Commentary

A woofer system using the largest woofer unit of Diatone developed in 1980.

The unit is equipped with PW 1600 which is a 160 cm cone type woofer.
A honeycomb diaphragm is used for the diaphragm. Aluminum alloy is used for the honeycomb core and CFRP (carbon fiber reinforced plastic) is used for the skin material to realize weight reduction. The weight of the diaphragm is reduced to 3 kg even though it is a super large woofer.
We have also adopted a field coil for the magnetic circuit. At the design stage, when calculated using permanent magnets, the weight exceeds 800 kg even if a strong magnet is used. Therefore, we have decided to use a field coil to reduce the weight. This coil uses electric wires for train motors, and the field coil alone weighs 400 kg.
A high heat-resistant bobbin is used for the voice coil to achieve high input resistance.
Since the frame cannot be cast as a single unit, four parts are assembled with bolts. This unit weighs 600 kg as a single unit.

The enclosure uses a bass-reflex system and is made of a steel balk covered with wood.

It seems that the unit with the unusual size of 160 cm had a lot of difficulty in the characteristic test.
At the Koriyama Test at the Koriyama Factory was carried out in the measurement room at first, but it was stopped because fluorescent lamps on the ceiling fell due to vibration. It seems that the characteristic test was carried out at the ground in the factory premises.
The outdoor test seemed to have a negative impact on the neighborhood. At a distance of about 100m from the speaker, it was felt as sound, but at a distance of more than that, it was transmitted as vibration and earth rumbling instead of audible sound. Within a radius of 2 km from the factory, there were damages such as vibrations like earthquakes and earth rumbling, and sound of walls and windows.

The first one opened to the public was Kobe Portpia Mitsubishi Miraikan in March 1981.
In addition, it seems to have been used in a quiz program on Tokyo Broadcasting System at that time to ask, "If you ring it in the prefabricated house, will the window glass break?" It seems that the glass broke easily.

It seems that this speaker has been delivered to laboratories of kobe university and Central Research Institute of Electric Power Industry which study noise and vibration.

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