Some have heard me talk about this so here it is. Also, I want it to be here so I don't have to go searching for it every time someone asks about it.
A little bit about the box. The dims are: 35 1/2"W x 21"D x 14"T, it was built with 3/4" MDF and sealed up with wood glue and liquid nails. Also about 100+ screws!!
It's an ABC box so it has two chambers. Here is a quote from the man himself(HexiBase) about it: "The cumulative internal volume of the loaded chamber is 2.621 CuFt, and 1.132 CuFt for the empty chamber. There are two tuning points, one around 25Hz and another around 36Hz. Factoring in for the vent resonance, your F3 should be somewhere between 19Hz - 20Hz."
Who knows, I still have it, but it's just sitting in my basement. I don't even have the sub any more, but I'm sure something else would do just fine in it.
That is really just a ported box. The second chamber does nothing. It will only add to the length of the middle and far ports, creating a single port length.
Then the two ports will likely add together in some way to a single tuning. When you put two ports of different length in a box, the higher tuning tends to dominate, as the woofer will unload below this frequency, at which point a longer port tuned lower is just chuffing air.
You could actually run an impedance curve on this box with a DMM and a test tone CD to verify the tuning of it.
Aside from this though, good job on the box. The construction looks solid and well thought out.
Very nice job on the box. You should either carpet or vinyl that thing and it will look even better. Vinyl might not be the best idea unless you have your screw holes countersunk and put wood filler over them.
Head Unit: Eclipse CD5000
Amp1: Ti 500.4
Amp2: MPS2500
Crossover: Audiocontrol 6xs
High/Mids: ID CD1-E v1 Horns
Midbass: IDQ 6.5 v2
Subs: IDQ 12 v1
EQ: PG EQ215-X
Eric D wrote:That is really just a ported box. The second chamber does nothing. It will only add to the length of the middle and far ports, creating a single port length.
Then the two ports will likely add together in some way to a single tuning. When you put two ports of different length in a box, the higher tuning tends to dominate, as the woofer will unload below this frequency, at which point a longer port tuned lower is just chuffing air.
You could actually run an impedance curve on this box with a DMM and a test tone CD to verify the tuning of it.
Aside from this though, good job on the box. The construction looks solid and well thought out.
Actually Doc it's a little more than that. Read, learn, here.
It is pretty hard for me to argue against the link you have posted, but I will do my best…
Those calculations, and that box design is all done at what is known as “small signal”.
This is typically what you deal with when you read about 1W, 1V, or 1 meter parameters. The purpose of using 1W, 1V, or 1 meter is such that variables drop out in elaborate calculations.
The real world is closer to what is known as “large signal”, and to my knowledge, only recently have TS parameters and box equations started revolving around large signal measurements and calculations.
At large signals, things tend to break down, or misbehave. It is not even entirely possible to simulate large signal behavior, trial and error seems to be the best path to success. These are the principals which the insane SPL vehicles are based upon. Try as you may, you cannot calculate the ideal box for an SPL vehicle, as all of the math breaks down when other non linearities are introduced.
I do not expect you to believe what I am posting, as I am no expert. All I suggest is you consider what I have posted and run your own tests.
I have built a box like yours before in the laboratory, and it did not work as predicted when using it at listening levels of power. At 1W measurements it was close to calculated, but beyond this, it was just a box with a single port in it, despite all the other complexities to it.
Well, because I'm not an expert either I kinda get what your saying. Real world vs tests on paper, I get that. I did fail to mention that this perticular box was designed for a specific sub and my specific vehicle. The designer (HexiBase of Team Toxic Bass) did do some sonic measurements of a vehicle of the same make and model year of mine, and designed the box around these measurements. The results were stunning to me. Because of the dual tuning of the box it had great sound quality, but had a great range of frequency's it could play. I really, really wish I had the room to do another box like this, it was by far the best sub stage I have heard in any of my vehicles. The only downside is the size of the damn thing.
If you can get your hands on it, I would really like to see an impedance curve of the box in your vehicle.
Even better would be both small signal (1W) and large signal (say 10W) curves to show the differences.
Additionally, keep in mind all of the tuning and all of the effort into the design change when you roll the windows down, or if an additional passenger sits in the vehicle.
If this box works for you, and sounds great, then there is not much more to say. But, I am highly confident you could get the same sound with a box half of the size. If you happen to be after more cargo space, this may be a benefit for you. If not, then it would be a waste of time.
Actually, I don't even have that vehicle any more. This was a build I did a few years ago. I still have the box, but only because I have no idea what to do with it. In the future I might try it in a home theater system just to see what it will do.
As far as the design I really don't know much since it was designed for me. I might have the design for this particular box somewhere if you want. But that's about the best I can do for you. I hear these designs are a little bit quirky, by that I mean if it's not designed properly it sounds like poopoo.
In the future I might try it in a home theater system just to see what it will do. 
