Box Design for Sundown X15 v2 D2

[MacCollins]

This is my first time posting on the forum and I'm very new to all things car audio. I've done lots of research but I keep running into the roadblock of what box design I should build. I have a Sundown X15 V2 paired with a Kicker 1200CX (I plan to upgrade this later it is just what I have at the moment so if you have any recommendations feel free to leave those as well). I am putting the box in the trunk of a 2021 Honda Accord Touring. I mainly listen to Rap Music with some EDM/Dubstep intermittently. I got the X15 as I was missing the low-frequency response that I desired in my old system. My main question is how I should design the box. I want a box that plays the lows well without being peaky and making the box as small as possible to maintain as much trunk space as I can. Any advice is appreciated so thanks ahead of time. 

[MacCollins]

I am beginning to go down the rabbit hole and learned about WinISD and began tweaking. I really liked the frequency graph at a 3.7 ft^3 volume tuned to 24 hz. This gave me the flattest curve I could find and seems to be like the right fit for me while keeping the space the box takes up to a bare minimum. 

Edited May 20 by MacCollins

[crispy_chick3n]

you are on the right track. you know where you want your box to be at, now you need to get a box calculator like torres box tuning calculator or the ultimate car audio app. from there you can input overall dimensions and port dimensions to try and get it to your specs from winisd. 

 

when i do it i usually start with my maximum dimensions and see where the cubic footage is at. if its within a cube or 2 ill input what i roughly want for a port and see where im at for cubic footage as well as tuning. from there its just a game to play with the dimensions to get what you want. 

 

please feel free to post up some screenshots of both the box calculator as well as winisd, and id be more than happy to help steer you in the right direction. 

 

ill be the first to say im not the greatest at design, but ive been doing it now for the better part of 15 years and ive got a decent grasp on at least what not to do. 

[MacCollins]

@crispy_chick3n I could not get the software that you mentioned to work, probably just my lack of knowledge on the subject but this is what I was able to come up with. I attached the EQ for the 24hz box with 3.7 ft^3 of internal volume as well as the Air Velocity for the size port I am using. I read that you should try to get close to 17 but I assume that 19 will be ok. Next, I took these values and put them into Sub Box Pro. This gave me a box with a vent sticking out the side, but I assume that I could add a second layer and it would work the same. (Please let me know if this isn't true) I did the calculations for how long the second layer would have to be while maintaining 3.59 inches of width throughout the port. Then I realized that this new port would decrease the internal volume, so I calculated the difference in volume and extended the front of the box accordingly. It needed an extra 2.97 of depth to be able to keep the 3.7 ft^3 of internal volume that I had in WinISD. I was worried about how this would affect the tuning but it seems like it would only lower it fractionally. I am pretty sure that this is calculating correctly. At the bottom of my scratch work you can see the finished dimensions from the top down. The height would be 18" so 16.5" internally as I am using 3/4 MDF for this project. I hope that I did this right as this is my first time doing anything like this but the math seems to check out. Any clarification or advice is seriously appreciated.

Edited May 20 by MacCollins

[MacCollins]

I'm going to tweak this some more to try to make it have a smaller footprint so I will post any updates I make as well. 

[crispy_chick3n]

this is what i get when i punch that box into torres. unless i got port length wrong, that bad boy is going to be tuned super low...

[crispy_chick3n]

my suggestion would be to bring that tuning up a bit. into the 32-35 hz range. youll gain more output in a usable band. tuning that low (in the low 20s) isnt really good for music. and hell even tuning in the low 30s could be argued not the best for music, but if you want it to reach down low and still be able to jam to some edm id suggest bringing the tuning up somewhere around what i have here

Edited May 21 by crispy_chick3n

[crispy_chick3n]

Just now, crispy_chick3n said:

my suggestion would be to bring that tuning up a bit. into the 32-35 hz range. youll gain more output in a usable band. tuning that low (in the low 20s) isnt really good for music. and hell even tuning in the low 30s could be argued not the best for music, but if you want it to reach down low and still be able to jam to some edm id suggest bringing the tuning up somewhere around what i have here

hell id honestly like a little more port area per foot, but this might be ok. just have to check port air velocity on winisd. goal is sub 30 m/s. lower is better, but under that and you are usually a-ok

[MacCollins]

@crispy_chick3nThe EQ that I attached was tuned at 24hz. So it looks like the calculations worked. Is it a bad thing to tune the box that low? I ran it through WinISD at 32hz tuning and didn't like the way it looked. Right now I have it in a box tuned by someone else so I am not 100% sure of the exact tuning but it is a little peaky and lacks the low lows that I am looking for. This is what the EQ looked like at 32hz. 

Edited May 21 by MacCollins

[MacCollins]

Oh sorry just saw your last post. Is the EQ that I attached above good? I didn't like the look of the hump at around 35 hz as it looks like it doubles in volume at that frequency. What is wrong with tuning a box that low? It looked as though the volume would be the same from 25hz all the way up which i thought was the goal but I could be 100% wrong. Thank you so much for all the help