I am building my own band pass box for the XB, the dimensions are going to be 15 inch deep by 30 wide by 17 high. I have been doing a lot of research on band pass boxes and it seems the most common type for two subs would be a three chamber single reflex where the two subs face each other with a port splitting them in the middle. I have a friend where I used to live who has this type of box but I believe his was a down firing box which would place the subs face down firing in one chamber towards a large port at the bottom of the box but this takes out the three chamber effect and causes it to become a two chamber. I have two audiobahn 12's that are going to be going into this box and they will fit into either box. Which box would hit harder and be worth my time???

 

I'm not sure I'm understanding that second box. You say down-firing facing a port, but then you mention only a two-chamber, yet still having 2 12s. Do you mean the drivers are loaded isobaricly, from a sealed to vented chamber? This would be an Iso Single-Reflex Bandpass enclosure and would be less efficient than a standard Single Reflex BP with two 12s. It would, however, cut the size of the enclosure approximately in half.

 

i just finished building a box my self for my xb - my orginal plan was to build a bandpass with 2 10's - then i started thinking by the time im done building this thing its gona weight a ton - so just for the hell of it i wanted to see what 1 10'' sub can do in a sealed box - so i got to it about 2 hours later i was done - now for the moment of truth , it was amazing the bass is so much richer and deeper il never use a ported or bandpass box ever again

so this is my setup SONY 2200gtx amp , 1 10'' rockford fosgate punch he sub (its old back from 01 i think) , a sealed super lite and super compact box custom made by me its 12x12x10 its 0.7 cubic feet

 

Sealed enclosure=more accurate response, yes, but not necessarily a deeper tone (lower frequency). Vented enclosures, when properly built for their specific woofer and objective, can hit VERY low frequencies. The same can be said for bandpass enclosures. My point is, a properly built enclosure is going to meet its set objectives. Sealed, Vented, BP... all can be tailored to perform well below human hearing.
The different enclosures vary more on Enclosure Size, Accuracy, and SPL than they do anything else. Yes, there are other variables, but these are the main 3 that vary dramatically from the different enclosure types.
Certain woofers are designed to perform better in certain types of enclosures. Just because one woofer performs better in a sealed box does not mean that all woofers will perform at the same expectations in the same type of enclosure.

 

I used paint and did a quick sketch up of it, obviously not drawn to scale and not drawn in 3D but figured this would get the picture across.
[img]https://s17.photobucket.com/albums/b78/socalaxplyr/Car/?action=view&current=sub.jpg&refPage=&imgAnch=imgAnch1

 

OK, I understand now. They are still both considered a single reflex bandpass. It would be better to have each driver in its own chamber, but the function is still the same. My vote is for the 3-chamber single reflex simply for the CYA effect if one of the woofs were to blow. One blown woofer is always better than two.

 

What about putting a wall inbetween the two woofers that are downfiring? I just want to make sure the box I make works like the one my friend has because his hits HARD and he has two no name 10's but at the same time the CYA aspect comes into play WHATS YOUR OPINION

 

I would separate the 12s, having each perform in their own sealed chamber. Building a wall between the two would accomplish this. The important part is to ensure that the enclosure is designed to optimize the output of the specific woofers in use. As I am sure you know, a bandpass enclosure acts as a "filter" by design. It does exactly what its name implies; allow a specific frequency band to pass much like a crossover on an amplifier, only nowhere near as accurate. If the enclosure is not designed to best suit the woofers used, it could produce very poor results and a very narrow frequency range. The angle of the woofers relative to the vent inside the bandpass enclosure does not play a significant role in the output of the setup so long as the woofers are not making direct contact with the vent, itself. The direction the vent faces is still going to be the loudest point, much like a regular vented enclosure.
Even though a well-designed bandpass enclosure will act as a crossover, there is the problem with transient frequencies produced by the enclosure structure or even the vent, itself. Some sort of crossover is still necessary to eliminate these frequencies.
Be very careful when making your final adjustments on your amp gain. A bandpass enclosure, especially at high volumes, can be very difficult to distinguish where accurate bass ends and distortion begins. Overdriving the woofs too hard can drastically shorten their lives.

 

I some poted emclosures are amazing...I have used many in pro-audio and you would be surprised look at the sound sytem in my profile....that is only the front stage LOL