SI - IMHO, yes it does. I've competed in the 12 volt industry for more years than I care to remember & it's been my experience that it's easier to tune a speaker playing in a fixed airspace. That doesn't mean that standard components won't sound good in OEM door locations but it seems that midrange & midbass sound "tighter" in a sealed enclosure; again, IMHO. I actually originally put the 5WS Utopias in the doors ( in a standard infinite baffle ( "free air" ) configuration but the midbass wasn't as tight as I wanted ( even with the use of Dynasorb ). A fellow competitor suggested the sealed enclosures ( in fact, HE made those for me - thanks, John!! ) & given my taste in music ( more along the jazz & old school rock ), I'm quite pleased.
Now if I can talk my ex-wife into letting me remove my old RF Symmetry from her/my GS400, then I can get REALLY serious!!

 

Superman - The 5WS requires a range of .25 to 1 cubic feet for a sealed enclosure but they also work OK in an infinite baffle mode. I spoke with a Focal tech & asked for his/their recommendations for my application ( tight midbass w/quick transient response time ). His idea was to fabricate a 1/3 cube sealed enclosure & tune for somewhere in the 80-100 Hz range ( the 5WS goes from 45 - 2500 Hz ).
I agree that too small an enclosure isn't the best thing either. As far as my setup being "better" than using the door as the enclosure - no, I'm not going that far. I've just found it easier to control the speakers' backwave in a sealed enclosure & therefore it sounds ( again, IMHO ) "tighter". My GS400 had a 7" Focal Xpert series midbass in the front doors & used the doors as the enclosure & I'm hard pressed to choose which of my 2 systems sounds best. I TRULY believe the Lexus was better because I had more power ( cleaner ); an Alpine H/U ( cleaner signal via higher output voltage ) & the ultimate ( once again, IMHO ) processor in the RF Symmetry w/28 band EQ card. Still, I'm very happy with my G's sound - just gotta get that Vortech in there now!!!

 

Yes, my old biz partner was an IASCA competitor whose motto was, "small sealed enclosures, lots of power, and a 30-band EQ".

 

finally done.

 

Looks great.