Faithless
Subwoofers in ICE can be incorporated in different types of enclosures
sealed,ported and bandpass ( a compination of sealed and ported where you cannot see the sub at all)
now a 12inch driver can either be put in a box that is sealed or a box that has a port ( basically a hole)
Sealed subs require more power(amp power) to be driven and give a tighter response.
Sealed box designs and single-reflex bandpasses are much better at controlling excursion at extremely low-frequencies (below 30Hz.) For this reason, they can usually handle more power in these frequency ranges than ported designs and dual-reflex bandpass designs which makes them less prone to low-frequency induced speaker damage. At frequencies below the tuning frequency of the port, a woofer in a ported box (or a dual-reflex bandpass) starts to de-couple
Sealed enclosures and single-reflex bandpass designs have a rather shallow low-frequency roll-off rate of around 12dB/octave, whereas ported enclosures and dual-reflex bandpasses typically exhibit 18- 24dB/octave roll-off
Ported subs are more efficient ,bass in these subs is slightly extended
A ported enclosure can also achieve good transient behavior but never as good as an optimized sealed enclosure. It is possible, however, for a well-designed ported enclosure to have better transient response characteristics than sealed enclosures with higher Qtc's (above 1.0.)
This low-frequency reinforcement is one of the big advantages of a well-designed ported system.
The other big advantage is that the interaction of the port, the enclosure and the speaker's resonant characteristics also reduces cone motion and, therefore, distortion at higher volume levels in the frequency range controlled by the port
Good sq may be found in both however it is difficult to build a ported box since it involves precise calculations to get the volume right.
Also the port design depends on port tuning frequencies which takes time an experience to master , hence a sealed sub is better if you are going to build the box yourself(or you are doing it from a roadside installer)
Also a ported box will be larger than a sealed one
HOwever if you are buying a ready made ported box from a manufactureer like JBL then you will find these to be more efficient
NOW A bass tube is nothing but a ported sub so expect all charecteristics of a ported box
JBL bass tubes are affordable and well built for 5-6k(grey)
the advantage of these tubes is the space they take in a car(sedan).
their form allows you to fit it in the boot against the angled back seat which is useless space anyway!
also these are easy to remove when you need more luggage space!
In car audio your choice of box depends on the music you hear and the amp power you will use
i have seen that most times people like toplay it loud and like that puonding bass ( its more important to them in a car) and hence they tend to go ported
general rules
if your amp is small - go ported
if you like house,hip hop and trance - go ported
Also note sumoku have an internal amp ( active subs ) but i would not recommend them at all for various reasons
Also note - though it is possible to connect a sub directly through the HU of a car i dont know anyone who has ever done this!! and i will be shocked to know if anyone has!
You should know that subs are genrally rated upwards of 200rms, now a car HU (pioneer/alpine) supplies only 22rms/channle ( all that 50rms you see is a load of bull) this is hardly enough to move your sub at all.
Please do buy an amp for ANY sub (even if its ported!)