The 4th order thread

[RangerDangerV2 5,000+ posts]

gah, toasted my 3500. blew a few output fets. oh well, at least I can fix it myself. just got to wait on my fets and drivers to get here, and I might mod it to do 5k@1. but well see if I feel like pulling the board or not

 

[jdawg90 10+ year member]

I take it Vb is box volume? Is that sealed or ported? I plugged that number in the formula you gave for Fc with the specs and reccomended ported box specs for the sa-12 v1 and v2 and got around 100 both times. For the sealed box volume I got closer to 200.

The formula is Fc=sqrt[(Vas/Vb)+1]*Fs correct?

 

[RangerDangerV2 5,000+ posts]

I take it Vb is box volume? Is that sealed or ported? I plugged that number in the formula you gave for Fc with the specs and reccomended ported box specs for the sa-12 v1 and v2 and got around 100 both times. For the sealed box volume I got closer to 200.
The formula is Fc=sqrt[(Vas/Vb)+1]*Fs correct?

100 or 200 what? sa12 for example. vas=21.21, fs is 33.7. now, take 21.21/28.3168(1 cu ft in ltrs) this will give you .75 if you round it. now, add 1, and you get 1.75. then sqrt that and you get 1.33, then multiply that by the fs, so 33.7*1.33 and you get 44.821. that is your Fc.

 

[shauncox26]

Hey guys newb on the 4 ths. Going to try on with my obsidian 12 s. So the larger chamber should be the ported one.

 

[RangerDangerV2 5,000+ posts]

Hey guys newb on the 4 ths. Going to try on with my obsidian 12 s. So the larger chamber should be the ported one.

yes.... did you read the first page? I would start there

 

[shauncox26]

Yes i did. Ok oas fs is 33 and the vas is 34.4 vb is 1.5 ft2 or 42.4752 lts. I came up with 44.3982 for my fc. So i tune my ported chamber to around 44 hz correct. So much to take in.

 

[RangerDangerV2 5,000+ posts]

Yes i did. Ok oas fs is 33 and the vas is 34.4 vb is 1.5 ft2 or 42.4752 lts. I came up with 44.3982 for my fc. So i tune my ported chamber to around 44 hz correct. So much to take in.

yup, youre on the right track

 

[shauncox26]

So i was thinking 1:3 was a good starting point. Ill post pics once i start.

 

[Buck 5,000+ posts]

I may try 1:2 first.

 

[jdawg90 10+ year member]

100 or 200 what? sa12 for example. vas=21.21, fs is 33.7. now, take 21.21/28.3168(1 cu ft in ltrs) this will give you .75 if you round it. now, add 1, and you get 1.75. then sqrt that and you get 1.33, then multiply that by the fs, so 33.7*1.33 and you get 44.821. that is your Fc.

I didn't pay attention to units... I'm getting the right answer now.

What's the difference in using a passband ripple (S) of .5, .6, and .7 when designing a box?

 

[Beatin' 10+ year member]

what!? The ported chamber has to be the bigger one? WinISD shows too much peak and group delay.

 

[RangerDangerV2 5,000+ posts]

I may try 1:2 first.

I would disagree, its easier to shrink down than gain more space.

what!? The ported chamber has to be the bigger one? WinISD shows too much peak and group delay.

forget winisd, it is highly innacurate.

 

[RangerDangerV2 5,000+ posts]

I have been getting quite a few pms lately, and it seems that all of you think that you need winisd to design a 4th order.... well, you dont. take the steps that have been explained, build it, test it, enjoy it.

 

[RangerDangerV2 5,000+ posts]

people.... if you pm me asking for advice, then listen to what I have to say. dont keep asking me about modeling programs, because they are useless. Ive had to tell about 10 people that in the past 2 days, and nobody is listening. If you pm me, and dont listen to my advice, then I will not respond back.

 

[jdawg90 10+ year member]

How does a high ratio effect the frequency spectrum the sub plays at ? Does it simply shrink it with the peak being the higher? In your pm you said if you want to hit the lows go with a larger FC. What exactly do you mean by that? A sub with a higher FC (I'd think it'd be the opposite, that's why I'm kinda confused)?