buff_n3rd Posted March 26, 2016 Report Posted March 26, 2016 Hoping I ask this hypothetical question correctly. If i had a 12" sub that required 1 cubic foot of air and a 4" x 4" square port that is 12" long tuned to 35hz and decided I wanted a second 12" sub (exact same sub) and doubled the volume of the box to 2 cubic feet, does the port need to also double or does it stay constant as long as volume is correct for the woofer? Seems like some online calculators ask for speaker qty and others don't.
Broke_Audio_Addict Posted March 26, 2016 Report Posted March 26, 2016 The port would have to increase in size as well. That being said a lot of people's definition of "music" is a clipped 30 hz sine wave with some 80 IQ knuckle head grunting about committing crimes and his genitals.
buff_n3rd Posted March 26, 2016 Author Report Posted March 26, 2016 Good to know and that is what I'm most worried about on my current build. How much port area or port length would I need for 4 x sundown x6.5? My port size is 5 x 3.5 and worried I calculated length wrong (that's what she said).
buff_n3rd Posted March 26, 2016 Author Report Posted March 26, 2016 I completely realized after the fact that the question can't be answered without box volume. Right now my net volume is 1.28 cubic feet.
MotorCityFats13 Posted March 26, 2016 Report Posted March 26, 2016 I completely realized after the fact that the question can't be answered without box volume. Right now my net volume is 1.28 cubic feet. length is also dependent on tune are you still going for 35hz and did you mean gross volume because you cant have a net volume without the port figured in... 5 x 3.5 x 26.5" long for a 35hz tune and the gross volume would have to be 1.76 not figuring in sub displacement to achieve the 1.28 net volume if you already have a box that is 1.28cuft then that port will never be able to get you to 35hz because as the port gets longer so does the port displacement changing the tune and then again impacting the volume so you will never be able to drop the tune lower than 44hz-ish always build a box around the port never build a box and port it later
buff_n3rd Posted March 26, 2016 Author Report Posted March 26, 2016 I meant net only because I was building backwards in my head. Current box is scheduled to be 1.78 cf minus displacement of subs which is .2 for 1.58 cf. Minus the external port dimensions which is .3 for a net of 1.28.
MotorCityFats13 Posted March 26, 2016 Report Posted March 26, 2016 I meant net only because I was building backwards in my head. Current box is scheduled to be 1.78 cf minus displacement of subs which is .2 for 1.58 cf. Minus the external port dimensions which is .3 for a net of 1.28. then this math would be spot on "5 x 3.5 x 26.5" long for a 35hz tune and the gross volume would have to be 1.76 not figuring in sub displacement to achieve the 1.28 net volume" and you said external port? if you really meant external then you don't subtract this from the displacement but if you meant internal port then the math I listed is spot on to what you mentioned in the last post
buff_n3rd Posted March 26, 2016 Author Report Posted March 26, 2016 It's internal but I was treating the port volume outside of the necessary volume otherwise every change to the port volume would change the internal volume and it would be a back and forth until they match up correctly.
buff_n3rd Posted March 26, 2016 Author Report Posted March 26, 2016 This is what I currently have sketched up. Hopefully it shows because in linking from my phone. https://drive.google.com/file/d/0BzExFfp4AGn4bmtUWVVwNXpnMGc/view?usp=docslist_api https://drive.google.com/file/d/0BzExFfp4AGn4b1RUTUdtOUxzN0E/view?usp=docslist_api
buff_n3rd Posted March 26, 2016 Author Report Posted March 26, 2016 https://drive.google.com/file/d/0BzExFfp4AGn4dkVlSGdsdEtuUmM/view?usp=docslist_api
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