This really depends on the method of cooling the manufacturer uses. But most of the time outside the box, the cooling vents are drawing cooler air than they would in an enclosure. A lot bigger volume of air outside the enclosure than in.
Not true at all , I have personally heard mechanical noise from some of the most sought after subwoofers in the business. All though the mechanical noise was slight on most of them. It was still there, and they were bnib. Coils checked out fine. No physical scraping or touching at all. 3 of the same prominent drivers all made the same exact noise. 2 of the same drivers from a different company....... noise. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif