I believe that the driver and vent responses are fully summed and room effects are mostly avoided, correct me if this assumption is wrong. More telling to see what goes on in the lower octaves are near-slot measurements, where I place the microphone on the K-slot's plane a bit above the driver's axis, where the slot is 2' wide or so. As all other measurements in this post, I only post the region of interest from 20Hz to 2kHz. Here is the response at 50cm, cabinet elevated 25' from the floor. The short shelf board now reaches all the way to the back panel, but has four 1.5' holes and likely does not contribute much in the way of tuning, or could I be wrong? The venting was originally done mid-cab through the short horizontal shelf board, but is now four 1' holes at the top of the reflector panel.

Here is the plan for dimensional reference. I though I could pin these down to standing waves easily, but am not certain after measuring acoustically VS physically. My present TK6 is interesting as it has all the warts present, of non-negligible magnitude to boot. The SK8 had the better response, with a dip or two and no major peaking. I built a K12 and Super-K8 (really a K10) in the past and took measurement, but lost most of those. A Karlson's frequency response is often pretty horrendous, being marred by peaks and nulls. There are some measurements in the thread, but I will post the ones I think are more relevant here. I initially went with a midbass, but finding it unsuitable for the enclosure, I since moved to FF125K and now dual FF125K. The below link is a recent build of mine, a high aspect ratio Karlson for 6' drivers, which I dubbed Tall K6, TK6 for short. I'm posting this in Fullrange since most Karlson enthusiasts seem to hang out here.

Vent direct sound drivers