deadbroke Posted August 3, 2016 Report Share Posted August 3, 2016 I built the majority of my box for 2 15s in a bandpass blow through 4th order but i am still deciding how big to make the port since space is limited due to contours in my truck bed. The current volume is 3 cubes sealed for each sub and 12.5 cubes for the ported area. Both values are net after bracing displacement. The only part i have left if to screw on the face of the box and attach the port to it. The curent opening for the face of the box is 16 x 47 but with the amount of truck bed height and molding on front of the truck bed i can do a port opening of 11 x 44. From the bed into the cab it looks like about 4 inches of length minimum for a port. I tried running a calculator for bandpass it gave me about 595 inches for minimum port area assuming 45 hz i wont be able to make that so if someone could help calculate a good frequency and port size and length that would be great Link to comment Share on other sites More sharing options...
Triticum Agricolam Posted August 4, 2016 Report Share Posted August 4, 2016 What amp are you going to use? "Nothing prevents people from knowing the truth more than the belief they already know it.""Making bass is easy, making music is the hard part."Builds: Link to comment Share on other sites More sharing options...
diegoclass2010 Posted August 4, 2016 Report Share Posted August 4, 2016 that's a big whole you cut out. i would do anywhere from 180 to 220 square inches of port for 2 15's.. try this 20" width x 11"height x 14" inches long should be around 45hz tune with around 11 cubic feet net Link to comment Share on other sites More sharing options...
deadbroke Posted August 4, 2016 Author Report Share Posted August 4, 2016 So ill be using a rockford t4000.1 for the pair a little over 2000 a sub. I didn't cut out the face of the box yet i just haven't screwed it on yet. I was curious about the length of the port i read a few places to try and keep the port short i think for noise issues is 14 inches pretty standard for bandpass boxes all the ones i have seen looked relatively short Link to comment Share on other sites More sharing options...
Triticum Agricolam Posted August 4, 2016 Report Share Posted August 4, 2016 On 4000 watts you are going to want to have around 200 - 240 sq in of port area. Diego's recommendation is good. I would suggest making the port removeable so you can tweek the tuning frequency if needed. "Nothing prevents people from knowing the truth more than the belief they already know it.""Making bass is easy, making music is the hard part."Builds: Link to comment Share on other sites More sharing options...
deadbroke Posted August 4, 2016 Author Report Share Posted August 4, 2016 I figured the port would be fairly short but at least i have a starting point. So with a 14 inch port is that assuming about 10 inches of the port is inside the box offsetting my ported net side to 11 cubes? I should have figured port size before i made the box so i could keep my ratio at 2 to 1, if it matters that much with 1^3. I planned to make a removable port but if i wanted to change the frequency would i have to make the port area bigger or just change the length of the port? Just trying to avoid cutting the bed and cab to fit the port more than once. Thanks guys Link to comment Share on other sites More sharing options...
Triticum Agricolam Posted August 4, 2016 Report Share Posted August 4, 2016 To change the tuning frequency you would leave the port area the same and just change port length. FYI, ratios are pretty much meaningless, if anything your front chamber is on the large side of things. You may end up with a pretty big peak in output because of this. "Nothing prevents people from knowing the truth more than the belief they already know it.""Making bass is easy, making music is the hard part."Builds: Link to comment Share on other sites More sharing options...
deadbroke Posted August 4, 2016 Author Report Share Posted August 4, 2016 Sweet so i would just change the length. Doing the numbers here if i leave about 10 inches of port in the box and 4 outside to get 14 inches i would displace about 1.3 cubes in the box. Now if i change the length of the port i would have to modify it outside the box because if i change the port inside it would change volume right or would that not have much of an impact? Link to comment Share on other sites More sharing options...
Triticum Agricolam Posted August 4, 2016 Report Share Posted August 4, 2016 You can just modify the part that's inside the box. Changing the length of the port inside the box isn't going to make a big enough difference in chamber volume to really worry about. "Nothing prevents people from knowing the truth more than the belief they already know it.""Making bass is easy, making music is the hard part."Builds: Link to comment Share on other sites More sharing options...
deadbroke Posted August 5, 2016 Author Report Share Posted August 5, 2016 Alright then it's settled I'll start building the port tomorrow thanks guys for the help! Link to comment Share on other sites More sharing options...
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