Help with tuning aero ports

[KillerKeller40]

So I have never played around with aero ports and I need some help figuring out what size ports I need to get a lower tune out of my box. It is 3 cubes (14h x 28w x 15.5 d inside dimensions) with two 4in wide by 6in deep ports. It’s currently tuned to 36hz. I have a sundown X-10v1 on a twisted sounds 3.5k at 2ohms so 1,200-1,500 watts maybe. It does not hit lows at all is my problem. It’s very peaky between 40-60 hz. I’ve done my research and I’m thinking I need to go with two 4in by 10in deep ports to get 30hz but I could be wrong. So I’m asking for help guys. I’ll put a link to the box I purchased. Please guys help me out. 

Link to the box: 

https://www.amazon.com/OBCON-Single-Hidden-Chamber-Hatchback/dp/B001PBPI5A

also if anyone could explain the whole “hidden chamber” thing that would be great lol. 

[Mr DeeBeez]

I have never heard of a "hidden chamber box". When looking it up, the only thing about them that I could find was this box. And in the description of this box it says "Let me tell you a little bit. This box is special because of its propietary design we are not willing to elaborate on the design to much." 

1) The grammar mistakes in the product description would be a red flag to me

2) When putting the box specs in a box calculator, I come up with:

                     - 3.43 ft net, tuned to 44hz, with 7.33 square inches of port per cube. It has an estimated bandwidth of 33hz-88hz

That would be the reason you are not having a lot of low end response. The tuning is pretty high, cubic feet is way big for a single 10", and there is very little port area. I am not sure if the "Hidden Chamber" makes it not act like a typical aero ported enclosure, but the specs seem like a very poor match for the sub you are using. 

[KillerKeller40]

The whole hidden chamber thing I guess is because on the inside of the box it has an L shaped bracing as if it was going to lead to a slot port on the right side but it leads to an aero port. Kind of weird never seen it before. I know the box wasn't going to be perfect for the X-10 I know they can deal with boxes bigger then normal but not twice the recommended size, so it was a temporary box. I just got stationed in a new town and I don't know anyone out here to help me build a box, all the local audio shops just use all prefab boxes, so there was no help from them. Once I get settled in and hopefully find the car audio crowd out here in Abilene, Texas I plan on building a custom box.

Now on the tuning end of it its more of a learning/ experiment for me. I want to tune it lower to get more a of a low end response, being an aero port box I just need to figure out what size ports I need. from the numbers I ran I came up with two 4x10 ports but I could be completely wrong.

[Mr DeeBeez]

Based off of the box calculator I am using. Making the ports 10" long vs 6" long would only drop the tuning down to about 39hz. You dont really have a whole lot of room inside your box to make a very long port, and I dont know how much room you have in your trunk area, but If you make a 17" long port, and have about 7" of that port stick out of your box, your tuning should be right around 32hz. That would help out your lower end considerably, and give you a much wider bandwidth

[KillerKeller40]

I have a focus st hatchback so I have room to stick the port out. So Ima need two 4” wide by 17” long ports to drop the tuning to 32hz. Also I should have mentioned this before I have an LC2i installed as well it’s the new one with the built in distortion detector . I also tuned everything in my system with a DD-1.

Excuse the mess of my system I did it the other night from like 10-2am. I’m going to go back through it this weekend and clean it up. 

[Mr DeeBeez]

Here are the calculations I came up with. I extended each dimension by 1.5" since you said the dimensions you gave were the inner dimensions. So two 17" 4" ports should get you a much better tuning.  It is still on the small side for port area. So you may hear some port noise. But should sound better than it currently does. 

[KillerKeller40]

Would I be better off making the ports 18-20 inches long. I don’t care if they stick out of the box. I think it looks cool. 32hz would be great. This evening I’ll do some investigating on the box and see if I can cut bigger holes and maybe go with a 6” port. Thank you so much for your help. 

[Mr DeeBeez]

I would not do 2 6" ports. It would be quite large for your set up, and tuning would actually increase. you would need two 50 inch long 6" ports to get the tuning. Not practical, and Would not be anything better than what you have now. Your best bet is to stick with 4" ports. 

If you do 20" long 4" ports, with 10" of each port sticking out of the box, your tuning would be around 30hz. I personally wouldn't tune lower than 32ish, but that is your call. would be much better than the high 40's its tuned to now. 

Let me know how it goes, or if you have any more questions. 

[KillerKeller40]

I was only suggesting the 6" ports or longer ports to try and cut down on port noise but ill do the 4"x17" and also double check the measurements and try and do some more research on the box because the company swears its tuned to 36hz and is 3cubic feet but I don't see how that's possible. If I find anything different I will post it up.

[KillerKeller40]

So I just measured the external measurements of the box and they are 28w X 15.5d X 13h so with displacement and port area I’m guessing 1.833 ish. So that changes a lot. Glad I double checked first.