leave them open. its like leaving a window cracked for a bass run. it will be louder than alll sealed believe it or not i lost 2db from sealing them. i was pissed
Seal them up with Duct tape. Run it. And if it makes it less db's take the tape off. Plus you should have some duct tape laying Around so it would be free upgrade.
It won't hurt anything to seal them up. VW Beetles were so air and water tight that they float and VW used it for an ad campaign. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
It does pop your ears when you shut the doors though!