1. ## Re: The 4th order thread

Originally Posted by Nut Hair Trick
A true 2:1 ratio of my available space of 127.99 would be 42.66l (1.5 cuft) and gives me an FC of 42.32
If I used 2cuft for the 2 sa12s or 56.63l for the sealed chamber, I get an Fc of 40.22.

The smaller Sealed chamber gave me a higher Fc. I tried it again with both volumes using the T/s parameters on SSA's site and I got much lower FC's 39.6 (42.66l or 1.5 cuft) and 37.155 (56.63l or 2 cuft). I can not access the sundown site because it asks me for a password. The only T/s parameters I can trust right now is that of what Pete extracted. I know this may sound dumb, but would the T/s parameters that I have access to change due to me using (2) D4 Sa12's?
youre doing something wrong here, you cant use the whole volume of the rear chamber in the equation, because you have two woofers, so you need to use 1/2 of it. makes sense? so, with my tsp's for my sa12, which yours should be close, if you use a 1 cu ft rear chamber per woofer, that will give you an Fc of 44.57hz. Now, since it seems that you want to do a 2:1 ratio, you will need a rear chamber of 2 cu ft, and a front chamber of 4 cu ft, from what I can understand, you have 4.5 cu ft of GROSS volume. so in essence, you dont have room for a 2:1.

2. ## Re: The 4th order thread

Originally Posted by RangerDangerV2
youre doing something wrong here, you cant use the whole volume of the rear chamber in the equation, because you have two woofers, so you need to use 1/2 of it. makes sense? so, with my tsp's for my sa12, which yours should be close, if you use a 1 cu ft rear chamber per woofer, that will give you an Fc of 44.57hz. Now, since it seems that you want to do a 2:1 ratio, you will need a rear chamber of 2 cu ft, and a front chamber of 4 cu ft, from what I can understand, you have 4.5 cu ft of GROSS volume. so in essence, you dont have room for a 2:1.
Understood, thanks

3. ## Re: The 4th order thread

Now I have an Fc of 46.3 using 1cuft in volume for each sub for a total of 2 cubes sealed. that will leave me with 2.5 for vent area but that doesnt account for the baffle for each sub as well as .14 displacement for each sub. This is going to be a trunk build with the 2 sealed chambers facing each other with the vented chamber being in the middle porting through the arm rest. The 2 compartment areas (sealed and ported) just might be **** close to being even, unless I were to reduce the size of the sealed compartments.

4. ## Re: The 4th order thread

Originally Posted by Nut Hair Trick
Now I have an Fc of 46.3 using 1cuft in volume for each sub for a total of 2 cubes sealed. that will leave me with 2.5 for vent area but that doesnt account for the baffle for each sub as well as .14 displacement for each sub. This is going to be a trunk build with the 2 sealed chambers facing each other with the vented chamber being in the middle porting through the arm rest. The 2 compartment areas (sealed and ported) just might be **** close to being even, unless I were to reduce the size of the sealed compartments.
a word of advice, more ratio>cone area. so if you have to drop it down to 2 10s, or 2 8s to allow a larger ratio, then do it. this is talking spl wise of course though.

5. ## Re: The 4th order thread

Originally Posted by RangerDangerV2
a word of advice, more ratio>cone area. so if you have to drop it down to 2 10s, or 2 8s to allow a larger ratio, then do it. this is talking spl wise of course though.
Sounds good, and I do see what you are saying in order to have an efficient 4th order band pass. But, i dont even have to go with a 4th order just for the sake of doing so. I do know with my space available, I have enough room for say (4) 8's, (3)10's, (2) 12's, or (1) 15 for a basic ported enclosure.
My goals are certainly more musically oriented with a flat response from mid 20's to low 60's or even high 50's,with a little SPL. I have mids that can drop to the low 50's so I say high 60's for overlap. It is nice to run the numbers to see what a 4th order can do and learn about them. I could just as easily construct a ported box, waveguide, or tapered t-line to achieve my goals. Thanks for your help.

6. ## Re: The 4th order thread

Originally Posted by RangerDangerV2
tested more today... couldnt get more than the 145.18, morning it averages 144.5ish, midday and night after its been in the sun all day it meters about a 141.5. really amazing how much the temp of the vehicle matters. but ive got some plans, so hopefully Ill see that 150 by sunday.
So did you find that 150?

7. ## Re: The 4th order thread

Originally Posted by hispls
So did you find that 150?
nope. was doing 47s, on 1k. but now im out of car audio. more time testing and I could have.

8. ## Re: The 4th order thread

I suppose it is possible to do an IB setup and add a front chamber so you can have a huge rear "chamber/trunk" that allows the sub to dig down low. What are the cons to this type of 4th order bandpass?

9. ## Re: The 4th order thread

Originally Posted by Beatin'
I suppose it is possible to do an IB setup and add a front chamber so you can have a huge rear "chamber/trunk" that allows the sub to dig down low. What are the cons to this type of 4th order bandpass?
Double post

10. ## Re: The 4th order thread

IB does not equal 4th order bandpass

That's called a ported box

11. ## Re: The 4th order thread

Originally Posted by Tenacious.
IB does not equal 4th order bandpass

That's called a ported box
the trunk would be sealed off from the front chamber and cabin. Therefore, giving the rear of the subs the same cubic feet of volume as the trunk would have. The front chamber that is firing into the cabin and sealed off from the trunk would be tuned low to give you horrific low end extension at the cost of upper end bass.

That would be a 4th order bandpass that uses the trunk as the rear chamber. My question is, what are the side effects of having a rear chamber that big?

12. ## Re: The 4th order thread

Originally Posted by Beatin'
the trunk would be sealed off from the front chamber and cabin. Therefore, giving the rear of the subs the same cubic feet of volume as the trunk would have. The front chamber that is firing into the cabin and sealed off from the trunk would be tuned low to give you horrific low end extension at the cost of upper end bass.

That would be a 4th order bandpass that uses the trunk as the rear chamber. My question is, what are the side effects of having a rear chamber that big?
You're not understanding here... You literally just described a ported box with the port firing forward and subs firing into the trunk.

13. ## Re: The 4th order thread

Here's me new box:

14. ## Re: The 4th order thread

4th order peeps opinions....i've got a 10" 2004 XXX layin around (I can recone to whatever if i wish) and a 12" Eclipse TI collecting dust. As far as a daily driver, without giving a **** about numbers, just lows and loud (while retaining sq) what are my best options for a 4th order build??. Power isn't an issue, but want to limit this to a 10 or 12 (again, either can be reconed if necessary)

15. ## Re: The 4th order thread

can you put polyfill in the ported chamber of a bandpass to make it appear bigger to the woofer?

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