soffit mounted speakers dimension question

hi all , im looking for the dimension's that will be the finished opening around my nearfield monitors( mackie 824's or krk v8's) is there any formula in which to configure such dimensions? ..........thanx in advance. :D :D :D

Well, in my design the baffle opening would just be the height and width of the speaker plus 6mm. Maybe I don't understand your question? Thomas

hi ,and thanx for your reply i guess that i should have asked how much bigger than the speaker should the opening for the speaker be? if thats what you thought i eant than what would the 6mm be in standard meas. ( would that be 3"?) thanx again for your time.......... :D

won't that affect the step response of the speaker? Andrew

Thomas answered your question correctly. Your conversion to inches, however, is off a bit - there are 25.4 mm in one inch, so Thomas is recommending that the hole in the flush mount (soffit) be 1/4" larger TOTAL in each dimension than the dimensions of the speaker box. That small a gap dimension won't affect lower frequencies at all, because it is such a small portion of a wavelength... Steve

sorry guys i just got back from vacation.thanx for all your help and wisdom . :D :D :D