25NFR

25NFR was designed around neodymium ring magnet. The magnetic structure delivers very high level of magnetic force, while generating minimum amount of modulation distortion.
The lightweight, yet strong, paper cone with attached rubber surround was designed and optimized to deliver the highest level of performance in full-range applications.

This speaker finds its best application in columns or multi-way Hi-Fi products. Due to its excellent HF response, further usage of HF units is not required.
The small form-factor allows this product to be used in space limited applications or portable products.

The 25NFRX8-279 is a 2.5-inch full-range driver built around a neodymium ring magnetic circuit - distinct from the axial slug topology used in the 20/21/22NFR variants - designed to deliver genuine bass extension from a compact form factor for column speakers, multi-way Hi-Fi products, and portable applications. The glass fiber reinforced paper cone is coupled to an NBR rubber surround and Nomex spider, driven by a ~20mm CCAW voice coil on a Kapton former. Sensitivity is 82.34 dB (1W/1m) / 82.69 dB (2.83V/1m) with a Bl of 4.0 T.m, supporting 20W AES / 40W continuous power handling. Qts = 0.71 places this driver in a near-Butterworth condition in free air, with a natural system f-3dB of approximately 123 Hz - the lowest of the four NFR variants - providing the broadest usable bass bandwidth without equalization correction.

- 468 mL / Qtc=1.00 / f-3dB 136 Hz - largest practical sealed; modest DSP correction
- 248 mL / Qtc=1.20 / f-3dB 153 Hz - compact sealed for portable or soundbar use
- 133 mL / Qtc=1.50 / f-3dB 182 Hz - minimal cavity; full DSP management required

Amplification of 20-40W from an 8ohm amplifier output is appropriate, delivering a peak SPL of 95.4 dB at 1 metre (20W AES). With 2.65mm Xmax and 5.62 cm3 volume displacement - the largest Vd in the NFR family - DSP-assisted bass extension to approximately 80 Hz is achievable within mechanical limits, providing a meaningful headroom advantage over the 21NFR (2.0 cm3) and 22NFR (1.19 cm3). The neodymium ring motor provides inherently lower flux modulation distortion at excursion, supporting low-distortion performance when bass equalization is applied. The inductance rolloff onset at 12,920 Hz is beyond the audio band, and cone beaming onset at 4,215 Hz defines the upper dispersion limit. In column array applications, the 65mm driver OD limits coherent vertical directivity to approximately 2.6 kHz. The 25NFRX8-279 is suited for vertical column speaker arrays requiring genuine bass coverage without a dedicated woofer; multi-way Hi-Fi systems as a full-range element crossed above 80 Hz to a subwoofer; compact portable speakers where DSP-extended bass response from a 2.5-inch driver is a design objective; and outdoor or semi-outdoor column and surface-mount enclosures where the NBR surround provides long-term environmental durability.