I'll take a shot and say you are used to the way these songs sound on your old speakers which might not have had a flat response and boosted the bass a little too much and as the others have stated you are not looking for extremely low bass, ie. 20 hz and lower unless you are listening to pipe organ music. Most music bass is 30 hz and up and for the most part as was previously stated , 60 hz and up to provide that punchy bass, is what most are looking for from music and your M80s are more than capable of producing these frequencies. 65 SPL is pretty low volume for a speaker to play bass frequencies with authority(noticeable) unless they have a boosted FR in this region or some other anomaly that gives perceived better bass.

You could always add some bass boost via the receiver to enhance the response for low level SPL listening.
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Jason
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TTTHHHPPPPPTTTT!

My HT