Technics SB-3A

Commentary

A 2-way speaker system using a honeycomb flat diaphragm.

Each speaker unit uses a honeycomb flat diaphragm that is light and highly rigid.
This diaphragm has a planar structure using an aluminum alloy-made honeycomb structure in order to obtain accurate piston motion while eliminating air resonance (front chamber effect) generated in the cavity in front of the cone of a cone-type speaker. Rigidity is 1,000 to 1500 times that of a paper cone. There is no distortion due to deformation caused by Dainyu force, or characteristic degradation due to aging or temperature change.
In addition, in order to solve the problem that a part that does not move at all (= node) at a specific frequency occurs when the center of the flat diaphragm is driven, we have adopted a node drive that drives by connecting a voice coil to the node. In addition, in order to cope with the problem that the appearance of nodes differs depending on the shape and frequency of the diaphragm, we have developed a unique axisymmetric honeycomb that increases the density of the honeycomb toward the center. By eliminating the difference in strength between the left and right sides, the node is made into a perfect circle, and node drive with one circular voice coil is possible.

A 22 cm honeycomb planar woofer is installed in the low range.
This unit uses a large magnet with a diameter of 120 mm and weight of 640g, which is comparable to the conventional 25 cm class, and realizes high efficiency. In addition, a large voice coil with a diameter of 32 mm is used for the voice coil, and a laminated polyimide resin film with little deformation even at high temperatures is used for the voice coil bobbin, thereby realizing high input resistance that can withstand high temperatures of 250 ℃.
Rolling (fluctuation) resistant moltoprene edge is used for the edge to improve the linearity during Dainyu force.

A 2.8 cm honeycomb plane type tweeter is mounted in the high range.
The magnetic circuit of the tweeter uses a magnet with a magnetic flux density of 17,500 gauss. In addition to the large magnet, the pole piece is made into a conical shape to prevent time saturation. This is an original contrivance to improve efficiency.
In addition, a special shape equalizer is installed on the front of the tweeter to make the frequency characteristics flatter and improve efficiency.
In addition, the gap between the voice coil, pole piece, and yoke (magnetic gap) is filled with magnetic fluid, and heat generated by the voice coil is released through the magnetic fluid to the pole piece or other material with a large heat capacity to improve heat radiation effect.

In order to demonstrate the performance of the honeycomb planar unit, the network employs elements that have been carefully examined in terms of performance and reliability. The core of the choke coil employs a ferrite core with low loss and low distortion. The arrangement of components is also taken into consideration to minimize crosstalk between units.
In addition, the tweeter is equipped with a thermal relay protection circuit to prevent unit breakage due to excessive input or abnormal signal. This protection circuit can be restored with one touch by pressing the reset button on the rear panel.

The enclosure uses a bass reflex system. The bass reflex port uses a specially shaped port that is integrally molded to prevent standing waves in the enclosure. The inner surface is smooth to reduce friction loss when air moves inside the port.
In addition, the baffle plate is 18 mm thick and the other parts are 15 mm thick rigid particle board. In addition, the vibration analysis by the finite element method with the introduction of a computer provides effective reinforcement to reduce unnecessary vibration. In addition, the wooden frame is equipped with a three way Z-stop by advanced woodworking technology to prevent distortion due to aging.

Model Rating

Method	2-Way, 2-Speaker, Bass Reflex System, Bookshelf Type
Unit	For Low Band : 22 cm Flat Type For High Frequency : 2.8 cm Flat Type
Frequency characteristic	55 Hz to 35 kHz -10dB
Output sound pressure level	92dB/W/m
Impedance	8 Ω
Allowable input	90W(Music) 60W(Din)
Crossover frequency	2kHz
External dimensions	Width 270x Height 440x Depth 238 mm
Weight	8.5kg