Turning a Sealed Box Into a Vented Box

[ViperJ]

As the title states I would like to turn my sealed box into a vented box. I dont have the exact specs with me right now but would happen if I was to drill a 2inch. hole into each chamber of the subs? Would the bass be louder or would it make it sound worse? Btw they are 10" MTX Thunder 4000 subs if you need this info. Thanks

[alphalanos]

it all depends on the air space requirement for the subs. usually sealed boxes are smaller than ported. chances are just making two ports on your box will make it sound like crap. leave it the way it is, and if you really want to try ported, look up your subs required airspace and buy a proper box. it wont sound good unless the box is right. the port has to be a certain length, width, and it needs to be flared on the end to reduce air noise. also a sub in a ported box cannot handle as much power as it could in a sealed box due to the high amount of air spring in a sealed vs. low amount in ported.

[sr20de4evr]

you would need to cut a hole and put in a port, and chances are your box is WAY too small to port properly. Ported boxes have to be bigger to begin with, plus you have the port sitting inside taking up airspace, so they need to be even bigger. An optimal ported box is normally about twice as big as an optimal sealed box for the same sub (after all displacements and everything). So no, I wouldn't try it. You would most likely end up ruining your box and ending up with a POS that sounds like complete ass.

[sr20de4evr]

Originally Posted by alphalanos

it all depends on the air space requirement for the subs. usually sealed boxes are smaller than ported. chances are just making two ports on your box will make it sound like crap. leave it the way it is, and if you really want to try ported, look up your subs required airspace and buy a proper box. it wont sound good unless the box is right. the port has to be a certain length, width, and it needs to be flared on the end to reduce air noise. also a sub in a ported box cannot handle as much power as it could in a sealed box due to the high amount of air spring in a sealed vs. low amount in ported.

looks like I got beat to the punch

you're mostly right, except for the end. Ported subs can handle more power than sealed (at least mechanically), not less. There is actually more pressure change ("air spring") inside a ported box than in a sealed box, which is why the cone moves less on the same power in a ported box. Of course this all applies within half octave below tuning and a full octave above tuning, below this range a ported sub will start unloading and have MUCH higher excursion than sealed, and above this range the excursion will be similar between ported and sealed.

[alphalanos]

i thought in ported applications the sub has a greater chance of over excursion

[sr20de4evr]

only if it starts unloading, which happens below a half octave below tuning. So if your box is tuned to say 28hz, the sub won't start unloading until ~20hz. Since VERY little music has information below 20hz, chances are with a 28hz box you would always have equal or less excursion than sealed (the equal being at ~56hz and higher). But if you had say a 45hz box, it would start unloading at ~32hz, since a lot of music has information in the high 20's and low 30's, there's a very good chance you would end up overexcurting the sub if you didn't have a subsonic filter (a ssf is a simple highpass filter at a very low frequency, it's there to cut the power going to the sub at low frequencies to keep it from unloading below tuning).

[PaulD]

I always thought a sealed box handled the most power ..... ported doesn't need as much, since it is a little more efficient

[bumpinstang77]

You get what's called damping factor with the port.... ever notice that a sub BARELY moves at tuning but still sounds very loud......The bigger the port the less it will move around tuning..... but like sr20 once it starts moving again its high enough frequencies to where thesub naturally doesn't move much anyways so really it moves a lot less then sealed....... Ever wonder why there's only a few xxx vids of it moving very much yet you can obviously tell the impact it has??? XXX's are wierd about low excursion in ported boxes......they still slam though.

[sr20de4evr]

Originally Posted by PaulD

I always thought a sealed box handled the most power ..... ported doesn't need as much, since it is a little more efficient

ported doesn't need as much power to get as loud as sealed because it's more efficient, but a ported sub within about an octave of tuning can still handle more power than sealed (resulting in even MORE output).

I guess the best illustration is with home speakers, preferably vented towers where you can actually see the speakers themselves. Play a few different test tones at the same volume and watch the cone's excursion. Find the frequency where the cone moves the least, it should be around 30-45hz with most decent towers, and turn up the volume a resonable amount. While playing the sine wave, take a book or something and cover up the port and watch what happens to the cone, it starts moving a helluva lot more than before and the spl drops significantly, and if you remove the book it goes back to barely moving and the output rises back to where it was.

[bumpinstang77]

yulp lol...... I do that with my subs on late night tip.... that bottom note is down around 30hz so they don't move a whole hella lot but I cover up that port and WOAH easily over 2" p2p

[CBFryman]

or you give it enough power to get 2" p2p and then cover the ports...oops....speaker go bye bye

[bumpinstang77]

nah.... I don't think they're a bottomless design but I will never have enough power to bottom them out unless under tuning.