Sorry guys, but the Flared port isn't the Nirvana anymore, the Contoured port now sits on the throne as King!
There's been some activity in modern times with regards to speaker enclosure vents or ports. Engineers have been giving more attention to bass reflex ports. JBL patended the Slipstream flared port, Bose patented one too, and as i recall a Pevey Engineer did so for another one. Manufacturers increasing their thinking and time for this device.
The flared idea (ends similar to a conical horn shape) remains in the Contoured port but its maximized, as well as on other aspects, the latter is seemingly larger size. Advanced aerodynamics are part of the solution here i guess.
However, the flared port's career doesn't appear to be over yet, far from it, due to an inevitable reason. The Contoured seems to be application specific, said otherwise cabinet specific, custom made for premium high performance or high power systems. Haven't seen off the shelf contoured ports for sale, they're probably low volume dedicated production items. Maybe available from a speaker manufacturer as repair parts to replace a broken one on a system for example??
The HLA series port looks like a variation of this where Engineers were able to get almost 3 db more output with it.
Don't throw away your older ABS or cardboard tubes. The good news is that the straight flanged port isn't so bad after all, still delivering quite acceptable performance for most use, providing the vent area is large enough to avoid air turbulence (Eargle: "A simple cylindrical port, as shown at (1) in figure 4-15A, works very well when the port is large enough in diameter so that air particle velocity is small", P. 82).
I'm not a pro drafter or artist but in order to give members here an idea of what a Contoured port looks like i made a hand sketch with a pen (probably 95% accurate) based on what Eargle reports and shows in his Loudspeaker Handbook.
Note on pic the contoured is larger, the tube in the middle is curved, not straight like a regular flared one, and the rear "horn" end seems a little smaller than the front one, which would make sense based on Harman Engineers paper on maximizing vent performance.
Please don't repost my sketch on other forum(s) or site(s).
Richard