My measurement is certainly not precise, but you can see that the "regular" version has a little more detail than the "pro".Do u know how the HE 150 compares to the pro version?
I guess that both models use the same driver. Cables and shells are different, but I think that different cover on the driver
greatly affects the change in sound (metal mesh vs plastic).
The shell on the PRO version seams nice from the outside. I didn't open my PRO but I saw some wrong design decisions for the shell interior
which drastically deteriorate the sound quality. For example HEADROOM MS16 shell is quite reminiscent of HE150Pro but inside it looks like this.
There is no point in listing what is wrong here, mostly everything, this is a nightmare for sound.