ONKYO FRX-20

Commentary

A 20 cm cone type full range unit that uses specially molded 2-layer urethane edge and elliptical cone technology.

A newly developed special elliptical cone is used for the diaphragm.
This diaphragm uses a composite curve calculated using a computer to suppress peaks and dips in the middle and high frequencies, which are the most problematic in the large diameter full range. The edge and center are perfectly round, but the curvature differs in the longitudinal direction and the lateral direction, and the intermediate section is shaped to be an ellipse. This allows the rigidity of the cone to change from the center to the outer circumference, dispersing and canceling the modes of divided vibration generated in the high frequencies.
Together with carefully selected materials, it achieves flat characteristics in the main band from 40 hz to 9 khz.

A dome containing carbon fiber with high density is adopted for the cap at the center of the cone, and it is used as a radiator for the band of 9 kHz or more.
This radiator is formed into a dome shape with an ultra-thin plastic film sandwiched between two carbon fiber plates with a mixing ratio of more than 80%. Compared corn with a high pulp content, this radiator has greater rigidity (more than 20 times that of duralumin) and superior internal loss due to the use of plastic film.
This realizes excellent high-frequency response and transient characteristics.

Specially molded 2-layer urethane edge is used for the edge part.
Two types of urethane foam with different physical properties are bonded together at a ratio of 3 : 5. The upper layer is an ester-based single-bubble type and the lower layer is an ether-based continuous-bubble type. The foam is then molded into a special shape that gradually decreases in density from the cone side to the frame side.
As a result, it has a linear response to the strong motion of the cone of the Oshin woman, and realizes flat characteristics while suppressing non-linear distortion.

The magnetic circuit uses a large Alnico magnet of 55 φ x35mm and a round yoke of 10 mm or more in thickness with low magnetic resistance.
A copper cap is attached to the center pole to reduce strain and prevent impedance rise in the middle and high range, and the top plate is thinner inside to improve the magnetic flux density and to make the magnetic flux distribution symmetrical.

Model Rating

Type	20 cm cone type full range speaker
Impedance	8 Ω
Lowest resonance frequency	45Hz
Output sound pressure level	93dB/W/m
Frequency characteristic	Fo ~ 18 kHz
Max Input	40W
Voice Coil Diameter	50 φ mm
Magnetic flux density	11,000gauss
Magnet size	55 φ mmx35mm
Magnet weight	611gr
Qo	0.45
Mo	10.5g
External dimensions	Diameter 232x Depth 118.5 mm
Weight	4.0kg