Drivers ListFi Car Audio DriversSSD 18 D2

ManufactureFi Car Audio
Motor TypeOverhung
Driver Size18 "
Driver Weight45 lbs
Coil Diameter3 "
Coil MaterialAL
Manufacture's Xmax21 mm

TS Parameters (Measured by

Fs27.8 Hz
Res2.8 Ω
Le 1khz8.58 mH
Sd0.117 m2
Vas156.6 liters
Mms400.6 grams
Cms82 μm/N
BL19.61 Tm
BL2/Res137.3 N2/W
L/R Time Constant3.07 milliseconds
SplSens90.03 dB


This is Fi's most cost effective 18" driver. It shares many features with the Q18 driver and an obvious family resemblance. The 12 spoke cast frame is used as is the heavy paper cone and dust cap. The surround is the large foam half roll and the spiders are a double 8" spider. The leads were not sewn in on this particular driver. The coil is a 3" copper wire with a shorter winding height compared to the Q series coils. The motor is also slightly smaller and lighter. The magnet slug appears to be the same size but the back plate is reduced in size and depth slightly as is the top plate. The result is a slightly lighter moving mass and less geometric xmax. (21mm one way is the rating.) Motor force is also slightly less. This driver does not employ a shorting ring or other inductance controlling measures in the motor.

We are not sure if this is the current version of the driver or the previous version. The specs look close to the current version but the motor appears to differ from the pictures.

Looking at the impedance measurements and the measured response in a sealed enclosure shows that this driver has a rather aggressive top end roll off and pronounced peak in the response. This will limit the driver upper bass sensitivity and usefulness. During free air excursion testing for noise it behaved very similar to the other Fi produced drivers with a low level tapping sound even at moderate excursion that develops into a very loud knocking sound once the excursion reaches about 2" peak to peak or more. The SSD developed this noise earlier than the others likely due to the shorter xmax but in the end it has just as much xmech as the Q series due to the same or similar suspension components being used. The free air excursion videos capture some of this noise. There is also some motor noise from the vents in the frame at high excursion but it is overshadowed by the mechanical noises.

This driver offers a lot of displacement for a modest cost and weight.


Fi Car Audio 18" SSD 18 D2 Systems