Slot port length difference between Torres and Carstereo.com calculators?

[osiris10012]

Hello everyone. I am redesigning my enclosure for my 15" ethos for different mounting options. I have done my research and this sub needs a total port area of 75 in2 in a 3 cu ft net enclosure. Now when I use the Torres calculator I am using the total net feature with 3 cu ft and also 3 common walls since it is a slot port. Using a port that is 4x18.5 at 56" long gives me a tuning of 31.94 hz and 74 in2 of port. Then when I use the same size port in the carstereo.com calculator it tells me 48.5" of length is required to give me 32hz tuning. So my question is which one should I use. In sketch up I am designing the port by measuring down the center. Thank you in advance for the help.

[Triticum Agricolam]

As far as I know Torres doesn't take end correction into account for 3 common wall slot ports. This is why it gives you a longer length. When I design ports I use the JL Audio formula with end correction. Based on the specs you listed I get a port length of 46.5", so pretty close to what carstereo.com gave you.

Port tuning is influenced by a lot of different factors, not all of which can be accounted for in the formulas, which is why none of them are perfect. The JL Audio one I use seems to get my pretty close most of the time.

[Joe X]

Torres does factor in the effective length for slot ports with common walls (the program also subtracts the volume of the end correction from the net volume), you can tell in the formula he drew below, in the car stereo com calc you are responsible to get the real net volume on your own while Torres miscalculates port displacement, sometimes by little others by more than a little. Also both calcs use different tuning formulas.

OP below 3Hz you don't need to be overly concerned unless you are doing one of those peaky scoring setups, those guys tune manually and on instruments.

[osiris10012]

Thanks for the input. I am not trying to tune for a peaky set up. My goal is a nice flat response. At the end of the day I just want to build a nice 3 cu ft net vented enclosure tuned to 32hz. Lol. After building my current enclosure I realized my original mounting plans weren't going to work. I want to get the port area higher from 60 in2 to the 75in2. I also want to make the net volume as close to the 3 cu ft as possible. Although my enclosure isn't much larger I feel it is a bit to big for the ethos.