SONY APM-77/APM-77W

Commentary

This is a bookshelf type speaker system that uses SONY's original APM (Acoustic Pistonic Motion) unit.

530 cm in the lower range²Equipped with a flat woofer.
The diaphragm uses a honeycomb sandwich structure in which an aluminum core is sandwiched by aluminum skins, and a damper is incorporated in the sandwich structure to suppress plate vibration.
This diaphragm is driven at four points by four magnetic circuits and a voice coil. The driving point is calculated as the point at which the pistic motion band is expanded by canceling the split vibration. Moreover, accurate pistic motion is ensured by installing a center suspension in the center of the diaphragm to prevent rolling.

27 cm in the middle area²Flat mid-range.
The diaphragm is constructed by sandwiching an aluminum honeycomb core with a carbon fiber sheet skin. The lightweight and highly rigid carbon fiber sheet suppresses split vibration at high frequencies.
There is only one voice coil, and it is driven by a low distortion magnetic circuit at the point where the divided vibration is canceled.

7 cm for the high range²Equipped with a planar type tweeter.
The diaphragm has a structure in which an aluminum honeycomb core is sandwiched by carbon fiber sheet skins to increase rigidity.
As in the mid-range, there is only one voice coil and it is driven at the point where the split vibration is canceled, and there is almost no split vibration mode in the audible band.

In the network section, the respective network boards for woofer, mid-range, and tweeter are separately arranged to reduce mutual interference.

The enclosure has a bass-reflex structure using high-density particle board.
Thin grooves are provided on the inner periphery of the baffle plate and the back plate to control the vibration frequency of each plate including the body plate and to control the sound.

There were APM-77 with dark metallic paint finish and APM-77W with walnut veneer finish.

Model Rating

Method	3-Way, 3-Speaker, Bass reflex system, Bookshelf Type
Unit	For low band : 530 cm2Plane type For Medium Range : 27 cm2Plane type For high frequency : 7 cm2Plane type
Playback frequency band	28 Hz to 30000 Hz
Output sound pressure level	90dB/W/m
Impedance	6 Ω
Instantaneous maximum input	200W
Rated maximum input	100W
Crossover frequency	700 Hz, 4.5 kHz
External dimensions	Width 405x Height 745x Depth 325 mm
Weight	32.0kg
Attachment	Speaker Cord (3m)
Speaker Stand WS stand WS-500 (1 set of 2, ¥ 8,500)
External dimensions	Width 360x Height 140x Depth 320 mm
Weight	Approx. 4.0 kg