pullin my hair out

[Karkov]

Subs up, port back IMO

2007 Tahoe here, daily ground pounder.

[MrSkippyJ]

10 cubes for 2 18s?

[ShadeTreeMechanic]

I run subs back port back and my tailgate hates it. Ten cubes is on the small side but will help them take more power and will have a flatter output. The port area sounds good and I know it can be hard to get enough and keep it in the box.

[quick65]

here are some pictures like someone asked for. it shows my starting point, with only like 40 miles on the Tahoe, I pulled the entire interior out and addressed it. i started with (3) 13w7AE facing back. that wasn't enough. then i tried (6) 13w7AE's, that wasn't deep enough, although was very musical. then i tried (2) zv418's faced up. that was plenty deep, but cooked one of the coils. then Jacob at sundown replaced both of my 18's for a custom set of 18's. he even autographed the dust caps, so i tried them in the same sundown spec box. they sound decent. i wanted more. so i tried a 4th order, wasn't musical at all. then i tried a wall, it got rid of quarter panel flex, but is down 3db from the sundown spec box. so my plan was to build another traditional 3rd order and was just curious if i might get better output if i kept the subs as well as the ports loading off of the back hatch. i did some browsing on this site but it seemed that most of the tahoes were running 4 drivers, so it was impossible to know if they chose subs up vs subs back, because subs back isn't even an option when running (4) 18's. so what i'm getting at is, i have done a fair share of experimenting and post-searching on my own before asking for advice. it's just that my table saw is starting to get tired of building boxes, for this car at least, and i was just hoping to hear some of your ideas as to sub-up or sub-back. in my mind i realize that 150db off of the rear hatch is probably gonna invite subtle nuances from the hatch itself, although 150db facing the roof had me worried about the roof taking on the shape of a volkswagon bug. considering i only have 20k miles on my truck, I'm a bit reluctant to install the equivalent of a jungle gym to reinforce shit.

as far as the net volume of the enclosure... i realize they suggest 7cu ft per driver. but after modeling it on winisd and achieving a fairly accurate graph of the sound that was actually playing, i started adjusting net volume numbers within the program to see what type of effect it produced. my findings: little to no desireable effect when using anywhere between 4 and 8 cubic feet per driver. if anything, the output just got peakier (is that even a word?) and that was not what i was after. if i wanted peakier, the fourth order was about as peaky as anyone might like. but i didn't care for the 4th order, although it might have made life easier in that i could have deleted every song on my device and simply rocked a 40hz test tone as my "playlist".

in any case, i truly appreciate EVERYONE's time who has taken the time to respond. you guys rock! CHEERS!

[Karkov]

10 cubes for 2 18s?

I did 20 cubes for 2 -18" when i ran Kicker Solo X 18's

[rocking.that.eclipse]

Subs up port back will yield you the best output in my opinion

[Joe X]

here are some pictures like someone asked for. it shows my starting point, with only like 40 miles on the Tahoe, I pulled the entire interior out and addressed it. i started with (3) 13w7AE facing back. that wasn't enough. then i tried (6) 13w7AE's, that wasn't deep enough, although was very musical. then i tried (2) zv418's faced up. that was plenty deep, but cooked one of the coils. then Jacob at sundown replaced both of my 18's for a custom set of 18's. he even autographed the dust caps, so i tried them in the same sundown spec box. they sound decent. i wanted more. so i tried a 4th order, wasn't musical at all. then i tried a wall, it got rid of quarter panel flex, but is down 3db from the sundown spec box. so my plan was to build another traditional 3rd order and was just curious if i might get better output if i kept the subs as well as the ports loading off of the back hatch. i did some browsing on this site but it seemed that most of the tahoes were running 4 drivers, so it was impossible to know if they chose subs up vs subs back, because subs back isn't even an option when running (4) 18's. so what i'm getting at is, i have done a fair share of experimenting and post-searching on my own before asking for advice. it's just that my table saw is starting to get tired of building boxes, for this car at least, and i was just hoping to hear some of your ideas as to sub-up or sub-back. in my mind i realize that 150db off of the rear hatch is probably gonna invite subtle nuances from the hatch itself, although 150db facing the roof had me worried about the roof taking on the shape of a volkswagon bug. considering i only have 20k miles on my truck, I'm a bit reluctant to install the equivalent of a jungle gym to reinforce shit.

as far as the net volume of the enclosure... i realize they suggest 7cu ft per driver. but after modeling it on winisd and achieving a fairly accurate graph of the sound that was actually playing, i started adjusting net volume numbers within the program to see what type of effect it produced. my findings: little to no desireable effect when using anywhere between 4 and 8 cubic feet per driver. if anything, the output just got peakier (is that even a word?) and that was not what i was after. if i wanted peakier, the fourth order was about as peaky as anyone might like. but i didn't care for the 4th order, although it might have made life easier in that i could have deleted every song on my device and simply rocked a 40hz test tone as my "playlist".

in any case, i truly appreciate EVERYONE's time who has taken the time to respond. you guys rock! CHEERS!

You show a lot but not much that I can find really useful. the sundown box for the 18s you liked is the one I likely know how you did and I suspect that you liked it mainly because sundown suggests pretty decent boxes for their drivers, if you did the JL boxes on the manufacturer specs I wouldn't be surprised you got a not too loud flatter performance, I can't see your finished 4th order box or wall nor detailed specs of them, if your wall is not properly sealed you can lose a lot of output, improper port area, box size, etc can also ruin a setup, how you aim your drivers and port is just one other thing to consider rather than your only / main problem.

[quick65]

eric cole who is an engineer at jl helped me directly in coming up with the jl enclosures. and i'm not sure what you mean by "likely know how you did"? the box is directly off of their website located under my driver's specific page. then i consulted with jacob fuller specifically prior to building it. the fourth order specs came from the amount of airspace i could manage to get while utilizing two enclosures and a front facia to give the appearance of a wall. so no, it's not sealed to the sides, although it is about within an eigth of an inch of the body panels allowing for vehicle shift encountered whilst driving. don't forget, it's a transportation vehicle, not built like a drag car. and yes i realize that "built like a drag car would yield favorable results, but i'm only after a reasonable results. i don't think 150db from two 18" drivers when using 6kw is unatainable without reinforciing the chassis, isn't it?

[Keith77]

This is what I would do...

Subs up port back (been proven to be the best for SUV's) Build the box on the larger side then its much easier shrink the box then add..

Make a removable port so you can swap different ports out.

Sounds like you need to test test test test test test until you find what you want.

I also think you are giving those X's way to much power

Hell Maybe try a different driver all together.. Tons of other brands

[quick65]

You show a lot but not much that I can find really useful. the sundown box for the 18s you liked is the one I likely know how you did and I suspect that you liked it mainly because sundown suggests pretty decent boxes for their drivers, if you did the JL boxes on the manufacturer specs I wouldn't be surprised you got a not too loud flatter performance, I can't see your finished 4th order box or wall nor detailed specs of them, if your wall is not properly sealed you can lose a lot of output, improper port area, box size, etc can also ruin a setup, how you aim your drivers and port is just one other thing to consider rather than your only / main problem.

I have yet to identify "my only/main problem." but feel free to offer your diagnoses. port area on the 3rd order was 200", and on the wall I am using 92.5" per driver. the main thing that is confusing me is how can my wall be 3db quieter than the ported box. the wall effectively cuts my cabin airspace in half and should therefore be a lot easier to get sound pressure out of. the only thing the subs up port back had going for it was that it was loading the port off of the rear hatch, but can that be enough to equal a 3db gain? I thought 3db was the equivalent of doubling the current amount of cone area. well the loading off the rear hatch certainly cant be responsible for adding the equivalent pressure of two additional 18" driver's can it?