Advice on a box and removable port design

[Woofer Pressure]

Hello, this is my first post on this forum and I was hoping to get some advice on a box and removable port that I designed.

The box will hold 2 Sundown SA12's and is 4 cubic feet after port and sub displacement. I haven't decided on an amplifier yet, but it will probably be around 1500 watts RMS. The box will be going in the trunk of a 2000 Acura Integra hatchback with the subs and port firing towards the rear.

Here is a shot of the rough 3D SketchUp model I designed:

This shows the inside of the box with the top removed:

My first question is whether the angles in the box behind the sub magnet will negatively influence the sound in any way?

I also have designed a removable port that looks like this:

Here is a top down view of the port opened up so you can see the port direction:

The depth of the box does not allow for the length or port that I need so I designed this port that makes a 180 degree turn to allow for more length. Does this look like a feasible design?

All of these 3D models are rough drafts and the final box will have all edges rounded to allow for smoother airflow and will also have bracing. This is my first box build so any input would be greatly appreciated. Thank you!

[REH]

I forsee JoeX and Triticum shining some knowledge on this for you. Both of those guys know what seems to be everything you could possibly know about enclosures and ports. Interested to see what they say about the 180 port turns though.

[Triticum Agricolam]

The angles behind the motors aren't anything I'd be concerned about, if anything they should help.

Your port design is pretty interesting. With any port you want to maximize air flow into and out of the enclosure. With this in mind I normally try to avoid 180 degree turns, though sometimes this isn't possible. I've had several successful designs with 180 degree turns, so they aren't the end of the world, you just want to be sure you have enough port area to keep your port velocities low. Air resistance increases by a factor of 4 for every doubling of velocity, so if you are able to keep your port velocities reasonable it really helps with less than ideal port configurations.

Other things you can do is roundover all edges that air will be flowing past. I also like to put 45 degree angled pieces in the port corners to help with air flow.

If you post a link to your SketchUp file I can tweak things a bit to show you how I would build it.

[Woofer Pressure]

I really appreciate the help! This is not a perfect 3D model by any means, but everything should be to the proper scale.

Here is a Dropbox link to the SketchUp file: https://www.dropbox.com/s/9ejygxmliqg4hsu/Subwoofer%20Enclosure.skp?dl=0

[Joe X]

Probably subs up will work better, on the port, it displaces a lot of net volume and unsure if you have proper clearance on the external end, maybe there will be simpler ways to do it. You should maybe post car's available space. BTW welcome.

[Woofer Pressure]

Probably subs up will work better, on the port, it displaces a lot of net volume and unsure if you have proper clearance on the external end, maybe there will be simpler ways to do it. You should maybe post car's available space. BTW welcome.

Thank you, it's good to be here.

The reason I did subs back is that it is just louder that way in my particular car. There is very little low end extension with my current subs pointing up as opposed to back. In regards to available space, this box design is basically the maximum amount I have to work with.

I agree that the port does take up a lot of volume but it was the only way I could think of doing it. It would be great to get some other creative port design ideas. My only criteria is that it be removable so the tuning can be changed.

[Woofer Pressure]

Thank you for the input so far. Any other thoughts? I modeled the box in WinISD and got a peak port velocity of almost 27 m/s which I believe is pretty high, and the 180 turn won't help either. Any other port designs you can think of that might work better?

[Triticum Agricolam]

I've been playing around with your Sketchup file a bit. I'm really busy and haven't had a chance to finish what I started, but if you give me a couple more days I'll post back with my suggested changes.

[swishahouse22]

all I can say is I had a friend that built a box with removable port and all he did was put scrap wood in it to make up for the displacement.

[Joe X]

Thank you for the input so far. Any other thoughts? I modeled the box in WinISD and got a peak port velocity of almost 27 m/s which I believe is pretty high, and the 180 turn won't help either. Any other port designs you can think of that might work better?

Use a different software and you will likely get a different peak airspeed so yeah, your area is around to what Sundown gives tuned to low 30 so you can't be so off, anyways I noticed a couple of things with your port, 1- the total area of the internal end is lesser than the one on the external end, that's not standard ported for it to be, both total areas should be equal, 2 - your box is almost 29" and your port is 6 wide, minimum external clearance would be 6" soo you have that?? The following is a pic showing what a standard port would look like and proper areas and external clearance shown: