just a quick question to all you audio geeks can you port any sub or can you olny port portable sub (if there is such a thing) also what does porting do?

Well for starters you port the sub box, not the actual sub.

Any sub can go in a ported box, just some respond better to it than others.

What porting actually does is Tune the box to a particular frequency.

So usually the box will be tuned to the resonant frequency of the car (in SPL comps...correct if wrong..going by faded memory) this will allow the car to act as a resonator and increase the volume and dB reading.

Ported boxes are good if you want SPL (generally, they do have other uses) and sealed are better for overall SQ.

Please be warned Im just being general here as I'm not a car audio nut, I learned enough to get what I wanted out of a system and stopped learning..lol

A good person to ask is Mr_Bob from the Mogwa forums, he's also the NSW Rep for Car Audio Australia www.caraudioaustralia.com

What killbilly said is true except the part about SQ.

In SQ depends on the sub but ported subs can have better SQ than sealed.

Thanks mate, I wasnt quite sure on that..I was just going from a very generalised point of view.

I'll remember that for future ;)

Ported - boxes are usually bigger in size than sealed and have a "tube" (port) that lets some air out of the box. The idea of a ported box is that the speaker port pushes (or pulls) air at the same time as the woofer, reinforcing bass. The box itself acts as an amplifier, yielding to more bass than a sealed enclosure (3 to 4 dB). Ported boxes do not have a linear frequency response. If the box is not built according to specifications, it will not sound good. The box design acts as a filter, cutting off lower frequencies.


An inexpensive subwoofer loaded in the proper enclosure will sound much better than an expensive one in the wrong box. If you choose the wrong type of box for your speaker, the speaker may sound bad or suffer mechanical damage. There are some general rules to help you decide which alignment is the right one for your subwoofers. You need to compare the Thiele-Small parameters of your driver to the guidelines below.

Sealed box (and sealed bandpass) woofers should have the following characteristics:


Qts => 0.40
Fs <= 35 Hz
Xmax => 4 mm

Vented or ported box (and ported bandpass) woofers should have the following characteristics:


Qts <= 0.40
Fs <= 45 Hz
Vas should be relatively low (less than 4 cubic feet unless enclosure size is not a factor).

An additional calculation to help you determine the proper enclosure is the efficiency bandwidth product. This is figured by dividing the Fs value by the Qes value. If the result is close to one hundred, a vented enclosure is the right choice. Closer to fifty means this driver will function best in a sealed alignment.

The best results (widest passband) for bandpass subwoofers are obtained when the Fs value divided by the Qts parameter is ninety or higher.