Hi all! been lurking here for quite some time now, LOTS of great info here and seems to be a lot of knowledgeable guys/gals. Im a member on tons of other forums, mostly motorcycle stuff...
anyhow, here is my dilemma.
ive got an 06 dodge ram quad cab, there arent many options for adding bass to this truck due to the space available. Prefab i can use a hotbox between the center seats or some small MDF stuff under the rear. The prefab stuff thats made to go under the rear seat doesnt take advantage of all the available space and really limit me in sub choices.
my box now is a prefab and its right around 1.25-ft3, stuffed with polyfill it should be around 1.5. im running 2 punch 12's sealed, pushed by a kicker zx400.1 running @ 2ohma. the subs should have .85 each, needless to say its not bad but i want more...lol
my solution... fiberglass... i made a mold of the floor under the rear seats and have been working on finishing the box up. The extra space (cu.ft.) that i got from going this route is pretty significant. With some rough measurements the other night im looking at ending up around 2.25-ft3 gross, maybe a bit more depending on how i finish the top of the box and if i decide to shim the rear seat up some.
this is leading me towards a single JL 12 or 13 W6v2 in a ported box. The mounting depth on the 13 may lead me towards the 12. Ive always used sealed stuff in the past and thought id mix things up a bit and go ported this time...
my dilema is the porting the box. the box designs on jl's site call for slot porting, the way this box is made there is just no way to get a slot to fit so im going to need to go with round ports.
I called up JL and asked them and they told me to go with 2 4" ports at around 27" (depending of final volume of the box). If i go to a port calculator site i can tune the box to around 32 hz with a single 4" port thats much shorter. JL recommended the 2 4" ports to keep the same volume of air in the ports that they have in the slots in there design.
my question is, is the volume of air IN the ports have to be the same as whats shown in there slot in order to acheive good sound? I mean if i can tune the box to 32hz with a single 4" port at a shorter length, do i need to use the 2 LONG 4" ports they recommend?
what do you guys think/recommend?
ive never built a ported box before and never realized that the actual volume of air INSIDE the port was that big of a deal?
Thanks for the help! sorry for the long rant...lol if you need anymore info give a shout.
you have room for a 4" round port, but cannot slot port it? you know a slot port can be 4" x 4" right? or 5 x2 or 6x1 or 37000 x 1/2 or or or or or or or or or or or or or hence the nice thing about them.
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used to be loud, used to be fast...now I am married LOL
ibasspro wrote:
you have room for a 4" round port, but cannot slot port it? you know a slot port can be 4" x 4" right? or 5 x2 or 6x1 or 37000 x 1/2 or or or or or or or or or or or or or hence the nice thing about them.
i dont have room for the length of run that they want to use. unless i want to put a ton of bends in it.
that and im not that good at coming up with this stuff...lol
You have to look at the port opening size in square inches. JL has figured the minimum square inches of opening space that will allow the box to perform with full allowable power without noticeable "chuffing" sounds coming from the port. If you intend to power the sub anywhere close to its potential, you will need to allow that much port opening.
The actual dimensions of the port opening can be changed, such as: a 12.5" X 1.5" can be changed to 5.75" X 3.25", or to a round port that is ~5" inside diameter (square inches remain about the same), and the length of the port does not change from spec. You are still allowing enough port opening to eliminate unwanted port noise, and are allowing the proper port length per port opening space for desired Fb in that amount of net airspace. But, if you reduce the opening square inches (especially by half!) for the purpose of getting a shorter and more manageable port length, you introduce the real probability that port noise will interfere with your sub system sound.
Your case, in particular, does not lend itself to taking the easy way out and making the port smaller so that the length will fit into the space. Your sub is in the cab next to you, not back in a sedan trunk where port noise may not be as noticeable. You have to abide by the specs if you want to vent that sub.
Look into using the sub in a sealed box for your application. Both of those subs are designed for best performance in sealed anyway.
For additional info, use the forum search to find: pi r^2, fs/qes, qts, ebp, and those particular subs you have in mind. The 12volt.com Google search tool near the top right side of the main site page is a great search engine.
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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
i really appreciate the feedback! i followed some of the links and im already gaining a much better understanding.
i have some more reading to do yet though. im going to end up with more ft3 than JL is recommending for the 13(1.875), and i'll have around 2.25 ft3 after deducting the sub and ports.
the few reviews ive found, guys have been happier with a larger than spec box. from what i understand so far a bigger box will make the sub more efficent and able to go lower easier? i was considering some polyfill as well and need to find out if i should factor in the polyfill into finding my port length when plugging in my box volume.