Porting Subwoofer Boxes...Good, Or bad? and effect?

Question

I was looking at a set of subwoofers that are 15" and put out a 750 RMS. I wanted to know why they recommended A sealed Box and not ported. Because i thought porting it makes it sound better and lets the air flow. But what do i know haha

Answer 1

Here are some tips:

http://spkrbox1.spaces.live.com/

Answer 2

First subs are designed by the manufacture to work best in a sealed box, ported box or both types of boxes. So find out what type of box the subs are designed for. Air flow is only relevant to the type of woofer. Sub don't put out power, amlifiers do, subs have a power handling.

Ported boxes can be smooth but are usually designed to boom in cars. They tend to be more efficient, therefore louder with less power.

Sealed boxes are usually smoother. They usually play deeper than a ported box (explained below). The bass is usually tighter and the box is easier to build. Sealed speaker/box combos are usually a little less efficient than ported.

A port gives a 3db or so boost to the frequency it is tuned too. The down side is that the frequency response tends to roll off sharply after the frequency the port is tuned to. For example if you tune your port to 60Hz then the volume of frequencies below that will decrease more rapidly than if it were a sealed box
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The frequency a port is "tuned" to is based on the volume of the box and the size of the port, dia and length. It is easiest to go with a box/port suggested by the manufacturer. However if you have all of the speaker spec.'s and the software you can design it yourself. So if you want a boom you would tune it to a frequency that is already fairly loud. If you want a smoother bass then tune the port to the point where the woofers low end frequency hits the -3db point. This will help extend the lower end of the sub.

After years of box building I tend to put large woofers in the smallest sealed box I can and have gotten away from porting. Sealed boxes almost always sound better for smooth, clean, tight, low, bass.


Two examples:

Two 10's each in a 3/4 cubic foot box and one 15" in a 3 cubic foot box, all sealed and stuffed with poly fill. This covers the full low end perfectly. The 10's covered the mid bass and hit hard. The 15 went low and still responded quickly with out mudding up the low low frequencies.

Second Example with less space available. One 12" in a 2 cubic foot sealed box stuffed with poly fill. A bigger woofer will generally play lower than a smaller one and a smaller box will generally play smoother but sacrifice some low end. So the biggest woofer in a smallish box is a compromise I found works best.

both boxes were based on manufactures suggested ranges.

So in general if you want smooth clean tight deep bass, go for sealed. I don’t want to steer you away from ported you just need to do your home work first and really think about what kind of sound you want.

If you have the time and specifications to design and build (or buy premanufactured) and want booming, loud, bass go for ported. You can get great sound out of ported but you have to design it that way.

Answer 3

I dont know much and would get a few other opinions on it too...

but i have heard that ported boxes sound smoother and are better on the sub itself since the air wont be compressed and pushing back on the woofer to get out of the box.. but a non ported box thumps louder and can be heard more and is alot harder on the sub, a smaller amp and durable sub is what i would reccomend for that

Answer 4

if the specs called for sealed it's to maintain a particular sound from the subs. whenever you port your box you automatically turn that sound into a deep booming sort of bass. sealed boxes are primarily for very tight crisp bass like in jazz or pop rock. porting is more for rap or rock that have really deep thunderous bass. you can go either way and it also depends on what sort i.e. type or brand of subs you have also.

Answer 5

they way the subs were designed makes them sound best in a "controlled" box. Some sub designers shy away from non sealed boxes because of the complexity of the deign requirements. Sealed boxes sound the cleanest by far but not the loudest. if u goto http://www.jlaudio.com and read up one sub box designs u will get a real good understanding of subs and box designs.