I'm assuming the freq graph for the EP500 is only an estimate and not an actual measurement. It looks too even.
Nope, it is absolutely a real measurement. The reason it looks so smooth is that it was measured as a near-field response inside the anechoic chamber. Because the EP500v4 is a sealed sub, the near-field response is equivalent to the 4pi response once the SPL is corrected for 1M and the radiating area of the driver is taken into account. Just for fun these curves were compared to the original pole measurements for the v4 subs and they correlate perfectly. The new DSP algorithm for response correction also helps!
