The 4" Ford speaker has bass blocker cap integrated into the speaker assembly. Same story with the rear 4" Ford speakers. If you upgrade the Ford dash speakers, you will need to buy separate bass blockers for them since aftermarket speakers do not include them. The 6 1/2 inch kickpanel Ford speakers do not need bass blockers installed, and Ford of course did not provide them. Does this help?Riddle me this...As a former Audio engineer manager, doesn't Ford have a crossover with the dash panel speakers and kick panel speakers eliminating the need for bass blockers?