Rockford Fosgate RM18D4

• Sensitivity (1W, 1m, infinite baffle) SPL1W 84.5dB

Thiele & Small parameters

• Resonance frequency (free air) fS 41.5Hz
• Mechanical quality factor QMS 8.48
• Electrical quality factor QES 0.89
• Total quality factor QTS 0.81

Large signal parameters

• Maximum linear excursion xmax 7mm
• Air volume displaced at xmax VD 194cm³
• Power handling P 150W
• Program power Pmax 300W

Voice Coil

• Nominal impedance Z 2 x 4Ω
• DC resistance (in series) RE 6.3Ω
• Inductance (1kHz, in series) LE 2.48mH
• VC Diameter 38mm
• Former material Aluminum

Magnet

• Force factor (in series) Bl 12.5N/A
• Motor constant Bl/√RE 4.98N/√W
• Weight 0.5kg

Diaphragm

• Effective diameter 188mm
• Effective area SD 277cm²
• Moving mass MMS 84g
• Moving mass (without air load) MMD 81.1g

Suspensions

• Stiffness KMS 5.71N/mm
• Compliance CMS 175µm/N
• Equivalent volume to the compliance VAS 19L
• Mechanical resistance RMS 2.58N·s/m

Dimensions

• Nominal diameter 8″
• 203mm
• Baffle cutout diameter 177mm
• Mounting depth 92mm
• Volume occupied by the driver 1.42L