by tuned I mean the resonance tuning of the enclosure. when ford (or whoever) designed those, they have a team that runs the math for harmonic resonance of the enclosure with that speaker. its not anything-that-can-be-adjusted-tuned, just the way its designed. again, some study time spent toward sound wave theory will shed a lot of light on the matter of enclosures and speakers. if you wonder why anyone would ever go through the trouble of building their own box, thats where you'd find your answer.
heres a fun little story that still gets a couple chuckles once in a while.
my first system ever ('96) was a single 12" sub that I bought from meijer (a department store, for those not acquainted - anything but pro audio) that handled 250W pk. the cardboard box that the speaker came in had a perforated hole you could punch out for a temporary box - this isn't relevant but an interesting note. when i got the speaker home, I pulled out my sound theory book, which only consisted of maybe 150pgs - a short and very worthwhile read - and built my own box from scratch. every speaker size (8/10/12/15/etc) has its own basic resonance requirements, and the book i had outlined these specifics. most enclosures don't use a full-wavelength resonance tune (as these enclosures would be much larger). I decided to go with the larger box w/o ports for my single 12" sub (3.something cu ft) and when I finished it and took it for a spin, I found myself sitting in a parking lot next to someone with twin kickers, who heard my setup and thought I was running a powered 15" sub (the 12" was still going off of my stock '86 merc. topaz HU). when I showed him what speaker and enclosure was being used, he was awe struck. and asked if i'd build him a custom box. it was enough of a pain building my own, so I declined, however.
=p
because I used a less *harmonically* resonated box, I had fewer dips in response (the more you reduce the size of a box, the, more response gaps you'll get, and the less room for error there is in the cu ft resonance specs), and a much cleaner sound off of what was really just a throw-away speaker. if i had done the same thing to a single kicker comp with amp, I woulda blown the guy with twins right out of the water.
just a little example of what some study time in sound theory has to offer. and also why I'm trying to tell Roc here not to cut that 8" enclosure hole to fit a 12". basically going to ruin the box, because the 12" has different cu ft req's than an 8", and he'll probably get very poor resonance points, not to mention a decent bit of distortion. by that point he wont have to worry about hiding it so it's not stolen, because it will likely end up sounding like a chitty speaker/amp when he's actually got some decent equipment to work with. I could be totally wrong on the resonance though - he could get incredibly lucky and it might sound halfway decent after he's done, but IMO its a waste of both the 8" sub, and the enclosure it used to fit in.
