4FR

4FR ferrite based mid-woofer was developed for applications where small size mid-woofer is required. Low resonant frequency and large cone excursion delivers seizable amounts of low frequencies. Yet, this driver delivers very good performance in mid-high frequency range.
Our engineers have chosen lightweight, yet strong, paper cone with rubber surround. Cone optimized shape brings remarkable strength of the piston and greatly improves harmonic distortion artifacts.
Overall this model delivers very good performance and is well balanced between performance - cost.

The 4FRX4-322 is a 4-inch full-range driver built around a ferrite magnetic
circuit, a steel basket, a paper cone with NBR rubber surround, Nomex spider, and
a 25.4mm copper voice coil wound on an aluminum former. The aluminum former provides
a direct conduction path from the voice coil to the magnetic structure, improving
thermal dissipation relative to a Kapton former and supporting the 30W AES / 60W
continuous power rating. The copper winding at Re = 3.5 ohm delivers full conductivity
at a 4 ohm nominal impedance - the only 4 ohm option in the 4-inch family. The
manufacturer describes this as a dual-use driver suited for both full-range and
mid-woofer applications, with a cone profile optimized for piston stiffness and
reduced harmonic distortion. This is the cost-effective, ferrite-based member of
the 4-inch group, positioned where the high motor force and ultra-low inductance
of the neodymium designs are not required.

Enclosure alignments:
- Sealed (primary):
2.12 L / Qtc = 0.707 / f-3dB = 107 Hz (Butterworth - flattest; large enclosure)
1.08 L / Qtc = 0.85 / f-3dB = 111 Hz (recommended - balanced size and bass)
0.67 L / Qtc = 1.00 / f-3dB = 119 Hz (compact)
0.42 L / Qtc = 1.20 / f-3dB = 134 Hz (very compact)
The Fs = 79 Hz produces the lowest sealed bass extension of any 4-inch driver in the
family - a 107 Hz f-3dB at the Butterworth alignment vs. 127 Hz (41FRX8, free-air)
or 87 Hz (40NFRX16, free-air).
- Vented (secondary) - 30 mm port:
1.5 L / Fb = 75 Hz / ~229 mm physical port / 9.4 m/s peak port velocity
2.0 L / Fb = 70 Hz / ~194 mm physical port / 8.8 m/s peak port velocity
3.0 L / Fb = 65 Hz / ~145 mm physical port / 8.1 m/s peak port velocity
All within the 17 m/s hi-fi port velocity limit; sealed preferred where chuffing
or construction simplicity is a concern.

In column array applications, the 105.5 mm OD limits coherent vertical directivity
to approximately 1.63 kHz; a co-located tweeter is mandatory for full-range coverage.
The 4 ohm nominal impedance should not be wired in parallel with other 4 ohm loads
without verifying amplifier minimum impedance rating.

The 4FRX4-322 is suited for sealed enclosure 2-way monitor and bookshelf systems
where a cost-effective 4-inch mid-woofer with the lowest sealed bass cutoff (107 Hz
Butterworth) in the 4-inch family and a usable high-frequency range to 2,700 Hz is
required; small bookshelf and satellite enclosures where the sealed box alignment
(0.42-2.12 L) allows compact or large-format cabinet designs without port construction;
background music and commercial installed sound applications where affordability and
sealed-box simplicity are the primary design criteria; and 2-way column speaker
systems where the 4 ohm impedance, sealed driver bay configuration, and low Fs
produce usable bass extension from a compact cabinet per driver bay.