View Full Version : Fi BL18 Ported Box Design Help

04-18-2014, 02:07 AM
Hello, all. For anyone who saw my other thread, thanks for all the help! My new questions do not relate to electrical, so I am making a new thread.

I am buying a BL18, all purty'd up. Getting Dual 2 Ohm(going to run both in parallel), Cooling option, and red logo. I am now designing a box for it, and need some help/advice. It will be amp'd by a ppi bk1800.1d.

I have 37(top)/44(bottom) depth X 17 height X 37 width to work with. I have a 2007 Monte Carlo LT, for the record. Is RE box calculator a reliable/good designer? I have been using it and most of my questions are based on what it has given me. The way my back seats are shaped, the wedge part of the depth would be facing the front of the vehicle. If this would adversely affect sound, then it will have to remain a square. I also have no easily available(that I know of) way of cutting angles, so maybe a square/rectangle box is for the best.

Since finding them on YouTube, I have been fascinated with hair tricks. I have been told to tune low, so was thinking of going at 30hz. I mostly listen to dubstep(Liquid Stranger, Excision, Bass Mekanik, etc.) but have a bit of everything from time to time. The way I understand it, I should be as close as possible to the top of the subs 5-8ft^3 range as well. If a hair trick is not possible on my system, then I would like to have a fairly even mix of volume and quality.

Due to size limitations, the woofer will need to face up, so I was thinking having 16 or 16.5 as the height, to avoid excursion issues(BL18 has 18mm). I was hoping to leave about .5 inches off per side to allow for wiggle room(not accounted for in numbers near start of post). I will want the port facing back for optimum volume, yes? And is there any type of port that is louder? I figure on slot since I have the space for it, and should it be a long thin slot on the bottom or a larger upright slot on one edge of the face? Another port question: Do I need to have a bend in it like RE has? This really lowers my cubic footage, which is lower than I'd like already.

Link to RE Box Calculator: RE AUDIO - Box Calculator (http://www.reaudio.com/box.php)

tl;dr I am getting a BL18, questions are as follows:
Is RE a good box designer?
Will a wedge with the "face" pointing forward with port facing back ruin sound?
Woofer has to face up. Is a rear facing port the loudest?
What type of port is better?
If slot, is it better long and thin or bigger and upright?
Whichever I go with, do I need a L-Turn in it like RE does?

04-18-2014, 03:45 AM
i've built a few boxes for the Fi BL18.


sounds like you will waste a lot of output in the trunk. note that maximum trunk dimensions are not equal to the size of box you can physically fit through the trunk opening.

wedges are great for boxes. you need a circular saw with adjustable blade angle and a straight edge - or a table saw.

bends in ports are not ideal but necessary to lower tuning. aim for ~70 sq. in. of port area. use a round-over bit on port edges (inside and out).

04-18-2014, 04:37 AM
What do you mean by wasting output on the trunk? Not quite following there. The opening is quite generous, at 42w X 21H. I will be making a mockup box out of a cheap material to make sure before I finalize anything. I estimated with a tape measure(all I had handy) and was able to keep it straight(sounds like I'm a retard but I promise if you'd been there you would give me some merit) If there is math for this that'd be cool. This is the first time I've used math I learned in school for things outside of school.

04-18-2014, 04:58 AM
Also I thought I wanted a lot of port area? I like to have lots of low end and lots of volume

04-19-2014, 05:05 AM
Would this work for a box design? That is max height in the "front of car area of trunk" in pink, trunk lip in blue, and preferred "tail light area of trunk"height in green(wanting woofer and port on same plane as per Fi's recommendation by their support guru.)
The face(black) will have to be wedged to achieve 19. I have 18-18.5 height to work with at that part of the trunk. Sub OD is 18.5. Or I could do woofer on top. In that case, I'd probably go rectangle for ease and fine tune my cuts.
Could someone tell me if this would work and help with calculations? I have no idea what type of math I would do for this. I have so far only used RE. Thanks

04-19-2014, 06:30 AM
If I were to d oa wedge, the "wedge"(green) part would be facing the back seats, with the sub mounted facing up and the port(red) facing the rear of the car. I was wondering if this would damage the sound or add more ft^3 in a beneficial way

04-19-2014, 06:43 AM
What about this? It gives me the size benefits and stays within my space limitations. Port still facing rear. This gets me 7.04 ft^3 after sub displacement, and 31.8Hz tuning(was hoping for 33-35 but close enough I think)