I'm going to be starting a 4th order blow through my rear deck soon and had a few questions. One being when I port through my rear deck would it be best to fallow to window angle to port straight up into it?

Bandpass or conventional 4th order vented?

There's a difference? Sorry I only know it by a 4th order bandpass. The enclosure that's a sealed box on one side and a ported on the other.

There is a difference. 4th order has nothing to do with being a bandpass. It has to do with the enclosure roll-off.

I haven't built a blow through before, but if you design the enclosure right, it shouldn't make a huge difference in output regarding how you route the vent into the cab. One thing to remember, the less turns the air has to make to get through the vent the better....

I have however built about 20-30 4th order bandpass boxes, so I know a thing or two about them...

So what's the 4th order bandpass that I hear everyone talk about on like ****? The ones that play loud low and move a lot of air. Its a sealed rear chamber and ported front chamber. That's a 4th order right?

Yes that is a 4th order bandpass. This means the box will give you a 24db slope of drop off per octave at the low and high ends of the frequency response. And a qtc of .7

9 times out of ten the people building these boxes aren't building 4th order bandpass boxes. They are simply building a closed(sealed) bandpass box since the response of the box doesn't represent a 4th order butterworth filter.

So, if you are Truely wanting a 4th order enclosure it would be just as easy to build a ported enclosure and get the same response unless you are limited by area such as a blow thru

OK, thank you. So basically now I'm lost lol. Right now I have 2 12in DC level 3m2s on a DB Drive A7 2500 in a 4 cube box tuned to 34hz with 15sq in of port per cube. The rear seat of my 2000 Audi A8 is as solid and sealed up as fort Knox. I cut out a hole roughly 18x30 in my rear deck and hat shelf the glassed it to make it clean again to release to pressure from the trunk.

My theory is if I build a 4th order and seal it to the rear and blow through what was once a rear deck it'll yield higher numbers while having a wider range, move a lot more air and no loss of out put into the trunk. Am I correct on my thinking or am I off?

Yes your correct. You were just mislead on the name of the enclosure. You just need to model the enclosure to your desired output response.

Although the wider range is incorrect. The same range can be obtained from a ported enclosure

OK wider range then I have now lol, my current lpf has to be set at 45 an ssf is at 33 lol. I would like to play between high 20s to mid 50s. I don't need to play as low as some people with 4ths, I don't listen to chopped and screwed, but occasionally my music drops below 30.

So what's the 4th order bandpass that I hear everyone talk about on like ****? The ones that play loud low and move a lot of air. Its a sealed rear chamber and ported front chamber.

You are reading posts from a bunch of confused people. It is absolutely not a good design for most of those installs. In that application as the compromise is ridiculous. Those boxes have their places and in your particular application CAN be a good idea but the box design and implementation must be done correctly. Direct firing into cabin from trunk is reason I'd support to run that alignment, but for "moving air" and playing loud and low there are other more logical ways to reach those goals.

What other ways, I've tried so many things but a 4th that's all I can think of now. 2 12s is the most I can fit in my trunk and I can only do 142.8 on music, I want to be louder, possibly move some hair and and have a wider range while doing all this.

Without knowing anything about your equipment, your available space, etc etc it's impossible for us to assist.

2 12 DC level 3m2, DB Drive A7 2500, I have about 7 cubes available total. Soon will be another A7 2500 and 2 12in DC XLm2s

Huh, you are going to run 4 subs of which there are 2 different sets?

What do you currently have for a box and what doesn't it do that you want?

Watching this have same sorta interest

Amazing how people can't google the difference between a 4th order vented and a 4th order BP.

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