Recommend you visit www.smr-forums.com where v4 has been discussed in great detail. These discussions include some very informative posts by the designer of v4.
v4 does not try to flatten the frequency response, but instead looks for lower freqency resonances (approximatley across the band of 16Hz to 250Hz), and reduces those resonances. Result not only tames out of control bass, but also reduces masking of other frequncies throughout the band so that everything is more clearly presented and better defined. v4 is a very high resolution room correction equalization. Set up and operation are automated.
I bought the v4 upgrade. Have not installed it yet but my expectations are high. Many at SMR have first hand experience using v4.
Thanks
Bruce