So I was thinking...........6th order, now to understand it. QUESTIONS!!!

[rocking.that.eclipse]

john hones rig was like that before he tore it out to bag it

look his dually up... twas a bit windy

[scooter99]

Hey guys, I was doing some looking at 6th orders and trying to understand them a little bit. I've come across a few things, even a thread on here, and I'm not sure if I'm understanding them correctly. Maybe some of you can shed some light.

So What I was thinking was similar to what I drew out for my idea of a "ported enclosure". I thought about a different idea now.

What I've been reading is about ratio's and tuning. This would probably end up being a series 6th order, which is when the rear port goes into the front chamber and then that front chamber has a port also. Like so: top one - quasi-sixth order series tuned bandpass

Reading this site: http://www.diysubwoofers.org/bnd/6thord4.htm I think I'm becoming more confused. It says " A standard 6th Order bandpass design calls for the following alignment parameters:

Vf = 0.75 cu.ft., Ff = 80Hz
Vr = 2.25 cu.ft., Ff = 30Hz

First of all, Vf is the Volume Front correct? Which if correct, would make Vr Volume Rear right? Then Ff is frequency tuning right?

Second question, if you look throughout the page in that link, it never says the size of the subwoofer being used. So how do they determine that a .75 front and 2.25 rear are used? Isn't the air space determined by the size of the sub and the specs on it as far as desired air space for sealed and ported enclosures?

Ok let's move on to the vent. If I'm reading this correctly, the ports need to co-mingle, if you will, to get the desired tuning. They suggest the front and rear vent sizes should match. For instance if the front vent was 9 x 10 then the rear vent should be 9 x 10. Is this accurate or does it really matter as long as the tuning is where it needs to be. So a 9 x 10 vent is 90 sq in of port area. As long as I still had 90 sq in of port area for the rear then it should still be good right?

In this case they're saying they're using a 4" aero port. To tune the front (.75^ft) to 100hz would take a length of 4.11". Then to tune the rear (2.25^ft) to 30hz would take a length of 13.76". Then they subtract the front vent from the rear vent for some reason, which I don't know why. They get 9.65" of length (13.76 - 4.11 = 9.76). So my assumption is that they were doing the 100hz to get a total number combined. They subtracted the value of the front port (4.11) from the rear port (13.76) which gave them the rear vent length, or inner vent length. But if that's the case then they're still not at an 80hz tuning right? Simple math would say that 100 - 30 is 70. So this is a bit confusing to me.

So how does all this work out? What should the air spaces be. Say I had a sub (15") and the ported recommendation was at 3.5 cu.ft. per sub. The rear chamber, in this case the bottom chamber, would then be 3.5 cubes, and then the front chamber would be the same in a 1:1 ratio correct? Is an 80hz front and 30hz rear tuning a good way to go after tuning or should it be lower front tuning, say around 60hz?

Thanks for any help guys.

Here's a quick little drawing of what Im thinking.

After looking at that one I did a little tweak. Something tells me that 90 degree corner up top would be an issue.

[scooter99]

Ok I just came across this article, which makes some sense while just doing a quick skim read (I'm at work hard to get into depth on anything right now). I'll read it a bit more in depth later when I can dissect it and try to understand it better.

But from this, and the quick read, it basically is saying that the 6th order acts as band pass tuning crossover. That if you want the higher tuning at a certain level, then that's what you tune the front chamber to. The lower desired tuning would be the inner chamber or rear chamber port. Or maybe that's backwards. Anyway, I'll have to re-read it and clarify it.

It also, just their experience and what they've used, suggest a 3:1 ratio.

Very interesting to me.

[Triticum Agricolam]

I'm on my phone right now so I can expand on some of this more later.

Two things to keep in mind:

1. With series tuned boxes both ports interact with each other. As you change the tuning of one, it will change the tuning of the other. This can make getting the tuning you want VERY difficult. Only a couple different modeling software acurately shows this. Hornresp does and I believe BassBox Pro does too.

2. Delete from your brain anything you have heard about "ratios". Seriously it's the completely wrong way to look at chamber sizes. You need to size them independently not as a "ratio" to each other.

[scooter99]

I actually just read through your experiment thread. I'm highly impressed. I will download Hornresp when I get home on my home computer and go to work to understand it.

Most of what I've seen out there, front and rear chamber combined, actually come out really close to the recommended ported specs of the subs. Do you find this accurate at all? Not talking about ratios, but just overall size. DOes that make sense?

I was hoping you'd comment on this btw. Thank you.

[Keith77]

See some one that knows what the hell they are talking about chimed in LOL

[scooter99]

LOL, yes he did. I can't wait to get home and play with that software.

[Triticum Agricolam]

...Most of what I've seen out there, front and rear chamber combined, actually come out really close to the recommended ported specs of the subs. Do you find this accurate at all? Not talking about ratios, but just overall size. DOes that make sense?...

Generally speaking I've found 6th order bandpass boxes are going to require more space than what a ported box would, but its very situationally dependant.

If you need any help with Hornresp just let me know, it's not the most intuitive software to use, but it's VERY powerful.

[scooter99]

Ok sounds good. I have the whole bed of my truck to play with, although if I can avoid using it all, that would be ideal.

Thanks for the information, I appreciate it.