Set the speaker size to "small" in speaker configuration and set the speaker cross over to "80 hz" . Try > 80 hz if it does not improve crispiness still.
Also try adjusting the speaker distances manually to higher value than that's set currently. Try above "14" or "15" feet or equalent "cms" setting speaker distances. this should improve crispiness.
Also You should have "bass" , "treble" control in older model of onkyo. u should be able to change it.
if your model is new then you should have Equalizer control to change the tonal control. For that u need to switch off "audyssey" or any other room correction available in your avr model.
Also try changing the different listening modes.