ML SL3 Bass resonance

Hi guys, I have already changed my new panels from the sequel II to my recently purchased sl3. The sound of the new panels is now brighter, I don't know if it will be due to the high voltage supply or the filter of the sl3, I suppose I will have to get used to it.
One thing that I don't quite understand about the sl3 is that it has a resonance peak at 76Hz that the sequel does not have, could it be because of the height of the wooffers? I have looked to make a notch in the filter but I would need an 8.3 mH coil, too big I think.
Has anyone had any experience on it?
Thanks