Subwoofers facing opposite sides instead of same direction

[InfiniteRuckus]

I'm trying to design a box for 2 - 12" DC Audio Level 4's. The space is somewhat on the tight side (2 door Pontiac Grand Prix), so I was thinking about facing one left and one right instead of both in the same direction (forward) on the same sheet of wood. Something like pictured below.


I was also thinking a single 4" port for a roughly 3 cubic foot box (tuned around 45 hz). I'm not sure if 1 port would be sufficient or not. Originally I was going to use the trunk but I want access to the spare tire in case of emergency, so I'm pretty sure it's going in the back seat instead. I've never seen anyone face subwoofers towards opposite sides of a car before, so any problems you can think of, or feedback would be greatly appreciated. Thanks for your time.

[Triticum Agricolam]

Having the sub face opposite directions is a fairly common practice with home audio subs, its called dual opposed and it does have some advantages for that application. In a car I do see any reason why it wouldn't work. I would still try to keep the subs located as close to the rear of the vehicle as possible though.

You are going to need a LOT more than a single 4" port for that box, just how much more depends on how much power you are going to run. What amp do you plan to use?

45 hz tuning is also pretty high, do you have a particular reason for wanting to tune that high? Your low frequency output will suffer.

[Joe X]

Weird because in that vehicle usually there's space for two 12s facing the same side easy, anyways port area need to be like 35 square inches per driver for those L4s likely more at high tuning, anything above 37Hz tuning will not be that nice on rap music and such.

[InfiniteRuckus]

Thank you two for the replies.

You are going to need a LOT more than a single 4" port for that box, just how much more depends on how much power you are going to run. What amp do you plan to use?

45 hz tuning is also pretty high, do you have a particular reason for wanting to tune that high? Your low frequency output will suffer.

I forgot to mention the port I want to use is a round aeroport. The amp I was looking at is 1800 watts hifonics. I know I'll get bored with it at some point and upgrade to a Sundown 3000 and set the gain down to 2800 watts. That's also why I'm going with level 4's instead of level 3's.

The reason I was aiming between 40-45 because that was the most common frequency I found after plotting the spectrum of songs I like, using audacity. There were a few that dipped into the 26-37hz range for brief periods (like Gucci Mane - Watch Cost a Bentley). I still want to hear those regardless of how brief. Would a 40hz tune basically cut those out? If so, I'll reconsider 36-38hz. I've been listening to a lot of high energy trap lately, which I've found peaks & sweeps between 40-70hz.

Weird because in that vehicle usually there's space for two 12s facing the same side easy, anyways port area need to be like 35 square inches per driver for those L4s likely more at high tuning, anything above 37Hz tuning will not be that nice on rap music and such.

It's an '01 which has a much more narrow section in the center of the trunk than the '04+ & has made it difficult to get a 28" rubbermaid container in & out. So I don't think the box can be that big, especially with 66 pounds of woofers + box weight. If it was smaller & fit in my hands like a dumbbell or something, I could lift it comfortably by myself without damaging it or blowing my back out, if I need to get at the spare tire. That's why I am considering just using the back seat instead. If I can get it in there once, it won't ever have to move & there's more flexible dimensions to the box if need be.

What size or how many ports would you recommend for a 3 cubic foot box @ 37hz? I was hoping to use a prefab 4" aeroport like they sell on sonic electronix, but if you think multiple 3" or 4" would do the job better, I'm open to suggestions. I figured 3" would have a lot of port noise even if I split the box with a baffle so they were 1.5 each (after displacement), & the calculator at 12volt only really calculates tuning for 1 port, so I'm rather clueless when it comes to multiple ports. I was also thinking about using the top, back, or front for the ports (trying to keep them all on one side), and not on the same side as the subwoofers, if that helps at all.

This is my first build over 1200 watts and I haven't built anything since 2011, so I feel really out of the loop at the moment & I really appreciate your replies. Thanks again.

[Triticum Agricolam]

So if you are planning on upgrading to a 3000 watt amp down the road, you should determine your port size now based on that or you may have to rebuild the box when you get the new amp.

I completely agree with Joe X's recommendation of 35 sq in of port area per sub. So that's 70 sq in total. A single 4" aero port is just over 12.5 sq in. You can get away with a little less port area with aero ports (like 20% less at best), so if you want to stick with them two 6" ports should work well. They are each going to have to be nearly 33" long though to get your tuning where you want (37 Hz). That may be hard to fit in your box. A 70 sq in slot port may be a more reasonable solution.

If you want a port calculator that can handle multiple ports, this one works well:

http://www.carstereo.com/help/Articles.cfm?id=31

[InfiniteRuckus]

Yeah, that is the plan, to build it to full potential & just run with less power (for now). Thanks, you've given me a lot to think about and plenty of numbers to crunch. Luckily, I have another month or two to do it.

[Triticum Agricolam]

No prob! Let us know if you have any other questions.

[InfiniteRuckus]

Since the ports have to be so long anyway, I might as well go back to a traditional style by facing the subs to one side, but now I'm going to put the ports on the sides (one on each side, one above the other). My question is, how far away from the wall is a safe distance for the inside port flare without causing turbulence or restricting their movement? Originally I thought I was going to be dealing with a 4-5" port so I wasn't concerned, but now that will determine the overall minimum length this one can be. Thanks again.

[Triticum Agricolam]

Ideally, ports should be one port diameter away from any walls or other obstructions. You can get away with a half diameter without it affecting airflow, but it will probably lower the tuning some.

[toenuts]

I building a subwoofer enclosure with 4 American bass tnt 1244 and have 4 6inch aero ports. is it possible to put subs on one wall facing and ports on opposite side