Technics SB-M1 Monitor-1

Commentary

As the first monitor speaker of Technics, this is a 4-way floor type speaker system developed based on the concept of high fidelity reproduction of original sound.

Most of the 25 Hz-38 kHz band is used for piston motion reproduction. For music reproduction, a flat frequency characteristic of ± 1.5 dB is obtained in the 150 Hz-15 kHz band, which determines the tone of the instrument. In addition, the distortion factor of the main band at 1W input power is -55dB or less.

In a typical cone type speaker, a phenomenon called the "cavity effect" occurs. Since there is always a time difference between the sound reproduced from the center part of the diaphragm and the sound reproduced from the different part, the frequency characteristic is disturbed by the resonance of air.
In order to solve this problem, Technics has adopted a honeycomb disk flat diaphragm to obtain flatter frequency characteristics.

In order to obtain sound with excellent linearity against air resistance with a flat diaphragm, we have adopted a honeycomb structure made of aluminum alloys. This is a lightweight, high-rigidity honeycomb structure used in some jet planes and space ships. It is 1,000 to 1,500 times more rigid than paper cones. There is almost no distortion due to deformation caused by Dainyu force, or characteristic degradation due to aging or temperature change.

In order to expand and flatten the frequency characteristics by taking advantage of the honeycomb structure adopted for this flat diaphragm, the piston motion band is expanded by the nodal drive structure.
The flat diaphragm has a feature that when it is vibrated in free space, a part (node) which does not move at all at a specific frequency appears. The resonance mode is canceled by the principle of node drive which drives by connecting a voice coil to this node part, and it becomes possible to expand the piston motion range to a higher vibration mode.
In addition, the SB-M1 uses a circular diaphragm because the simpler the pattern of node appearance, the more ideal node drive becomes possible.
Furthermore, in the honeycomb structure with hexagonal cells, the strength is directional due to the structure of the core, and the resonance node appears to be elliptic, making it difficult to accurately drive the node with a circular voice coil. To solve this problem, we have adopted an axisymmetric honeycomb core. This not only makes the node circular, but also solves the problem that resonance occurs at a common frequency because each hexagonal cell has the same size. Furthermore, the node can be made smaller than that of an ordinary honeycomb core, and the configuration of the voice coil is also advantageous.

A 38 cm honeycomb planar woofer is mounted in the low range, and by driving the honeycomb diaphragm, piston motion of 2 khz or more is possible.
The SB-M1 woofer uses a newly developed linear damper with a special structure to enhance linearity in particular. This damper has vertically symmetrical gathers arranged in four directions. It is more than 10 times more resistant to inclination than a normal damper. Therefore, rolling can be minimized and excellent linearity is obtained even during Dainyu force.
The magnetic circuit uses a large and strong magnet with a diameter of 200 mm, weight of 3.2 kg, magnetic flux density of 14,800 gauss and total magnetic flux of 500,000 maxwell to realize high efficiency of 94dB/W. The voice coil bobbin uses a laminated film of polyimide resin and is designed to withstand high temperatures of 250 ° C.
The SB-M1 is designed to allow room to use this unit by crossing over at 280 Hz.

A 22 cm honeycomb flat type mid-low unit is mounted in the middle and low range, and piston motion up to 4 khz is realized by nodal drive.
In order to achieve high efficiency, this unit uses a 156 mm direct magnet with a weight of 1.4 kg, a total magnetic flux density of 11,000 gauss and a total magnetic flux density of 270,000 maxwell. In addition, a voice coil with a diameter of 60 mm is designed for high input resistance.
This unit can be used with a crossover of 900 Hz to allow sufficient margin.

An 8 cm honeycomb flat type mid-high unit is mounted in the middle and high range. By directly driving the node of the diaphragm with a voice coil of 50 mm diameter, piston motion reproduction capability of up to 10 kHz is obtained.
The magnetic circuit uses a strontium magnet with a diameter of 140 mm and a weight of 1.2 kg. Combined with a lightweight and highly rigid diaphragm, achieves a high efficiency of 94dB/W.
In addition, peaks and dips are suppressed by controlling the cavity composed of the edge part and the edge cover.

A 2.8 cm honeycomb plane type tweeter is mounted in the high range.
The honeycomb core of this unit differs from that of other units in the shape of the core. It has an aluminum alloy ribbon of 1 mm wide and 20 μ m thick in the floriform shape of chrysanthemum, and uses laminated mica for the skin material of the core. Mica particles are hardened with epoxy resin. The speed of sound is as fast as 6700m, the specific gravity is as light as 1.9, the Young's modulus is high, and the bending rigidity is about three times that of aluminum.
In addition, a 800g weight strontium magnet is used for the magnetic circuit, and the space between the mid-high and the tweeter is narrowed and the shape is rectangular to improve the directional characteristics in the vertical direction.
In addition, the space between the voice coil and the magnetic pole is filled with a magnetic fluid to release heat to the pole piece and yoke, thereby the heat radiation effect and improving input resistance.

The network section uses a large-size, low-strain choke coil for woofer, ferrite core for low strain, and metalized polyester film capacitor with superior high-frequency characteristics for higher performance and reliability.
We have also introduced computers into the network design to improve the design accuracy of the entire system.

A thermal relay protection circuit is mounted to prevent damage to the tweeter caused by excessive input or abnormal signal.
It also has a reset button.

The tweeter, mid-high and mid-low are equipped with independent attenuators.

It is equipped with a terminal terminal that can handle very thick speaker cords.

The enclosure has an internal volume of 170L and is a bass-reflex structure. The material is 30 mm thick high-density particle board, and the total weight reaches approximately 93 kg by SB-M1 (M).
Mid-high and mid-low have independent back cavities to prevent interference from the woofer, and the shape of the back cavity uses a special shape to prevent standing waves.
In addition, the bass reflex port has a shape with reinforcing material in consideration of standing wave.

A symmetrical design is adopted.
The attenuator plate is designed to be flat with the baffle plate so that the position where the attenuator is inside is the correct position, thus improving the directional characteristics at the listening position between the speakers.

The exterior of SB-M1 (M) is lavishly made of natural wood. Carefully selected rosewood is hand-made one by one by experts who have more than 30 years of experience in building enclosures.
In addition, Rosewood muku is used for the interior wall of the bass reflex port and the frame wood of the sub RUNNET for a gorgeous finish.

SB-M1 (S) has a gray paint as a monitor like design.

Model Rating

Method	4-Way, 4-Speaker, Bass Reflex System, Floor Type
Unit	For Low Band : 38 cm Flat Type For Middle and Low Band : 22 cm Flat Type For Middle and High Areas : 8 cm Flat Type For High Frequency : 2.8 cm Flat Type
Frequency characteristic	25 hz to 38 khz -16dB 35 Hz to 35 kHz -10dB
Output sound pressure level	94dB/W/m
Impedance	6 Ω
Allowable input	350W(Music) 150W(Din)
Crossover frequency	280 Hz, 900 Hz, 4 khz
External dimensions	SB-M1 (M) : 630 mm wide x 1,120 mm high x 439 mm deep SB-M1 (S) : 630 mm wide x 1,050 mm high x 439 mm deep
Weight (net included)	SB-M1(M):92.5kg SB-M1(S):85.5kg