6th Order C-Pillar Or Slot Ported Box?

[malandrin4o8 10+ year member]

I have 2 custom 18” Subs that are rated at 3500rms with 4” voice coils, big roll cone. I have them on a taramps md8000, 96ah lithium, dual alternator with its own 300amp alternator just for bass. Installed in a 2003 Yukon Denali.

My current box came apart from either poorly built or too much pressure. It was dual 3/4” mdf all around with a triple baffle. Subs up port back about 5” from tailgate. These where the box specs 9.49 cubes tuned at 27.31hz ( tuned too low for my likings) with 135in port area box was originally for 2 15s.

I’m looking to build a new box but undecided if I wanna do another conventional box or go with a 6th order C-pillar. I don’t compete at shows but I want a daily musical pounder( couple trucks in my area that are loud). What are y’all’s suggestions? Any input is appreciated. Thanks in advance.

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[Popwarhomie 5,000+ posts]

9 cubes is small for two 18s. Do you have the space to go larger without going wall?

I have had more walled setups than no wall but if I had the space I would take a no wall setup.

 

[malandrin4o8 10+ year member]

9 cubes is small for two 18s. Do you have the space to go larger without going wall?

I have had more walled setups than no wall but if I had the space I would take a no wall setup.

Yes I have more room, only used that box bc I had my 15s in it and didn’t want to build a new box at the time. My max dimension I have are 49”W x 36”D ( leaves about 5” from hatch )x 35” H. I have a rear view camera mirror so back window blockage is not a concern.

 

[Jason9835]

Yes I have more room, only used that box bc I had my 15s in it and didn’t want to build a new box at the time. My max dimension I have are 49”W x 36”D ( leaves about 5” from hatch )x 35” H. I have a rear view camera mirror so back window blockage is not a concern.

I'll give it a shot. How about a slotted port design? What are your subs T/S params?

 

[Buck 5,000+ posts]

With that amount of power, you really need to make sure you have a proper box or else you'll never get all of what the woofers can do. If 27-ish hertz is too low for you I would consider ported or even a flat wall ported; keep in mind the 18s might have a really low FS as well, 4 inch voice coils tend to be pretty heavy. I'm not sure what your vehicle is but almost always 2 18s with 3500 watts per is plenty of power to do a flat wall. Really there's a lot of style of boxes you can do, as long as they are done right. If I was designing that I might even do double layer box all around if you're only doing .75. You really need to make sure that box has great structural integrity, internal bracing. A lot of 18s need around six cubes of air space or so. There's some 18s that have been able to work in 4 cubes or so but that's rarer, my gut instinct would say usually 5.5 to 6 cubes would work but sometimes 18s can vary greatly. I've seen 18s that could also use 7-8+ cubes per speaker.

 

[Cee]

Ported all the way. Preferably a side port vs center.

 

[Doxquzme Premium Member]

Listen to Buck. You need a bigger, stronger box. As for the port, rule of thumb, best is on the baffle but not an absolute. Join a forum where the feature your vehicle (even the Ford Pinto has a forum) and see who did what and how the port location affected the outcome, but with big large drivers like that, they couple best on the same baffle and any other consideration would be how they load in the car.

GP audio just shipped me a 12 cu ft net (15.5 cu ft gross) box, a glue and screw box, tuned to 19hz for dual dayton 18" ultimax subs for my home theater, $600 to my door. Triple baffle (double mount and vanity) fully braced with 2 window braces and additional corner braces too. If you want to cut and make it yourself, IM me I'll provide the cut sheet.

You can shorten the port and raise the tuning frequency, that would be pretty easy to do. You will have to email them or call for specifics if you decide to have them cut it and ship it. If it had been going in a vehicle, probably would have shelled out another $150 fo Birch Ply, in the home, heavier is better.

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