SONY SS-7400 ULM4
¥ 45,000 (1 unit, around 1971)
Commentary
This is a speaker system developed by Sony Corp. after conducting basic research on speakers from scratch.
We have developed and adopted a new magnetic circuit that theoretically clarified the distortion caused by the magnetic circuit and eliminated the harmful effects.
In ULM speakers, the structure of the magnetic circuit is different from the conventional one.
In order to prevent the occurrence of non-linear distortion in the magnetic circuit of the speaker, two improvements have been made to eliminate the non-linear distortion of the magnetic material by creating a notch in the center of the center pole and adding a thick copper plating or copper cap to the notch.
The voice coil uses a newly developed special synthetic resin adhesive after careful consideration of heat resistance and mechanical strength, and the woofer uses a metal bobbin to raise the allowable input.
30 cm and 12 cm cone type units are used for the low and middle range, respectively.
We have thoroughly studied the types and processing methods of pulp, which is the material for corn paper, and used corn paper which is excellent in theoretically and audibly.
In addition, the edge is made by applying a special thin rubber to the cloth for airtight treatment and molding. Therefore, the valley which tends to occur around 400 hz is taken, and smooth characteristics are realized.
In addition, high-purity imported copper foil processed with special resin is used for the lead wire to prevent breakage, extending the life by more than 10 times.
A 2.5 cm dome type tweeter is used for the high range.
To improve the frequency response, we have developed a special equalizer (diffuser) to obtain smooth response.
The enclosure is a walnut finished bass-reflex structure.
The baffle on which the unit is mounted has no decorative edges, and the Saran frame has a streamlined shape with no brim to avoid harmful reflections and interferences.
It is equipped with level control so that it can be adjusted to the acoustic characteristics of the room.
Built-in continuously variable level control for + / - 3 dB control of tweeter and mid-range levels.
It has a multi-selector switch and a switch to disconnect the LC network so that you can drive the woofer, mid-range and tweeter directly.
Model Rating
Method | 3-Way, 3-Speaker, Bass reflex system, Bookshelf Type |
Unit | For low band : 30 cm cone type For Medium Range : 12 cm cone type For high-pass : 2.5 cm dome type |
Playback frequency band | 40 Hz to 20000 Hz |
Output sound pressure level | 91dB/W/m (New JIS) 97dB/W/0.5m (Old JIS) |
Impedance | 6 Ω |
Maximum allowable input | 100W (weighted pink noise 24-hour guarantee) |
Crossover frequency | 600 Hz, 4500 Hz |
External dimensions | Width 415x Height 680x Depth 300 mm |
Weight | Approx. 21 kg |