I am not sure if this has been discused much regarding bass from a ported vs sealed design and if there is a difference in loading the room in the bass region. I have done some searching on the webs and have not found much about it.
Not much of a difference in room loading since at low frequencies the radiation pattern is omnidirectional. The port acts like another bass driver.
I have a set of sealed speakers that go down to 35 Hz, and a set of ported that go down to 55Hz.
The sealed speakers in this particular room sound very bad and the bass really just loads the room. On the other hand the ported design does not do this and sounds very good in the room.
Sounds like you have a small room that doesn't tolerate the long wavelengths of very low frequency from the bigger sealed woofer. Sealed has lower extension than ported so it is activating more LF modes in the room. But the woofer cone is too big and overloading the room. Smaller woofer cone will rolloff higher.
Try the small ported speakers in a different way: Seal the reflex ports on the smaller speaker with a sock. You'll get the benefits of sealed woofer and it will better match the room boost but not overload the room. If there's not enough bass move the speakers closer to the front wall. This also reduces distortion from SBIR to clean up the mid bass sound quality.
Assuming I can't do much to treat the room, does sealed and ported designs load bass in a room differently? Is bass .. just bass, and there is not any difference?
Yes, basically bass is just bass for box speakers regarding room loading. Box bass is omnidirectional. There's no significant difference other than the steeper rolloff with port and the higher distortion from the port.
Could there be a mode in my room from 55-35Z that is causing this, or could it be the internal compression of a sealed driver and the speaker reacting differently that a ported design that can release that internal pressure?....or both things happening? I am strongly considering open baffle subs. But this has been bugging me about not being able to use my sealed speakers.
There definitely is some room mode issues in every room everywhere.
Sealed and ported do work differently internally, but that's no cause for significantly higher distortion.
Try the sealed speakers in a larger room or outdoors. If they sound better then they are just too big. Add a series cap to line signal after preamp to roll off their bass a little steeper and starting a little higher. Adjust the cap size and speaker distance to the front wall to get the right bass level and minimizing SBIR. You can fine tune them to the smaller room. You can add the cap to an adapter or IC, don't have to mod the preamp.
What kind of speakers are they? What size is the room?