SONY APM-33W

Commentary

This is a bookshelf type speaker system that utilizes the know-how accumulated through the APM-6Monitor and adopts SONY's original APM unit.

In the APM speaker, the flat diaphragm eliminates the cavity effect, which is the resonance phenomenon of air that occurs in the conventional megaphone-shaped cone, and prevents the frequency characteristics from being disturbed.
This flat diaphragm adopts the honeycomb sandwich structure used in aircraft and Shinkansen bodies. By sandwiching the honeycomb core in the shape of a hexagonal honeycomb honeycomb with two sheets of skin made of aluminum foil, the bending rigidity reaches 500 to 1000 times that of the conventional cone type, and deformation is suppressed to 1/20 to 1/30 even in actual use. This has succeeded in minimizing split vibration.
In addition, the vibration pattern of the diaphragm is simplified by adopting a square shape with a simpler division vibration pattern than the round shape, and the division vibration of a specific mode is eliminated by using the milestones (points that do not move) of the division vibration pattern as driving points.

324 cm, equivalent to 20 cm, in the lower range²Equipped with a flat woofer.
It uses a flat diaphragm sandwiched between aluminum honeycomb and aluminum skin. Four driving points are chosen as the points where the milestones (points that do not move) of the low-order mode of divided vibration are concentrated. It is driven by four armatures directly connected to the voice coil. By this method, divided vibration in the used band is eliminated and the pistnick motion band is expanded.

16 cm, equivalent to 4.5 cm, in the high-frequency range²Equipped with a planar type tweeter.
The diaphragm has the same structure as the woofer, which sandwiches aluminum honeycomb with aluminum skin. The large voice coil drives the point to cancel the split vibration, so that the split vibration within the audible band is almost completely eliminated.

The network section is designed to take advantage of the capabilities of the APM unit. The internal wiring is made of oxygen-free copper wires with excellent transmission characteristics, and several types of capacitors with excellent sound quality are used in parallel. In addition, high-quality air-core coils are used to minimize loss.
In addition, it is equipped with level control so that it can be adjusted according to the room.

The sound of the enclosure is improved by controlling the vibration of the inner surface and outer periphery of the back plate with fine grooves.
In addition, three types of sound absorbing materials are selectively used to control the sound inherent to the sound absorbing material and achieve a natural sound absorbing effect.

There was a special speaker stand sold separately.

Model Rating

Method	2-Way, 2-Speaker, Bass Reflex System, Bookshelf Type
Unit	For low band : 324 cm2Plane type For high band : 16 cm2Plane type
Playback frequency band	39 Hz to 20000 Hz
Output sound pressure level	91dB/W/m
Impedance	6 Ω
Instantaneous maximum input	160W
Rated maximum input	80W
Crossover frequency	2.2kHz
Level control	+ 0 to -50dB continuously variable
External dimensions	Width 315x Height 540x Depth 320 mm
Weight	14.4kg
Attachment	Speaker cord
Speaker Stand WS stand WS-300 (1 set of 2, ¥ 6,000)
External dimensions	Width 295x Height 140x Depth 290 mm
Weight	Approx. 3.0 kg