i am still trying to understand how a port on a speaker box works but i now realize that it doesnt make any difference if the port is inside or outside of the box just as long as the port starts close to the speaker. true? not true?
i am wondering if i can route the port out the back of the speaker box to the outside of the car then come back inside? this might sound like a goofy idea but i think this would actually save me a lot of space and the vehicle i am working on it wouldnt like completely ridiculous at all.
i know how crazy this sounds but i am quite serious about doing it. i have enclosed an artists rendering hehehe
i am wondering if i can route the port out the back of the speaker box to the outside of the car then come back inside? this might sound like a goofy idea but i think this would actually save me a lot of space and the vehicle i am working on it wouldnt like completely ridiculous at all.
i know how crazy this sounds but i am quite serious about doing it. i have enclosed an artists rendering hehehe
How long is this port? Your 'artists rendering' =D makes it look like it's about 8 feet long. Try altering the port dimensions in order to get it shorter, unless you're trying to fit the sub to a smart car there should be plenty of room for a port.
As far as I'm aware it doesn't matter if the port sticks out or in, it forms a resonant system with the box, just most of us don't want our sspeakers looking like elephants. The problem is the port does act like a delay line, it'll take time for the pressure wave to go from the back of your speaker all the way round your car in the tube lol.
In short keep the port short
and you should have no troubles
As far as I'm aware it doesn't matter if the port sticks out or in, it forms a resonant system with the box, just most of us don't want our sspeakers looking like elephants. The problem is the port does act like a delay line, it'll take time for the pressure wave to go from the back of your speaker all the way round your car in the tube lol.
In short keep the port short
and you should have no troubles
Funniest pic I've seen all day! How about using that for your avatar?
Seriously though, putting the port outside the box is no problem but that pipe looks much too long for reflex loading.
Even if the box tuning looks right by a simple calculation, if the pipe's longer than about a foot, you'll have nasty pipe resonances starting right down in the bass.
You could do a transmission line or horn design like that though.
Oh no - now I've got a picture in my head of what a bass horn would look like stuck on top of the cab, firing in through the roof!
As long as you remember that the area of the port must go up with length, you'll notice that the area will have to be huge.
The idea of a port is to link the inside of the box with the rest of the world. It can stick out of the box, but that's rarely a good idea, as it's more likely to get bashed etc.
Generally speaking, they protrude into the box. While taking up a little box volume, it's better than having a huge extension to the box that you must keep air tight (ie, no leaks in the port.
Question - why do you want the port next to your head? There's no need for it to be there, unless you're after some kind of subsonic hairdryer... (wait, that sounds cool - I want ot try that.)
Chris
The idea of a port is to link the inside of the box with the rest of the world. It can stick out of the box, but that's rarely a good idea, as it's more likely to get bashed etc.
Generally speaking, they protrude into the box. While taking up a little box volume, it's better than having a huge extension to the box that you must keep air tight (ie, no leaks in the port.
Question - why do you want the port next to your head? There's no need for it to be there, unless you're after some kind of subsonic hairdryer... (wait, that sounds cool - I want ot try that.)
Chris
yea, agree... the "mr. bill" pic caught me funny too.
Bandpass boxes in standard cab minitrucks beds, with the ports firing into the cab was quite popular at the local army base... The key was a flex rubber duct from the bed to the cab, to deal with frame flex. Never did a horn that way though... hmmm....
Bandpass boxes in standard cab minitrucks beds, with the ports firing into the cab was quite popular at the local army base... The key was a flex rubber duct from the bed to the cab, to deal with frame flex. Never did a horn that way though... hmmm....
That's why you get an extended cab!
An externally hosted image should be here but it was not working when we last tested it.
Yeah you can put the port outside - but it won't augment the inside LF at all... AND you had best have a wadfull of $$ to pay off those tickets!! Wheeeee!
_-_-bear
EDIT: oh wait a sec, you want to run the port outside the car and back IN? sure... but then it is mostly a TL (transmission line). Cool, do it in chrome, baffle the passersby...
_-_-bear
EDIT: oh wait a sec, you want to run the port outside the car and back IN? sure... but then it is mostly a TL (transmission line). Cool, do it in chrome, baffle the passersby...
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the port doesnt need to be that long i just put it in the picture to show that i wouldnt have any restriction on length. i had another DIY guy help design me a box and i am building it to his specs.
"6.2 ft^3 tuned around 27-28 Hz with an 8" diameter vent 23-24" long"
thats a huge port. and i figure any space help i can get will leave me space to possibly run a 3rd or 4th sub woofer. ideally i would like to make a box that is as narrow as possible and just really tall
the first picture was just an idea i had but i can also build a shorter port like this new and improved artists rendering. the port doesnt have to be directly over my head it can be placed in the center of the truck or wherever thats what is so great about this idea. as long as i am allowed to leave the truck with the port and come back in again i think im golden!!
whats a transmission line?
bp im all for your idea of building a horn like that but try and fit 4 of them in your truck, so far the this is the best idea i have come up with.
"6.2 ft^3 tuned around 27-28 Hz with an 8" diameter vent 23-24" long"
thats a huge port. and i figure any space help i can get will leave me space to possibly run a 3rd or 4th sub woofer. ideally i would like to make a box that is as narrow as possible and just really tall
the first picture was just an idea i had but i can also build a shorter port like this new and improved artists rendering. the port doesnt have to be directly over my head it can be placed in the center of the truck or wherever thats what is so great about this idea. as long as i am allowed to leave the truck with the port and come back in again i think im golden!!
whats a transmission line?
bp im all for your idea of building a horn like that but try and fit 4 of them in your truck, so far the this is the best idea i have come up with.
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a 2 foot long port wont be long enough to go out of the car and in again. Also if you don't know what a tranmission line is don't attempt it, especially if you're cutting holes in a car for it, try it out in the shed first or something.
Also a heads up as Godfrey said long ports i.e. longer than a foot 'you'll have nasty pipe resonances starting right down in the bass' and bass horns are HUGE. Like meters across, a funny thought for a car but you'd have to replace your roof with the horn lol
In short keep it simple and dont go overkill. btw what drivers you looking at using?
Also a heads up as Godfrey said long ports i.e. longer than a foot 'you'll have nasty pipe resonances starting right down in the bass' and bass horns are HUGE. Like meters across, a funny thought for a car but you'd have to replace your roof with the horn lol
In short keep it simple and dont go overkill. btw what drivers you looking at using?
i suppose anything is possible and i am even considering a different sized box and port. i am building to those specs but im still not too sure why yet. i just know that the guy who made them for me knows what he is doing.
ideally i would like to use a smaller box instead of cutting holes all over my work truck.
yes i would consider keeping the port inside but i would really like to keep as much space inside the cab as possible.
ideally i would like to use a smaller box instead of cutting holes all over my work truck.
yes i would consider keeping the port inside but i would really like to keep as much space inside the cab as possible.
the speakers i am using is kicker L7 12" the square ones. i would like to fit 4 of them into my truck. i have a bunch of jbl bp1200.1 to drive them.
the speaker box could be right against the roof. im sure i could get the port out across the roof then back inside again. if i do figure out a way to get 4 of these boxes in there then it will be 4 ports that are 8 inches across and 2 feet long. it seems like a lot of wasted space especially when i can put them outside.
i havent cut any holes yet im still just thinking about doing this. in reality ill probably just get stuck using 2 speakers instead of 4.
the speaker box could be right against the roof. im sure i could get the port out across the roof then back inside again. if i do figure out a way to get 4 of these boxes in there then it will be 4 ports that are 8 inches across and 2 feet long. it seems like a lot of wasted space especially when i can put them outside.
i havent cut any holes yet im still just thinking about doing this. in reality ill probably just get stuck using 2 speakers instead of 4.
Hi there: Try googling-up passive radiator, go to the Wikipedia article for a basic discription and then for more technical information try the next article, The Subwoofer DIY page, Passive radiator systems. Vance Dickason's book Louadspeaker Design Cookbook,7th ed, available from Parts Express has Chapter 3, pages 85 through 92 on passive radiator syatems. regards, Michael
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