# what port size eh?



## pete? (Jul 6, 2004)

well i think i may want to port my sub box..i dunno, but i figure i can port it and if i dont like it i can simply seal it back up. i have an alpine type-E sub and a Q-logic type-2 medium sized box (mine dosent look like that but it is a type-2 medium, they wouldnt change the size of the box with a new model would they?) my box comes with a port and all i need to do is cut it to lengh.


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## Matt93SE (Sep 17, 2003)

Why do you want to port it?
If you're having sound quality problems in a sealed box, then the ported box will really make it worse...

If you're looking for that extra couple dB of output, then it will help.. but I suggest you get the exact volume of the box by measuring it INTERNALLY and then do some math on it before you start to mess with the port stuff.


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## pete? (Jul 6, 2004)

i was kinda just curious about how it would sound/affect the sound. i built my entire system with $500.........yea SQ is a problem lol. but the box allready has a cut out for the port and has a cap or a "cork" if you will so if it sounds like crap i can just put it back to normal. and i figured i have gotten alot of help from all the audio gurus here before (i love music and SQ but audio confuses the hell out of me  ) i would get some more :cheers: thanks


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## captain_shrapnel (Sep 10, 2004)

Pete, porting a sealed box is gonna mess everything up worse. A sealed box is the least sensitive to internal volume and will tolerate a miscalculation fairly well. A ported box is a whole other beast. You will need a larger box and the port MUST be tuned to the appropriate frequency to match the driver and enclosure. It is VERY touchy. Combo boxes like what you described usually seem to be the wrong size for either application and produce bad sq all around. You need to decide if you really want a ported box, and then build one specifically for your sub. Either check the web for manufacturer's recommendations on port size and enclosure size, or get a box calculator and do it yourself. Also if you go to a ported, don't forget to cut off frequencies below the port resonant frequency or else your sub will think it is in a free air situation and flop like a fish out of water. And remember the cardinal rule: A sub is nothing without its enclosure!


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## pete? (Jul 6, 2004)

on that note never mind. i can normally wing my way through something but the audio stuff is so precise its crazy! thanks alot


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## sfhellwig (Feb 4, 2003)

Per your links the sub wants .6-1.25 ft3 sealed or 1-1.75 ft3 ported. The box you have is internally 1 ft3 meaning that with driver displacement you are less than 1 ft3 sealed. To port this alignment is not within parameters. It could be done for a high tuned db specific alignment but that is all it will be good for. Keeping it sealed puts you in the middle of suggested sealed volumes and using polyfill to stuff it alittle will damp any ringing as well as make it act like a slightly larger enclosure. Last, seal up that port for real. If yours has that silver ring and a cork plug remove them and get a piece of mdf or plywood screwed over it. Leaky sealed boxes can sound worse than mis ported boxes. Otherwise, its build a new box. There are ALOT of pages and online calculators out there that will tell you more than you ever need to know.


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## pete? (Jul 6, 2004)

it dosent have the silver ring what it has is a cut out in the MDF, then it has a plastic plug that fits in and you screw it in place with 1/2in. wood screws and the carpet is over top of it (to port it you need to take the plastic plug out and cut the carpet on top) but like you i didnt trust the seal so what i did when i got it was take the plastic plug out and found my self some (never drying) chulk for windows (its like that putty stuff they use to hang things on walls) and i put a bead of that around the "flange" and i am 100% sure its air tight. im sure the reason im not to happy with the sound is because i have a duel amp (450watt max) and like i have heard cheap amps are on the boomy side. so when ever i get a new car and redo my audio ill be sure to consult with you all so i get the best sound :thumbup: right now im stuck.


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## sfhellwig (Feb 4, 2003)

I would still suggest stuffing the box at least lightly and still covering that hole with wood. If the plastic cap is relatively thin it is flexing and could be out of phase to the woofer. If it is moving a few millimeters it could be considerably messing with the output of the woofer. But that may not be the case. Its up to you if it is too unbearable to try these suggestions.


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## pete? (Jul 6, 2004)

sfhellwig said:


> I would still suggest stuffing the box at least lightly and still covering that hole with wood. If the plastic cap is relatively thin it is flexing and could be out of phase to the woofer. If it is moving a few millimeters it could be considerably messing with the output of the woofer. But that may not be the case. Its up to you if it is too unbearable to try these suggestions.


ill stuff the box sure! could i just use stuffing from an upolstry shop? or is there certain stuff i need to use?


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## sfhellwig (Feb 4, 2003)

1.6pete said:


> ill stuff the box sure! could i just use stuffing from an upolstry shop? or is there certain stuff i need to use?


There is special stuff called Acustuff available at PartsXpress and the likes. It supposedly damps as low as 40hz. I personally couldn't wait and used good old Polyfill from a department store. Only damps to about 60hz but still helps. Roughly a pound per a cubic foot, maybe a little less. Just tease it out and fluff it. Definitely don't do more than this as too much will have an adverse effect.

P.S. If your actually going to an upholstry shop, wool is said to be a wonderful stuffing. Never priced it though.


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## captain_shrapnel (Sep 10, 2004)

Yes, long stranded wool is the best according to The Loud Speaker Design Cookbook, but for your set up I would use fiberglass insulation. Lance Dickason did lots of testing with different fill materials and found that insulation is only slightly worse than wool, and the same as poly fill. Use about 50% fill and don't compress it. Stuffing a box gives it all the good qualities of a larger enclosure while retaining the benefits of a small box.


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