On the topic of port contours and flares unfortunately this does not solve the issue of port pipe organ resonances.
On the AVS forums Erin has used Klippel to test and measure pipe organ resonance in number of JBL systems. From my observation the smaller LSR monitors suffer these problems. Yes it is audible according to Erin. This type resonance is a function of the enclosure air volume relative to the port air volume. A long port tube is required in a small enclosure volume compared to a shorter port in a larger enclosure of identical port tuning frequency.
The only definite solution is to use a passive radiator. Focal and several other near field monitor manufacturers have used passive radiators successfully.
In terms of overall listening satisfaction consider the following trade off:
Is an over damped bass reflex design using a low port tuning frequency with a long port more important than risking audible pipe resonances in the midrange?
In a small two way system probably not.
Looking at the alternatives with a 3 way system you can limit the bandwidth of the woofer to avoid pipe organ resonances. But this adds cost and complexity to a commercial product.
Adam and Focal both have premium 3 way near field monitors but they are beyond the budget of most home studio set ups.
The passive radiator suddenly becomes an appealing option. But suitable panel real estate is required. For this reason passive radiators are now available in rounded rectangular shapes.
An external powered sub woofer is another alternative. The main loudspeaker can use set up as a sealed enclosure while a seperate dedicated subwoofer uses an optimised bass reflex tuning. The advantages are powerful extended low bass. Tight upper bass and low colouration mid range.
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