In this blog post I test the Fostex FW208HS in a 40L bass reflex enclosure tuned to 40Hz. The Fostex retails for $273 USD each and fits in the premium woofer category.
I've been using this woofer in a variety of projects over the past few years. It is a flexible woofer that responds well to a variety of cabinet tunings. It has a relatively punchy sound character compared to most 8" woofers I've tested. While it may not match the low distortion and dynamics of a 12" or 15" woofer, it gets pretty close and has the small size factor going for it for smaller setups. In other words, many 8" woofers I've tested simply sound too soft. If you are looking for a good 8" that offers some life, this may be one to consider. This woofer has been around for a few decades in various versions, and so it ascribes to a more 'classic' design parameter, which may be why I prefer this woofer's sound compared to more modern drivers. Some may say this is attributable to the high QMS of 12.9 where most modern woofers hover around a QMS of about 5.0.
Features:
- High stiffness diaphragm.
- High input tolerance long voice coil.
- Ø145mm large ferrite magnet.
- Low current distortion magnetic circuit.
- Adequate acoustic parameters.
- Aluminum die-cast frame.
I conducted a ground plane measurements with the mic at 50cm. My test cabinet uses a rear facing 3" port, which explains the dip at tuning.
Distortion remains around 0.10%for the 85dB 1m test signal.
For IMD at 85dB 1m we see performance hovering around the -55dB mark or better. For comparison a 15" woofer will offer IMD at around -60dB.
If we limit bass frequencies we see IMD improve to an impressive -60dB. 
Burst decay shows some breakup just before 2kHz. 
The CSD plot confirms the same.
Conclusion
The Fostex FW208HS offers excellent performance in this size and cost category.