Are there ways to modify a sealed box?

Making it louder or stronger?

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spectra5
Kenwood excelon x201t
Kenwood KFC-W3085
jvc KD-G430

It is usually easier to build a custom box than try to modify a prefab. If you are thinking about porting it, building a new one to spec is a better idea.

Ok I'm looking at your sub's manual, and it is an 8 ohm free air sub, so you're better off just getting a different sub because your amp is only going to put out 150 watts. Even if you get another of the same sub, it's not going to perform well unless it is free air.

This is why i'm selling the sub and box.And picking something suitable for this dual sealed enclosure.
If your hinting that my setup is entirely not compatible...That's obvious...but expected for the price of next to nothing(for car audio).

easier? So it can be done?
I work with a bit of wood at work and am capable of using pricise measurements and the right tools.

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spectra5
Kenwood excelon x201t
Kenwood KFC-W3085
jvc KD-G430

If you wanted to port a sealed box just cut a hole and put a PVC pipe inside it. Building a box to spec is better because the box is tuned properly and made to function well with your sub. RE Audio has a great enclosure calculator for making slot ported boxes. All you do is plug in the dimensions and the width and length of the port. It calculates the tuning frequency and box volume.

Here it is:

RE Enclosure Calculator