box tuning help

[Aj11]

I'm building a 7 cubic foot box for my 2 type r 12s. i want to tune it for 30hz. i can easily tune it by adding a 8inch diameter pipe at 11inches long. but i was reading that if the port Is 80% the Size of the cone its better for air flow. so i want to add 2 8inch diameter ports. but i don't know how long i should make each port! i will flare the ends for less turbulence the ends will be as close to 9.2 inches as i can. heres my box layout 48w 16h and 19.44d please any help is greatly appreciated. I'm not so good at math so If you could just tell me how long each 8inch port should be that would be amazing. first Post here be gentile

[truthsayer]

here is the link for you http://www.psp-inc.com/tools.html it simple and easy.

[CleanSierra]

Right around 18.5" should put you on that tuning with the GROSS airspace. The subs displace a little, probably .28-.34ish. Assume .34, your net space would drop to 6.66(yikes) making the ports about a full inch longer. I didn't plug that info to Torres or anything there's a chance I missed some displacement somewhere. I feel like I'm probably pretty close.

[Aj11]

two questions, 1. why is the length different from my other tuning app for the single 8inch diameter. and 2 it says for 2 ports flared it should be 35.6 inches long. is that each port or do i cut that in half and make each port 17.8 inches?

[CleanSierra]

I'm guessing it's doubling the length because there are two ports. Let me check. I can't get the tuning correct either with the volume the port displaces. I don't believe the PSP calculator takes that into effect. 2 6" aeros comes out to 31.25Hz at 20" length. Maybe that's an idea. I don't think you need twin 8" ports for two Type Rs. That would be like 50" of port per sub :/

[truthsayer]

two questions, 1. why is the length different from my other tuning app for the single 8inch diameter. and 2 it says for 2 ports flared it should be 35.6 inches long. is that each port or do i cut that in half and make each port 17.8 inches?

The psp calculator factors in port displacement. But you should factor in sub displacement before entering cu-value. 1 flared port is16.6'', if not useing a flared port it would be 15.6'', and if useing 2 ports each port would be 38.15'' if not flared subtract 1''. Just make sure you factor in the sub displacement so you get the correct volume.

[Aj11]

they will be magnets out. always liked the look and easier to design. so you guys think 1 8inch flared port at 18.5 inches would be just fine? i plan on doing magnets out and up with the port facing my tailgate. 99Durango. so you would see the magnets threw the rearview mirror and you would only see the port when you opened the tailgate

[Guest]

wait why in the world are you building a 7 cube box for 2 12's?!?! thats fucking gigantic. thats 2 15's territory.

[Aj11]

i was talking to a guy on make it louder com and he said they could handle it. i was gonna do a 5ft box but he said the new rs would be fine. each sub has it's own jl 500/1 v2 on 00gauge wire to a 1in 2out distribution block with 4gauge out. same reverse for the ground wires.

if you guys have any other ideas please feel free. this Is my first box build so I'm nervous and excited at the same time. right now ihave a atrend kandy kolor box i spent $260 on and i f'en hate it! what a waste of money!

[Guest]

LOL. no 12s like 3.5 cubes a piece. thats just absurd. the power handling of the woofers will go WAY down. and you'll be able to bottom them out much easier.