[Poultrygeist]

Decware states they wanted to suppress the backwave, at least the part that reflects off the front wall, which increases speaker placement options.  Another factor is they wanted to load the Fast-15 driver with the floor because Fast-15 has lower Qts than F15 and really requires a larger baffle to extract enough bass response if on normal vertical baffles. 

Who knows.  I plan to try them sitting on wood floors not carpet and see what happens.  If it doesn't work out, carpet/rugs!

A box enclosure suppresses the back wave while OB's embrace the back wave. The back wave is what sets OB's apart from box speakers.

[Jon L]

A box enclosure suppresses the back wave while OB's embrace the back wave. The back wave is what sets OB's apart from box speakers.

I already made traditional open baffle speakers with Zenith 12" 49CZ852 so time to have some fun experimenting.  It seems like Decware is trading backwave soundstaging for ceiling bounce while keeping box resonance out.  If I don't like the ZROB tilt, I can always flip the baffle upside down and set it up vertical.   

[Jon L]

Breaking in the Fast-15 drivers 

[Poultrygeist]

The Fast-15 has a QTS of .52 while the F-15 is .71. In general single drivers with a minimum QTS of .7 or higher are better suited for open baffles while lower QTS drivers depend on the air spring action that a box enclosure provides.

[Jon L]

The Fast-15 has a QTS of .52 while the F-15 is .71. In general single drivers with a minimum QTS of .7 or higher are better suited for open baffles while lower QTS drivers depend on the air spring action that a box enclosure provides.

That is partly why Decware designed the Zrob, so the Fast-15 does get some air spring action from the floor.  The bass does sound quite impactful and solid.  Decware also claims Fast-15 has a "rising upper response" which worked better with the built-in off-axis vertical listening position.  Having tried on and off-axis vertically, he may have something here.  

[Poultrygeist]

I found the F-15 with its higher QTS to need bass support. I believe the Fast-15 with its lower QTS would also benefit from bass reinforcement.