Full Version: How to make adjustable slot ports
Well as the title suggests, im looking at making a new ported box for the sub in my sig. basically i'm wanting to make a box with an adjustable slot port so i can use it for SPL and everyday driving. Basically for everyday stuff im gonna tune it to ~27hz and ~45hz for SPL. the box will be 4.15cuft before the port. can sum1 tell me how to do the adjustable port??
Well first make the port the required lenth and height width for the SPL tuning.
If the slot port is say 4inchs wide when tuned at 47hz then when tuned to 27hz the port width would be like 2inchs.
So you just get a sheet of 36mm MDF and slot it into the port making the area less. You could then have two or three screws to hold it into place.
pretty easy.
If the slot port is say 4inchs wide when tuned at 47hz then when tuned to 27hz the port width would be like 2inchs.
So you just get a sheet of 36mm MDF and slot it into the port making the area less. You could then have two or three screws to hold it into place.
pretty easy.
how are you going to screw the 36mm piece on? the port is 2in wide, hard to fit a scre driver in that space. if you screw from the top, then chances are you'll get vibrations as the piece of wood is tapping against the spl port and that could really suck for music. also if you screw from the top then you are left with holes in the spl port...
the way i'd probably do it is to make the port height shorter. goto clark rubber and get a big piece of foam and wedge it down the bottom of the slot port
the way i'd probably do it is to make the port height shorter. goto clark rubber and get a big piece of foam and wedge it down the bottom of the slot port
And aren't you going to get a hell of alot more port noise with a port that's half as wide (half the cross-sectional-area)?
Bah..
Make it so u can completly remove the port and put a different one in like Andu's!!
Thats what im doing..
Spl port and Daily port..
Make it so u can completly remove the port and put a different one in like Andu's!!
Thats what im doing..
Spl port and Daily port..
yeh, but that is not a slot port that is a rectangular port
well said rippedskin
"emphasis on RIPPED"
"emphasis on RIPPED"
My Bad i didnt notice it said slot port..
It still could be done but ud have to be presice at cutting it and u cant seal it! LoL
It still could be done but ud have to be presice at cutting it and u cant seal it! LoL
QUOTE
Originally posted by N.O.S Boy:
Bah..
Make it so u can completly remove the port and put a different one in like Andu's!!
Thats what im doing..
Spl port and Daily port..
Yep.. Make it completely removeable..
Bah..
Make it so u can completly remove the port and put a different one in like Andu's!!
Thats what im doing..
Spl port and Daily port..
I think I may have built my box backwards...
I built it so in standard form, it's tuned to 45Hz, SPL. If I reduce the internal volume then that will increase the res. freq., and if I lengthen the port while keeping it the same CSA then that will lower my res. freq. Only thing is that if I reduce CSA so I don't have to lengthen the port as much, I would get port noise... I need to add another 8-10 inches of port length and reduce CSA to get it tuned to the res. freq. I want... If I keep it the same CSA then I need to lengthen the port by quite a fair bit more (not calculated yet but I know it would be ridiculously long!)
I built it so in standard form, it's tuned to 45Hz, SPL. If I reduce the internal volume then that will increase the res. freq., and if I lengthen the port while keeping it the same CSA then that will lower my res. freq. Only thing is that if I reduce CSA so I don't have to lengthen the port as much, I would get port noise... I need to add another 8-10 inches of port length and reduce CSA to get it tuned to the res. freq. I want... If I keep it the same CSA then I need to lengthen the port by quite a fair bit more (not calculated yet but I know it would be ridiculously long!)
Hmm have thought about this before and have come up with this... dunno if this will help but should work say if you want two port variations with a fixed port area.
Basically if you have a port using 3 sides as part of a box you can create a flap/extension to the port that can be hinged inside the box like in the following pic:
So when you want a longer or shorter port you just flip the flap ... provided the port is big enough and arm long enough flip it.
To secure the flap at either of the positions you can maybe just screw through the box into the flap to hold it. If you make accurate MDF cuts the problem of air leaks between the port and the box should be minimal. Though I doubt they would make a drastic difference anyway?
As for the unused screw holes you can just plug them with screws... but I'm sure you can think of other elegant means.
Well that's the basic theory... you can maybe even if you want use some sort of acutator to do the hinging action for you or improve on it... but this is just one of the ideas for an adjustable port that have popped up in my head.
[ February 03, 2003, 05:17: Message edited by: splbound ]
Basically if you have a port using 3 sides as part of a box you can create a flap/extension to the port that can be hinged inside the box like in the following pic:
So when you want a longer or shorter port you just flip the flap ... provided the port is big enough and arm long enough flip it.
To secure the flap at either of the positions you can maybe just screw through the box into the flap to hold it. If you make accurate MDF cuts the problem of air leaks between the port and the box should be minimal. Though I doubt they would make a drastic difference anyway?
As for the unused screw holes you can just plug them with screws... but I'm sure you can think of other elegant means.
Well that's the basic theory... you can maybe even if you want use some sort of acutator to do the hinging action for you or improve on it... but this is just one of the ideas for an adjustable port that have popped up in my head.
[ February 03, 2003, 05:17: Message edited by: splbound ]
It could work.. Also I think hardon posted a similar idea in another thread a few days ago..
Just make a foam port plug to throw into the port for daily driving and lower tuning.
Pull it out for higher tuning and comps, people have been doin' it for years,
port noise you say??, I couldnt hear any.
Pull it out for higher tuning and comps, people have been doin' it for years,
port noise you say??, I couldnt hear any.
my slot port is 6 inch wide and 8.5 inch deep .. right ... now it's tuned to 60 hz .. but it's no good for normal music .. if i oput a peace of MDF ova half of the port ... to make it a 3 inch slot port .. would this make it sound betaa or worse
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