Subwoofer boom is too much for me...

1. Sell the ported sub.

2. Buy 4 sealed subs.

3. Do some research on distributed bass arrays.

4. You're welcome.

Real curious about what sub you have.

Years ago, my first sub, was nothing but boom. It was a low price Yamaha. 

Next sub was a Definitive Technology prosub 1000. It was better, but still had a little boom to it. In hindsight, I figure it was intended to serve in HT.

Got tired of playing that game and went to a REL 10" sub and found nirvana. Properly set up, a good sub is hard to notice, except for a little more depth and better definition of low frequencies.

@kota1  +1

I would think that a port needs to be plugged with something that seals it, like the foam plugs that come with some subs.  Maybe cut a piece off of a solid foam pool noodle.

Tony1954 above has the answer. I would do the same. But I already did.