Near identical twin.
Place Delta 12LF in 5.1cu ft. Made pathway with just a little expansion from driver to near port area (but not too close).
Sounded best when tuned to 35Hz. Perhaps -3 at 30Hz.
Beginning of pathway on 13 inch width interior was set 6.25 inches back so no real compression there IMO.

Purpose of experiment was to see if lower -3 was possible by reducing Fs of driver by having a pathway inside (but open to full width prior to port.

Observations:
It sounds pretty good I think. Seems to have reduced fs of driver by 5Hz.
Seems to go lower but less punchy. Making it sound just a little less loud.
Did try tuning the one without the pathway a little lower and then it did not sound good.
No increase of volume from "inside of speaker horn" at least not with the size of port chosen.

Questions:
Should this not have produced some possible phase problems?
Maybe there is an I'm not hearing it yet?
Maybe what I hear as punchy in the one without pathway is the way is should be and the other is a phase issue on the one with the pathway?
Is there a better way to reduce fs and get a speaker to go lower in a given size box? (one that does not infringe on the patents of others)

Any input would be appreciated.
Barry