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Sealed, Ported and Distortion

azzfox

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I origionally brought up this topic in a convo with Garfa about Sealed Enclosures being more prone to distortion than Ported Enclosures. Google "Sealed vs Ported" and in every site it will tell you that Sealed is more prone to it.
Why is this? We have had rough stabs at it but cant seem to make any sense of it. Now we are just confused and curious...

Anybody?
 

azzfox

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I am thinking its got to do with sumthing like this: At large volume levels (big excursion) and a quick beat the signal with not match up to the driver due to the push-pull system. eg. if the driver is being pulled back hard and the signal tries to push it forward it will not happen (or not efficiently) and therefore creates distortion.
 

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Hey there mate, just a question. (I'm a bit clueless in this department) Does porting mean cutting a hole in the box? When would you need to port a box? Finally how big should the hole be? (assuming I am correct).

Cheers, and sorry bout all the Q's
Steve.
 

azzfox

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hey, ports arent holes, they are kinda like tubes. to know the right diameter and length you need enclousure designing software like WinISD or Bass Box Pro. you either have a ported enclosure or not. eg. you cannot port a sealed enclousure because ported enclosures are approx twice the size/volume.
 

hakhawk

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porting requires cutting a hle and designing a specific tuned length port, its not just a matter of cutting a hole and stickin a tube in there. i dont know how to setup a ported system, so i just went sealed. too much hassle for something that just gets flogged at cruises and parties.

but one of the more experienced stereo gurus on here should be able to explain it quite well. or just google it.
 

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Ah cheers guys, that sort of explains it, I found some more info that explains the correlation between the volume of the enclosure, the excursion of the sub and the port or tube that is fitted. All together I think you guys pretty much explained the basics for me, cheers.

Steve.
 

garfa

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ok pretty much the box size and the actual volume the port is effects how the frequency curve the sub produces sounds.
the sub will need a box of Xlitres. now this volume is important becausse it will effect how the air internally reacts to the sub moving, but more important in the ration of port size to box size.
this will determine where the frequency curve drops off and also how much the frequency just before the roll off is boosted.
the roll off can be extended but it starts at a higher frequency and also hence removes the boost before the roll off.
 

Matty081

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my theory as to ported vs sealed is that sealed boxes obviously have internal pressure when the sub is vibrating. Consequently the sub cannot "come back" as quick as it should or to quick on the other side of the scale(pressure pushing it out)and doesn't have as much freedom to move. I think it will wear the sub out quicker as well for this exact reason.
I'm always open for correction of course...
 

garfa

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Matty081 said:
my theory as to ported vs sealed is that sealed boxes obviously have internal pressure when the sub is vibrating. Consequently the sub cannot "come back" as quick as it should or to quick on the other side of the scale(pressure pushing it out)and doesn't have as much freedom to move. I think it will wear the sub out quicker as well for this exact reason.
I'm always open for correction of course...
well think about this, with a ported box its easier for the cone to move therefoer the suspension is getting a harder work out. sort of horses for courses really, i dont think there will be a huge difference in the woofers life span depending on the type of box used as long as it is equally suited to both.
 

Matty081

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good point, 6 of one, 1/2 a dozen of the other i guess.
 
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