So this design should ultimately aid in extraction of a better low end...Officially called a "restricted terminus”. It provides mass-loading which adds another low pass filter in the design, allowing for less damping and more fundemental to reinforce the bottom.
dave
Regards
Brother just one clarification
the original Sibelius speaker has a narrow duct while your design has a much wider duct ... any difference in the design...
Yes, Sibelius uses a special driver, has a narrow duct area, short duct length, and unknown sound absorbing material.
DDVP has a larger duct area, longer duct length, and less sound-absorbing material.