31NFR

The 31NFR is a high efficiency, (84dB 1watt / 1 meter) 3-inch full range speaker with very linear frequency response characteristics and high power handling capability. The 31NFR uses a lightweight anodized aluminum cone assembly along with a NBR single roll geometry surround. The combination provides high efficiency, extended high frequency response and sustained output under variety of conditions, while generating low harmonic distortion over the working range of this speaker.

Magnetic circuit design
REDCATT engineers have developed neodymium based magnetic circuit with small form factor, high integrity magnetic flux gap and low distortion characteristic. The magnetic circuit design is optimized to generate the minimum amount of flux modulation, providing exceptional stability. Copper demodulation cup is assembled over the t-pole.

The 31NFRX8-229 is a 3-inch full-range driver featuring a hard anodized aluminum cone, neodymium magnetic circuit with a copper demodulation cup, and exceptionally low mechanical damping (Qms = 15.1, Rms = 0.12 N.s/m), designed for Hi-Fi column speakers, outdoor products, and multi-way systems requiring the highest power handling and lowest bass extension in the full-range driver family. The aluminum cone is driven by a 25.4mm voice coil on a Kapton former, with an NBR single-roll surround and Nomex spider in a lightweight plastic basket. Sensitivity is 83.49 dB (1W/1m) / 84.49 dB (2.83V/1m) with a Bl of 3.5 T.m, supporting 30W AES / 60W continuous - the highest rated power and maximum SPL (98.3 dB at 1 metre) of the six-variant full-range family. The copper demodulation cup over the T-pole reduces position-dependent flux modulation, lowering second-harmonic distortion at drive levels throughout the Xmax stroke. Qts = 0.88 combined with the lowest Fs in the family (115 Hz) produces a free-air f-3dB of approximately 97 Hz - the only driver in the full-range family to break below 100 Hz in open-back installation without DSP correction.

- 2,920 mL / Qtc=1.00 / f-3dB 103 Hz - largest practical sealed; only 6 Hz worse than free-air
- 988 mL / Qtc=1.20 / f-3dB 116 Hz - practical column rear chamber; DSP correction needed
- 446 mL / Qtc=1.50 / f-3dB 137 Hz - compact sealed for portable products; full DSP required

Amplification of 30-60W from an 8ohm amplifier output is appropriate, with a mandatory high-pass filter at 70-90 Hz. The aluminum cone provides rigid pistonic behavior and extended high-frequency response up to the 3,650 Hz cone beaming onset; hard anodizing attenuates breakup resonances above this point. In multi-way crossover designs, crossing below 3,500 Hz eliminates both directivity narrowing and exposure to potential upper breakup modes. In column array applications, the 78.7mm driver OD limits coherent vertical directivity to approximately 2.2 kHz. The inductance rolloff onset at 11,150 Hz is beyond the audio band. A Zobel network (6.3ohm + 2.3 uF in series across driver terminals) is recommended for passive network designs. The 31NFRX8-229 is suited for Hi-Fi column speaker systems requiring sub-100 Hz natural bass extension and maximum SPL from a full-range 3-inch driver; outdoor and semi-outdoor installations where NBR surround durability and neodymium motor stability are required; multi-way systems as the primary full-range element with a subwoofer crossed above 80 Hz; and portable and professional audio products where the highest power-to-size ratio in the full-range family is the principal design criterion.