Contour Enthusiasts Group Archives Forums Modifications Audio dnewma04, this grasshopper needs to learn

I need help on getting the cu. ft. for a box with 4 dimension. Actually before I get into that I am planning on putting in 2 15" kicker xpl's and powering them will be a jbl 1200.1 amp. which I found at etronics.com to be the cheapest, 309.99 for the 1200.1. The speaker thermal power handling is 600 watts each and there max on an enclosure is 2.7 cu. ft. the box that I plan to put them in is 37.5w x 18h x 19d1 x 12d2 and that is external. The wood being used is all mdf 3/4(heavy!!! there goes my gas mileage) It also has a center divider. so how do I get the cu. ft. from this box and if the box comes out being to big, would factoring in the speaker displacement make a difference? Thanks for the help in advance.

The easiest way to figure the cu ft is to take the two depths and find the average. In this case, (19+12)/2=15.5. Now take that 15.5x37.5x18/1728 and that will be your cubic ft. If that was your external box dimensions, then your internatl dimensions would be 14x35.25x16.5.

You can normally figure that a speaker will take up 10% of a normal sealed enclosure. Also, keep in mind that sealed enclosures are very tolerant to over and undersized boxes.

Ok, cool got it. So let me make sure that I am getting the rest of the process correct. Now I just times 14x 35.25x 16.5 =8142.75 then divide 8142.75 into 1728 which equals 4.71 and then divide 4.71 by 2 =2.3 cu. ft. . Is that correct. One more thing that I forgot to mention. should I use polyfill? if i do it says on the instructions to only use 50% poly fill now is that having 50% of the cu.ft. filled?It really does not specify to go by what. So should I go by 1lb. per cu. ft.?

Ok, cool got it. So let me make sure that I am getting the rest of the process correct. Now I just times 14x 35.25x 16.5 =8142.75 then divide 8142.75 into 1728 which equals 4.71 and then divide 4.71 by 2 =2.3 cu. ft. . Is that correct. One more thing that I forgot to mention. should I use polyfill? if i do it says on the instructions to only use 50% poly fill now is that having 50% of the cu.ft. filled?It really does not specify to go by what. So should I go by 1lb. per cu. ft.?

Yes, you should use polyfill. It'll make the apparent volume seem larger to the speaker. I can
't remember off hand about the polyfill, but i recall there is some weight per cu ft that is considered 100% fill. I'll check into it.