As far what worked with your older deck not working now, input impedences on the recorder do have some effect on the bass rolloff settings on battery boxes. This is just part of learning new gear!
Good point. But depending on how different your recorder's input impedence is from the one the battery box is calibrated at, there can be a HUGE difference. Another reason why I never roll off with a battery box.
If battery boxes are still calibrated for a 10 Kohm impedance (like my 10 year old SP's one), since the HR's line in impedance is 15 the roll off you get would be 10/15 of the amount listed in the battery boxes instructions for each setting. (For mic in on the HR which has an impedance of 30, you would get only 10/30 of the listed amounts, a really huge difference).