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Starting my box on wednesday, 4th order blowthrough.


DirtyDuzit

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So i've been preparing for a blowthrough for a bit now I got 2 Ct stounds tropo 18's and a skar 2k. doing a blowthrough on my 86 F-150.

The box i've come up with so far is 24 cubes.

6 sealed
18 ported
45 hz
8 inches high 30 inches wide port

 

I've messed around a lot with the graph on winisd and it seems to keep showing positive gains the bigger the box but I wonder if 24 cubes is too big for 2 18's in a 4th on ~2k? Any insight would help especially if you've done a few 4th orders

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1 minute ago, bmwking said:

i know literally nothing about the dynamics of 4th orders, but holy shit 24 cubes seems wayyyyy too big for those subs.  so i guess im commenting out of curiosity to see what answer you get :)

Yeah I've seen a lot of people say you for the recommended sealed then a common ratio is 3:1 CT sounds says to seal em at 5 cubes each so that would be a 10 sealed 30 ported but I know 40 cubes is gotta be too fkn big.

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I'd do 10 sealed, 20-22 ported. Your port area looks about right though. Your lows come from that sealed section, remember that. Ported section controls roll off mostly and bandwidth. Any way to get the port to have more height and less width, I.E. getting the aspect ratio closer to a 1:1 range? I'm not saying exactly 1:1, as I know this is s blowthrough, but maybe 2:1? Something like 10X24" or 12X20"? Willing to bet it would behave better with a port like I suggested rather than the port you ran numbers on. I don't know if modeling software would tell you a gain or not, but the real world testing tells me you would likely gain with ratio closer to what I suggested.

Im not the one you want to try to troll. Just a fyi for you.

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Here's some modeling results for the CT tropo 18's: 

Ported 12 cubes @35 Hz (orange plot)

4th Bandpass  rear: 6 net front 18net @ 45Hz (red plot)

image.jpg

*power shown is per driver.

Just for your reference, ported looking good for it's small size.

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On 10/7/2018 at 4:54 AM, CleanSierra said:

I'd do 10 sealed, 20-22 ported. Your port area looks about right though. Your lows come from that sealed section, remember that. Ported section controls roll off mostly and bandwidth. Any way to get the port to have more height and less width, I.E. getting the aspect ratio closer to a 1:1 range? I'm not saying exactly 1:1, as I know this is s blowthrough, but maybe 2:1? Something like 10X24" or 12X20"? Willing to bet it would behave better with a port like I suggested rather than the port you ran numbers on. I don't know if modeling software would tell you a gain or not, but the real world testing tells me you would likely gain with ratio closer to what I suggested.

Only real reason I decided on 8x30 is because I liked the idea of a wider port firing into the cab aesthetically but I could easily go as high as about 14 inches.

 

Yours does show way more gains on winisd then mine, winisd seems to infinitely show gains the bigger the box or up to 40 cubes at least. Also a nice lower tuning on the sealed portion @ 10 sealed.

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On 10/7/2018 at 5:30 AM, Joe X said:

Here's some modeling results for the CT tropo 18's: 

Ported 12 cubes @35 Hz (orange plot)

4th Bandpass  rear: 6 net front 18net @ 45Hz (red plot)

image.jpg

*power shown is per driver.

Just for your reference, ported looking good for it's small size.

Thanks for taking the time to graph that, do you mean a standard ported box? I don't think I can do that in my truck because If I cut high enough for the subs to point into the cab I'll be just about touching the glass, thats why I was going for a standard 4th order blowthrough.

 

If they were 15's I'd probably just go with the kinda half-blowthrough ported design though. Only seen a few people run it but it seemed to workout great for them.

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8 hours ago, DirtyDuzit said:

Only real reason I decided on 8x30 is because I liked the idea of a wider port firing into the cab aesthetically but I could easily go as high as about 14 inches.

 

Yours does show way more gains on winisd then mine, winisd seems to infinitely show gains the bigger the box or up to 40 cubes at least. Also a nice lower tuning on the sealed portion @ 10 sealed.

I like to have as big in the sealed section for lows, as long as power and mechanical handling of the sub can take it. 

Im not the one you want to try to troll. Just a fyi for you.

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