# Subwoofer box design help



## XtremeRevolution (Jan 19, 2012)

How much space can you afford to give up and what kind of sound are you going for?

Don't plan on an adjustable port. Design it with a static port size from the get go based on the kind of output you want or run two ports of two different sizes based on your needs. You'll need a shared airspace to pull this off.

Those subs will require at least a double thick baffle if not a flush mount with a 1" mounting plane.

Are you getting the box in through the trunk or the back seats? If back seats, are you removing the seat backs first? That will make a big difference in how bit of a box you can use.


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## trevor_geiger (Nov 29, 2012)

I'll remove the back seats if necessary(I just put them back in a few weeks ago after having them out for about 5 months lol). And of course you know the max width and height already, it's just the matter of depth I can give up. I'm not sure if I want to seal them off and fire them into the cabin or close up the seats and fire them into the trunk lid. When I was reading up on aeroports they say a slot ported box needs 12-16 inches of port per cubic foot of box when aeroport would need 6-8 inches. Andrei if it is easier to text or call about this I have your number still just let me know.


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## trevor_geiger (Nov 29, 2012)

I've used 3/4" Mdf on the past two boxes and this time I'm going to go with 3/4" birch double baffle and quite possible flush mount the subs and aeroport. And as for sound, I still would like it to be musical (play notes 28-50) the last box I had I tuned real low and I would lose anything above 44 so this time I don't want a low end monster I want something that'll sound great on all the notes.


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## hificruzer226 (Mar 27, 2013)

what is your desired f3? what S factor do you want (.7,.6,.5)? isobaric loading?


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## trevor_geiger (Nov 29, 2012)

hificruzer226 said:


> what is your desired f3? what S factor do you want (.7,.6,.5)? isobaric loading?


I don't know what you mean by those lol are you talking about a 4th order?


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## XtremeRevolution (Jan 19, 2012)

I don't see this working with a bandpass box. No way. As for port, you need to model them to see what your vent velocity looks like, not just go with some arbitrary number someone put out there for port surface area. 

Birch is nice but not as dead as MDF. You'll need some very thorough bracing. 

Texting would be easier.


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## hificruzer226 (Mar 27, 2013)

Bandpass enclosures are very hard to make correctly with musicality/accuracy in mind especially with subs that aren't designed that way from the start. If you want to be able to have play as accurately as possible and you havent built a ton of enclosures before I am going to recommend sealed 1.25 cft per enclosure easy and cant go wrong. If your intentions are maximum SPL then a folded horn is what I would go with.


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## XtremeRevolution (Jan 19, 2012)

hificruzer226 said:


> Bandpass enclosures are very hard to make correctly with musicality/accuracy in mind especially with subs that aren't designed that way from the start. If you want to be able to have play as accurately as possible and you havent built a ton of enclosures before I am going to recommend sealed 1.25 cft per enclosure easy and cant go wrong. If your intentions are maximum SPL then a folded horn is what I would go with.


Not sure if two enormous motor 12" SPL subs would play at their potential in a sealed box or if a folded horn with two would even fit in a Cruze.


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## hificruzer226 (Mar 27, 2013)

trevor_geiger said:


> I don't know what you mean by those lol are you talking about a 4th order?


Yes single reflex ie 4th order, I am asking several things so I could calculate your dimension and see how close we can get you to your desired freq.


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## trevor_geiger (Nov 29, 2012)

So I take it's a no go on a 4th order? That leaves me with an aeroport.


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## hificruzer226 (Mar 27, 2013)

trevor_geiger said:


> So I take it's a no go on a 4th order? That leaves me with an aeroport.


Not unless you can figure out how to get 15+ cubic feet of box in the car


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## hificruzer226 (Mar 27, 2013)

unless you run isobaric


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## trevor_geiger (Nov 29, 2012)

That's what I would do if I wanted to run a 4th but I'm going to aeroport.


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## trevor_geiger (Nov 29, 2012)

XtremeRevolution said:


> I don't see this working with a bandpass box. No way. As for port, you need to model them to see what your vent velocity looks like, not just go with some arbitrary number someone put out there for port surface area.
> 
> Birch is nice but not as dead as MDF. You'll need some very thorough bracing.
> 
> Texting would be easier.


Just sent you a text sir.


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## hificruzer226 (Mar 27, 2013)

To me an aeroport is just a flared rounded vent. Are you talking about a bass reflex or ported enclosure?


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## trevor_geiger (Nov 29, 2012)

hificruzer226 said:


> To me an aeroport is just a flared rounded vent. Are you talking about a bass reflex or ported enclosure?


Just a box with a hole in it. And a tube with flared ends for the port


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## XtremeRevolution (Jan 19, 2012)

I just call them flared ports. Aero ports sound too...DIYMA.com. Those of you who have spent some time, and graduated from there will know what I mean. You can get them in 2", 3", 4" and 6" diameters, either smooth or dimpled. A single 15" sub will generally run off of two 4" ports. Two 12s...I'd have to see what the vent velocity would be. Problem is that the bigger you make them, the longer you need to make them to maintain the same tuning, and you can't bend them like you can a slot port. Best bet will be to fit the box in through the rear so you can get the ports as big as you can, and run the box 17" tall, 32" wide, side fire the ports, and as deep as you can afford to make them. Then, you could probably run two 6" ports or three 4" ports and not have any issues with vent velocity. Again, I'd have to model the enclosure to determine what sizes would be appropriate for your tuning frequency.


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## trevor_geiger (Nov 29, 2012)

So what you are saying is subs firing forward into the cabin or back towards the trunk lid and have the ports on the sides?


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## XtremeRevolution (Jan 19, 2012)

trevor_geiger said:


> So what you are saying is subs firing forward into the cabin or back towards the trunk lid and have the ports on the sides?


Yep. I don't really see any other way that you could get the ports long enough for the size you need.


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## trevor_geiger (Nov 29, 2012)

XtremeRevolution said:


> Yep. I don't really see any other way that you could get the ports long enough for the size you need.


Hmm well would it really be efficient to have it that way or go ported and seal it off if I want to fire into the cabin or fire them towards the trunk lid.


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## XtremeRevolution (Jan 19, 2012)

trevor_geiger said:


> Hmm well would it really be efficient to have it that way or go ported and seal it off if I want to fire into the cabin or fire them towards the trunk lid.


If you seal it off, the subs and the port have to fire into the cabin. The trouble with this is that you are now restricted in box volume by the size of the trunk opening as you have to work from inside the trunk. If it was me, I'd keep it simple and just run the subs rear firing with a side firing port.


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## trevor_geiger (Nov 29, 2012)

XtremeRevolution said:


> If you seal it off, the subs and the port have to fire into the cabin. The trouble with this is that you are now restricted in box volume by the size of the trunk opening as you have to work from inside the trunk. If it was me, I'd keep it simple and just run the subs rear firing with a side firing port.


Hey man whatever is simple, and sounds good. I don't have any problems with removing the back seats if needed but then again I wouldn't mind just sliding it through the trunk opening.


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## XtremeRevolution (Jan 19, 2012)

Subwoofer displacement: 0.36 cubic feet
Port displacement: 0.82 cubic feet
Net internal volume: 4.75 cubic feet
Total gross volume: Approximately 6 cubic feet

Ports: Four Precision Sound Products 4" Flared port at 25" length. Requires extensions and couplers. Mathematical tuning at 32hz. F3 at 33.19hz with high pass filter (see below). 

Side fire the ports toward the rear, all on one side. 

17" Height
33.5" Width (includes recessed lip)
25" depth (includes triple thick baffle with flush mount)

Subs will clear inner flare by at least 2.9 inches and port tube by 3.9 inches. 

Recommended high pass (subsonic/infrasonic) filter set to 25hz at 24db/octave. 

Vent velocity reaches 37 m/s with 8,000W peaks and heavy fiberglass fill. At 8,000W peaks, subwoofers remain within 10% of rated xmax. 

Better have a lot of power to feed them...


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## trevor_geiger (Nov 29, 2012)

Can't wait sir!


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## hificruzer226 (Mar 27, 2013)

XtremeRevolution said:


> and you can't bend them like you can a slot port.


Why cant he bend them?


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## XtremeRevolution (Jan 19, 2012)

hificruzer226 said:


> Why cant he bend them?


Short of getting a PVC fitting, thin PVC pipe doesn't bend.


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## hificruzer226 (Mar 27, 2013)

XtremeRevolution said:


> Short of getting a PVC fitting, thin PVC pipe doesn't bend.


I understand you cant bend pvc. I thought there was a sonic reason you didnt want him to run 90deg fittings other than a little turbulence.


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## XtremeRevolution (Jan 19, 2012)

hificruzer226 said:


> I understand you cant bend pvc. I thought there was a sonic reason you didnt want him to run 90deg fittings other than a little turbulence.


Naturally, you want as few bends as possible and preferably none, but with enough port surface area, it doesn't make all that much of a difference.


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