ONKYO SL-1
¥ 150,000 (1 unit, around 1980)
Commentary
An active subwoofer that plays back very low frequencies from 20 Hz to 90 Hz.
The SL-1 is an acoustic transformer using a 38 cm flat passive radiator and a 20 cm driver. It is a sealed enclosure with an internal volume of approximately 80L. It is equipped with a 60W output PWM drive amplifier.
The unit is equipped with a 20 cm cone driver and a 38 cm passive radiator. By using a filter composed of these units and the front cavity to which they are connected, frequency characteristics close to band-pass characteristics are maintained and flat playback is achieved over the entire used band.
It has a built-in PWM (pulse width modulation) power amplifier with a rated output of 60W.
Because the SL-1 has a high-power amplifier built into an airtight box, special consideration must be given to internal temperature rise. The PWM method is suitable for such applications because it has less power loss with the same output than other types of amplifiers.
Model Rating
| Method | Built-in Amplifier, Acoustic Transformer / Passive Radiator |
| Units Used | Screwdriver : 20 cm cone type Passive radiator : 38 cm metamorphic type |
| Playback frequency band | 20 Hz to 90 Hz |
| Cut-off | 60, 70, 80 Hz 3-step switching |
| Input impedance | 10k Ω (high-level terminal) 100k Ω (low-level terminal) |
| Drive amplifier | PWM method, 60W rating |
| External dimensions | Width 620x Height 483x Depth 411 mm |
| Weight | 38.5kg |
| Power and power consumption | 100 VAC 50/60Hz 70W (Electrical Method Standard) |
| Remarks | Front panel controls : power switch Level control and cut-off frequency switching Rear panel operation function : Input sensitivity switching, phase switching |