Eighteen Sound 8M400F

• Sensitivity (1W, 1m, infinite baffle) SPL1W 96.5dB
• Frequency response 200 - 9000Hz

Thiele & Small parameters

• Resonance frequency (free air) fS 89Hz
• Mechanical quality factor QMS 4.03
• Electrical quality factor QES 0.28
• Total quality factor QTS 0.26

Large signal parameters

• Maximum linear excursion xmax 3mm
• Air volume displaced at xmax VD 68cm³
• Power handling P 250W
• Program power Pmax 320W

Voice Coil

• Nominal impedance Z 8Ω
• DC resistance RE 5.1Ω
• Inductance (1kHz) LE 0.7mH
• VC Diameter 51mm

Magnet

• Force factor Bl 13.1N/A
• Motor constant Bl/√RE 5.8N/√W

Diaphragm

• Effective diameter 170mm
• Effective area SD 227cm²
• Moving mass MMS 16.9g
• Moving mass (without air load) MMD 14.4g

Suspensions

• Stiffness KMS 5.29N/mm
• Compliance CMS 189µm/N
• Equivalent volume to the compliance VAS 13.7L
• Mechanical resistance RMS 2.35N·s/m

Dimensions

• Nominal diameter 8″
• 210mm
• Overall diameter 210mm
• Baffle cutout diameter 186mm
• Overall depth 106mm
• Flange thickness 15mm
• Mounting depth 91mm
• Volume occupied by the driver (estimated) 1.5L
• Net weight 4.9kg