistant engineering plastic material reinforced with glass fiber. Although it has a large diameter of 52 φ x43mm, it has achieved sufficient light weight, high rigidity and high heat resistance. Moreover, the voice coil is made of OFC with excellent conductivity and edgewise winding with a high occupancy rate of 0.5x0.14 mm ribbon wire to realize a high-efficiency drive. Moreover, since it is a long voice coil with 218 mm width in contrast to the plate width of 7 mm in the gap section, the magnetostriction is minimized even in large strokes.

The magnetic circuit uses a double magnet for protection. The cancel magnet size is designed by a computer and then decided by a cut & try listening test.

Aluminum die-cast frame is used for the frame. In addition, 8 thick screws are used for fixing, indicating the vibration system firmly. In addition, the unit cover is made of 0.8 mm thick steel with circular punching to increase the opening ratio and strength. Moreover, it is covered with thin woven fabric to absorb unnecessary high frequencies and to suppress unnecessary resonance.


GT racks made of 50 mm thick high-density particleboards are used directly for the top, bottom, and side walls of the enclosure. High-density particleboards 40 mm and 30 mm thick are used for the baffle plate and the rear face, respectively, and bonded together. The front face of the connection is a fitting type, and the rear face is fixed to a fitted upper 20 mm thick reinforcement plate. In addition, it is reinforced with a large amount of 40 mm square triangular angle block for high strength and high density.
As for the internal structure, the front control part and the rear amplifier part are independent chambers made of high-density particleboards, and the lead-wire path is also sealed by rubber crimping in order to achieve airtightness and eliminate mutual influence.
In addition, the port part which is in charge of the lowest area is designed with special attention paid to materials, shape, rigidity, etc. It is wound spirally while adhering high-density pulp materials, and the surface is coated after it is made to be 7 mm thick. In addition, R is given to the Matsunochi edge by resin-based materials to increase the strength and minimize port noise.
In the YST-SW1000L, acrylic material is used for the port body and beech wood is hollowed out for the tip to increase the strength further.

It is equipped with a full-design power amplifier. This amplifier has a full-scale configuration with a discrete output stage using a high-quality 150W power transistor. The power supply section employs a three power supply system in which a ± B power supply for the main, a power supply for signal amplification and a power supply for the control system are separated, a main transformer with a large EI core, and a low-distortion large-capacity block Chemicon.
In addition, high-quality parts such as one point grounding design, high-precision custom resistance, extra-thick OFC power cable with polarity, gold-clad double-contact relay, gold-plated speaker terminal, copper earth fittings and screws, and 2 mm thick steel plate are used.

The high-frequency cutoff frequency can be continuously variable.

It has two input terminals and a volume that can be adjusted with your own speakers.

Equipped with a phase selector switch, it can be switched from normal positive-phase connection to negative-phase connection according to preference.

It comes with a remote control that allows you to make various fine adjustments while you are in the listening position, including high cutoff frequency and level.

In addition to the YST-SW1000 with birch makeup black paint finish, there was also the YST-SW1000L with walnut makeup urethane paint finish as a made-to-order product.
The material of the port is different between YST-SW1000 and YST-SW1000L.

Model Rating

Method	Built-in Power Amplifier / 1-Way / 1-Speaker / YST System ・ Floor type ・ Magnetic protection design
Units Used	For low band : 30 cm cone type
Woofer Port Diameter	9.0cm
Playback frequency band	16 Hz to 160 Hz (-10dB)
Lowest resonance frequency	30Hz
Input impedance	SP input : 4.7k Ω Line input : 10k Ω
Amplifier output	120W (5 Ω, Strain 0.01%)
Cutoff frequency	30 Hz ~ 130 Hz Continuously Variable (-24dB/oct.)
Power consumption	100W
External dimensions	Width 580x Height 440x Depth 440 mm
Weight	48kg
Attachment	Remote control Speaker cord (4mx2)