4 Inch (102 mm) 8 Ohm, Carbon Fiber Midbass Woofer

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This 4 inch midbass woofer is perfect for a wide variety of high-end audio systems, whether a 2-way bookshelf speaker, a multi-driver floor standing speaker, or a professional line array. A rigid but lightweight carbon fiber cone and an edge-wound copper voice coil combine for excellent transient response and an extended and controlled upper roll-off. The frame is heavy-duty, aluminum die cast with venting below the flat spider and through the center of the magnet structure to avoid air turbulence and noise. This is a premium, well-crafted speaker designed to bring music to life.

  • Lightweight, rigid carbon fiber cone with rubber surround
  • 2.6 mm, Klippel verified minimum Xmax
  • Vented, square-cast aluminum basket
  • 1 inch voice coil, edge-wound copper on Kapton form
  • Wide frequency range, 60 to 12kHz
  • 0.9 kg, (2.1 lb) net weight

Bold North Audio products are the most accurate, engineered audio transducers available. Each design requires Klippel vibrational test analyses to verify the key parts of optimal audio performance. While we rely heavily on objective science to lead us, we understand that most of all speakers need to tell the musical truth. Our engineers, musicians, and recording studio veterans are the final judges of when a design is worthy of the Bold North Audio brand.

All Bold North Audio products are assembled in Minnesota, with parts sourced from around the world to produce the highest combination of performance, consistency, and customer value.

More Information
Model # BMW-4001
Speaker Type Midbass
Size, Nominal (inch & mm) 4" (100 mm)
Shape of Speaker Square
Application High-End Audio and Home Theater, Home Audio, Indoor, Pro Sound
RoHS Compliant Yes
Rated Impedance (Ω) 8
DC Resistance (Re) (Ω) 6.4
Rated Power IEC268-5 (W) 25 Watts
Continuous Power (W) 25
Program Power (W) 50
Frequency Range (Hz) 60 - 12,000
Sensitivity (dB SPL) ¹ 88
Resonant Frequency (Fs) (Hz) +/- 15% 68
Nominal Impedance (Z) (Ω) 8
Voice Coil Inductance (Le) (mH) 0.33
Mechanical Q Factor (Qms) 8.30
Electrical Q Factor (Qes) 0.34
Total Q Factor (Qts) 0.33
Moving Mass (Mms) (gm) 6.49
Suspension Compliance (Cms) (mm/N) 0.84
Mechanical Resistance (Rms) (kg/s) 0.34
Surface Area of Diaphragm (Sd) (cm²) 52.8
Compliance Equivalent Volume (Vas) (L) 3.31
Motor Force Factor (BL) (T•M) 7.23
Efficiency (η₀) (%) 0.30
Efficiency Bandwidth Product (EBP) (Fs/Qes) 200
Basket Type Cast aluminum
Voice Coil Diameter (mm) 25.4
Voice Coil Wire Material Copper
Voice Coil Former Material Kapton
Magnet Material Ferrite
Magnet Weight (g) 340.19
Cone Body Material Carbon fiber
Cone Surround Material Rubber
Spider Material Cotton
Net Weight (kg) 0.95