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IndianaBassHead

4th order blow-through build help, 6 18's

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What's up guys? I bought a 99 ford f-350 powerstroke long bed dually over the weekend and I am ready to get my install going. I have never built a 4th order before so any help is appreciated. The equipment will be (6) obsidian audio 18's running on a crecendo 3500 for now. The subs will be in the bed of the truck with the port in the back window. Basically like John Hone's truck build.

What I am planning now is having the subs firing up. Would there be any issues with this as opposed to firing forward? Also, What ratio would you recommend since I have all the airspace I need. With the tuning, I was thinking around 48 hz but I really want to be able to hit the low lows so I'm not sure what would be ideal.

One last question, with the 4th orders, what is the ideal port area per sq ft? would 16 in be fine?

Like I said, any help is appreciated as this is my first bandpass. And I will for sure post build logs! :drink40:

Edit: Forgot to mention, There will be a camper shell that is sealed of course.

Edited by BanginHoe92

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What's up guys? I bought a 99 ford f-350 powerstroke long bed dually over the weekend and I am ready to get my install going. I have never built a 4th order before so any help is appreciated. The equipment will be (6) obsidian audio 18's running on a crecendo 3500 for now. The subs will be in the bed of the truck with the port in the back window. Basically like John Hone's truck build.

What I am planning now is having the subs firing up. Would there be any issues with this as opposed to firing forward? Also, What ratio would you recommend since I have all the airspace I need. With the tuning, I was thinking around 48 hz but I really want to be able to hit the low lows so I'm not sure what would be ideal.

One last question, with the 4th orders, what is the ideal port area per sq ft? would 16 in be fine?

Like I said, any help is appreciated as this is my first bandpass. And I will for sure post build logs! :drink40:

Edit: Forgot to mention, There will be a camper shell that is sealed of course.

Demo when done, first!

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What's up guys? I bought a 99 ford f-350 powerstroke long bed dually over the weekend and I am ready to get my install going. I have never built a 4th order before so any help is appreciated. The equipment will be (6) obsidian audio 18's running on a crecendo 3500 for now. The subs will be in the bed of the truck with the port in the back window. Basically like John Hone's truck build.

What I am planning now is having the subs firing up. Would there be any issues with this as opposed to firing forward? Also, What ratio would you recommend since I have all the airspace I need. With the tuning, I was thinking around 48 hz but I really want to be able to hit the low lows so I'm not sure what would be ideal.

One last question, with the 4th orders, what is the ideal port area per sq ft? would 16 in be fine?

Like I said, any help is appreciated as this is my first bandpass. And I will for sure post build logs! :drink40:

Edit: Forgot to mention, There will be a camper shell that is sealed of course.

Demo when done, first!

for sure if you come to Indiana lol. but does anyone have any input to give me?

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Oh thought you lived in nj.

& I'm not 100%, with 4ths so ill be quiet & wait for the build log

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there wouldn't be any issues firing them up, just make sure you can get enough height to get a good ratio. a minimum 1:2 ratio. double up on wood all the way around, make the port removable so you can play with tuning and port area. port area isn't related to volume. shoot for about 880 sq inches of port, then you can adjust port area and tuning from there.

i'm coming up with numbers of about 24 cubes sealed net, and for a 1:2 ratio, 48 cubes ported net.

hope you have the space for this haha. this thing is gonna be huge.

also, PM me once you get some numbers for this. I'd be glad to sketch it up for you :)

Edited by 412 CVX

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Hey man, I built the truck in the video I am including in your thread. Many people told me not to do subs up with port forward, but it honestly worked out great in this truck. I won't lie one bit about one aspect....the truck falls flat on it's face if the windows are up and doors are shut...only does a 52-53 from 32-47 Hz.....as soon as you roll the windows down though, this thing instantly jumps to a 56- 57......it's crazy as hell.

All of that being said, I went with right around 2.8 cubes net sealed per woofer and then the ported chamber is right around 22 cubes net with 310 square inches of port. Obviously this is not the biggest ratio, but it worked out great for this truck. With 4th order alignments, it's safe to say most folks go with a 2:1 ratio (ported to sealed). It would also be my suggestion to stay somewhere between 14-18 square inches of port per ported cube and a tuning of 46-51 Hz. The best advice anyone can give you on the ported chamber is to start with the largest port possible and then start testing/shrinking/testing/shrinking from there until you begin to lose Db's.

I would also encourage you to read through this thread on CACO for further information. The thread is super long, but there's lots of great information in there about 4th order alignments.

http://www.caraudioclassifieds.org/forum/general-car-audio-discussion-questions/123066-4th-orders-why-some-people-so-quiet-them.html

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there wouldn't be any issues firing them up, just make sure you can get enough height to get a good ratio. a minimum 1:2 ratio. double up on wood all the way around, make the port removable so you can play with tuning and port area. port area isn't related to volume. shoot for about 880 sq inches of port, then you can adjust port area and tuning from there.

i'm coming up with numbers of about 24 cubes sealed net, and for a 1:2 ratio, 48 cubes ported net.

hope you have the space for this haha. this thing is gonna be huge.

also, PM me once you get some numbers for this. I'd be glad to sketch it up for you :)

thanks for the help! I appreciate it. I will take some measurements tonight after i get off work. That thing will probably fill up the whole truck bed!! But I will pm you once I come up with measurements and we can go from there. May have to switch to 15's. But I get off work at 11 pm est and I'll measure then.

Hey man, I built the truck in the video I am including in your thread. Many people told me not to do subs up with port forward, but it honestly worked out great in this truck. I won't lie one bit about one aspect....the truck falls flat on it's face if the windows are up and doors are shut...only does a 52-53 from 32-47 Hz.....as soon as you roll the windows down though, this thing instantly jumps to a 56- 57......it's crazy as hell.

All of that being said, I went with right around 2.8 cubes net sealed per woofer and then the ported chamber is right around 22 cubes net with 310 square inches of port. Obviously this is not the biggest ratio, but it worked out great for this truck. With 4th order alignments, it's safe to say most folks go with a 2:1 ratio (ported to sealed). It would also be my suggestion to stay somewhere between 14-18 square inches of port per ported cube and a tuning of 46-51 Hz. The best advice anyone can give you on the ported chamber is to start with the largest port possible and then start testing/shrinking/testing/shrinking from there until you begin to lose Db's.

I would also encourage you to read through this thread on CACO for further information. The thread is super long, but there's lots of great information in there about 4th order alignments.

http://www.caraudioc...quiet-them.html

alright, i will check out that thread. Thanks for the help! I can't view videos while I'm at work but I will check it out tonight. I'll post updates tonight with measurement specs.

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Hey man, I built the truck in the video I am including in your thread. Many people told me not to do subs up with port forward, but it honestly worked out great in this truck. I won't lie one bit about one aspect....the truck falls flat on it's face if the windows are up and doors are shut...only does a 52-53 from 32-47 Hz.....as soon as you roll the windows down though, this thing instantly jumps to a 56- 57......it's crazy as hell.

All of that being said, I went with right around 2.8 cubes net sealed per woofer and then the ported chamber is right around 22 cubes net with 310 square inches of port. Obviously this is not the biggest ratio, but it worked out great for this truck. With 4th order alignments, it's safe to say most folks go with a 2:1 ratio (ported to sealed). It would also be my suggestion to stay somewhere between 14-18 square inches of port per ported cube and a tuning of 46-51 Hz. The best advice anyone can give you on the ported chamber is to start with the largest port possible and then start testing/shrinking/testing/shrinking from there until you begin to lose Db's.

I would also encourage you to read through this thread on CACO for further information. The thread is super long, but there's lots of great information in there about 4th order alignments.

http://www.caraudioc...quiet-them.html

Was looking at that thread and another question came up.. Do you think I would be just as loud if not louder doing 4 OA 18's with a 3:1 ratio instead of 6 with a 2:1? If so, that would be a lot easier to build and would save me a little cash.

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If you can get a 3:1 ratio, then potentially. Could give you a more definitive answer with dimensions.

4 18's - 3:1 ratio 16 cubes sealed 48 ported

6 18's - 2:1 ratio 24 cubes sealed 48 ported

6 15's - 2:1 ratio 15 cubes sealed 30 ported

6 15's - 3:1 ratio 15 cubes sealed 45 ported

these are just arbitrary numbers. depending on how much power you plan on giving the woofers down the road, these numbers may get smaller or bigger.

Edited by 412 CVX

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6 18's in a 4th is huge lol im not sure what you mean by the box design. Do you have any pics to help me understand and if you want lows tunning will play a part so id say lowest tunning to go for is 44hz but its mostly in the sealed chamber. Make a bigger sealed chamber and you have to go with a 2:1 minimum you can go less if needed. The higher the ratio the more spl and less bandwidth

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