Audio Database

DS-28B Image
Commentary

A speaker system developed to realize dynamic and high-presence playback.

A 25 cm cone type woofer, PW 2521 bma, is mounted in the low range.
The cone paper of this unit is composed of a mixture of three kinds of pulp and moderately beaten Japanese paper with excellent physical properties placed as a key point. It realizes a diaphragm for sealed use with both airtightness and moderate loss.
In addition, the U-shaped edge with excellent dynamic linearity is used for the edge. The neutral position of this edge is slightly shifted in the stationary state so that the neutral position can be kept well in the operating state. In addition, the newly developed material is used. Various aspects such as the study of the physical properties of the fiber itself, the thickness of the fiber for a non-directional weave, and the ratio of warp and weft are examined. The surface of the edge is coated with a mixture of thermosetting resin and viscoelastic resin in several times, and a special damping treatment is applied at the final finish to ensure smooth movement.
The magnetic circuit uses an expensive Alnico cast magnet to reduce distortion and stabilize dynamic characteristics. In addition, the magnet material uses MK magnet (made by Mitsubishi Steel) with large BH product developed for high-grade speakers.
A 4 mm thick aluminum die-cast frame is used for the frame to reduce the natural vibration of the frame and unnecessary sound emission from the frame itself.

The mid-range is equipped with PM-1021CM which is a 10 cm cone type squaker.
A catenary curved cone is used for the cone. The cone section of this cone follows the catenary curve. When the cone paper is panned from pulp, it is panned in a very natural manner so that no strain occurs inside the fiber. In addition, since the stress vector generated inside the cone from the voice coil to the edge direction follows a natural form, no abnormal or natural vibration occurs, and smooth characteristics and stable physical properties are obtained. In addition, by adopting a matched resonant type with corrugation, a wide range of directional characteristics and cone strength are obtained.
In addition, the center cap is subjected to a damping treatment to suppress the natural vibration of the cap itself by analyzing the vibration mode using laser holography, thereby suppressing the radiation of strain sound from the center cap and adverse effects on the vibration of the cone paper.
V-shaped Cross Edge is used for the edge part. This edge is V-shaped considering that it has excellent linearity within the practical range of amplitude and is strong against lateral vibration. Thick fiber is used for the material to realize the edge with high stiffness. In addition, by coating damping and quantity on this V-shaped Cross Edge, airtightness is increased and linearity is further improved. This V-shaped Cross Edge greatly improves linearity at small amplitude.
This unit is equipped with a fully enclosed back chamber in the rear part of the diaphragm. By using an acoustic load type in which sound absorbing material is filled in the air quality, interference with the woofer is suppressed and intermodulation distortion is reduced.

A 3 cm dome type tweeter, DH-2203CMA, is mounted in the high range.
A polyester resin diaphragm is used for the diaphragm. This material was determined by vibration analysis of the diaphragm using laser holography. Since it has appropriate rigidity and internal loss, it has high efficiency and smooth characteristics.
In addition, in order to prevent performance degradation due to rolling phenomenon and aging, a very narrow straight edge is adopted at the edge. This straight edge is supported by a unique sandwich structure and fixed via an elastic body, thereby eliminating abnormal resonance and unnecessary sound at the edge.

The network section uses a soft displacement type coil with no change in sound quality from low level to high level and good sound expansion even with large input.
In addition to improving sound transparency, we have adopted a bipolar capacitor that uses plain foils, which are highly reliable even under the influence of Dainyu.

Level control is provided for the middle and high frequencies.

The enclosure is hermetically sealed and has a unique distributed resonant structure.
In the distributed resonance enclosure, the vibration pattern of the cabinet is physically analyzed and the reinforcement elements are unevenly distributed. No simple joining methods are used in the cabinet joint structure, and all joints are made with a strong structure requiring advanced woodworking techniques. This disperses the resonance modes and prevents the cabinet from resonating too much in a certain bandwidth.
The cabinet is made of high-density multi-layer particleboards with excellent acoustic characteristics.

The front baffle has an edge-less structure.
Instead of the recessed front baffle used in conventional speakers, the edge around the baffle plate has been removed to improve directional characteristics.

Model Rating
Method 3-Way, 3-Speaker, Airtight Type, Bookshelf Type
Units Used For Low Band : 25 cm Cone Type (PW-2521BMA)
For Middle Range : 10 cm Cone Type (PM-1021CM)
For High Range : 3 cm Dome Type (DH-2203CMA)
Nominal impedance 8 Ω
Playback frequency band 40 Hz to 20 kHz
Rated input 15W
Max Input 50W
Output sound pressure level 91dB/W (New JIS Display)
Crossover frequency 800 Hz, 5 kHz
Level control Mid-range : 3 positions (800 Hz to 5 kHz)
High frequency : 3 positions (5 kHz to 20 kHz)
External dimensions Width 345x Height 590x Depth 270 mm
Weight 15kg