The speaker enclosure is a Mass Loaded - Tapered Quarter Wavelength Tube (ML-TQWT). As you can see, Martin has done a great job with the finish on the DIY speaker cabinet. He came up with the design on his own using the MathCAD worksheets available from Martin J. King at quarter-wave.com. His speaker project includes a design for a baffle step correction circuit which he found necessary to balance the sound.
Martin reports that the sound is relaxed with a detailed midrange and good highs. He also indicates that the ML-TQWT enclosure gets good low end extension from the small Fostex driver. Having recently used the FX120, I can confirm that this is one sweet sounding driver.
For additional information, pictures and the speaker cabinet design, see Martin's Fostex FX120 DIY ML-TQWT Speaker Project.
Related DIY Audio Projects:
- Fostex FX120 Bass Reflex Bookshelf Speaker Project
- Jordan JX92S Transmission Line Loudspeaker Project