First off, let me explain that I don't have access to my car at the moment, so I can't give any specific information, so this will remain a general question.
I have an 8" sub in my trunk, in a ported box. For some reason, the bass gets a lot deeper (and sounds better) when I open the trunk slightly. Is there something wrong? This is on a car with a closed trunk (not a hatchback or open connection to the passenger compartment).
Opening the trunk in essence creates a tuned port. It is the very same reason that your box is ported. Once the trunk is open, you have effectively used the entire trunk as a ported box. More volume = better sound (in general).
I can only assume (*** u me) that you mean it sounds louder in the car, with the windows up?
Otherwise, if by chance you mean that it gets louder while standing next to the trunk, then you're just letting the sound get out.
So, the more rational of the two would be that it gets louder while you're in the car.
Then what Jackso said would be true. (Not saying you're lying) :)
Could it be that your box isn't tuned properly and the trunk is affecting (adversely) the parameters (Thiele/Small) etc. Of course a sub will sound different in a larger space than a smaller space.
You may want to port the sound into the cabin from the trunk, perhaps through your rear deck, if you've got one.
Yes, I mean when I'm in the car. I thought the opposite would happen because you're letting the sound out of the trunk. But while inside the car I push the button for the trunk release and the sound improves inside the car. The bass is stronger.
I'll admit now that I'm not all that familiar with the technical side of sub woofers and sound systems. The sound I want for my car is to have bass in the car, not a hundred yards in front of it.
I have a small rear deck and was thinking of doing just that. Very interesting.
Thanks for the responses.