My experience is limited, which is why I'm asking for more knowlegeable
opinions.  I've owned JL Audio subs and have been very happy with their
performance.  A guy at a "high-end" shop tried to sell me on Image Dynamics.
Checked out their website and they look good on paper...then again most
anything looks good on paper.

I would consider that sub to be a piece of junk then. 1000 watts on a sub is
competition material.
http://www.mtx.com/caraudio/headtohead/w7.cfm

What did they base this foolishness on?  FYI - the JL tech support team is
notorious for not knowing what the hell they're talking about.  Do we have
to go back to that sorry excuse for a tech site at jlaudio.com and tear it
apart again?  :)

Those are the ratings, sure, but they're obviously not accurate because what
you describe above is physically impossible for the kind of consumer grade
components every car audio amplifier manufacturer that I know of uses.  So I
think your best bet would be to tell us which amp you're referring to
specifically.

Why would you suspect that a 12" sub is out of the question for you?

Peter Klein's list of errors:

1. Reason: many subwoofers are made by one of two

2. All the subs with very wide surrounds pay license royalties to

3. Since amplifiers do not

4. A sealed box facing the car behind you will never

5. If the

6. Any woofer of good quality will

/SNIP/

Peter,
   It is evident that you know very little about car audio. Stop now with
your lies and errors.

Who are the two companies that are making so many of the subs on the
market, and which of the big names in car audio are using subs built
by these two manufacturers?

While there *are* subwoofers that are built by one company and sold
under another company's brand name, this isn't the case for any of the
brands that are likely to come up in a serious discussion of "best
subs".  Just to name three examples, I believe JL Audio, Image
Dynamics, and Adire all manufacture their own subs rather than simply
re-badging someone else's.  I suspect the same is true for Infinity,
MB Quart, Alpine, and most of the other big brands.  While the 15"
"Boom-A-Lot" brand subs you find at flea markets for $50 are probably
a mass-produced item with the "Boom-A-Lot" logo silkscreened onto
them, I don't think this practice is very common among high-end subs.
There's simply too much competition between the high-end players, and
too much money spent on research and development, for the high-end
manufacturers to sell their subs out the back door for any yahoo to
slap his logo onto it and re-sell it.

Also, I find it hard to believe any serious manufacturer in the
subwoofer market is paying royalties to Earthquake for a
very-wide-surround design, for two reasons:

1)  Compared to the history of loudspeakers, Earthquake hasn't been
around all that long, so I doubt they hold any patent on something as
simple as using a wide surround, considering the sheer amount of prior
work done in the field before they came around.  Perhaps you could
post the patent number so we can look it up and see exactly what
Earthquake holds the patent for?

2) Having a very wide surround in a subwoofer is a poor design
decision anyway, since it reduces the available amount of cone surface
area for a given basket diameter.  This is why JL (among other
companies) has gone to using a taller, narrower surround.  If you look
at the cross-section of the surround used on their W7 subs, it's so
tall and narrow that it's almost a semi-circle or an arch.  Since the
surround is narrower, the cone area can be larger, giving the 13W7 the
same piston displacement area as a conventional 15-inch sub that uses
a wider surround.

Scott Gardner

It's true that amplifiers don't "push" their power, they only provide
their power based on what the speakers draw.  That being said, the
draw from the speaker is ONLY dependent on the speaker impedance, NOT
the physical size of the speaker itself.  If a speaker has an
impedance of 4 ohms at a particular frequency, and an amp provides
300W into that impedance, it doesn't matter whether the speaker is a
subwoofer or a tweeter - as long as the impedence is the same, the
power delivered by the amp will be the same.

 The main reasons why people don't provide as much power to their
mids and tweeters as they do to their subs are:

1)  Subwoofers are generally less efficient, because the moving parts
(coil, cone, and surround) are more massive, and require more force to
accelerate/decelerate.

2) (And this is the big reason)  Our ears are *much* less sensitive to
low frequencies than they are to higher frequencies.  140 dB at 50 hz
will tickle your belly and give you the "thump in the chest" that many
people love, but 140 dB at 8 khz will leave you writhing in pain on
the floor.   This is why even the best systems don't have a
perfectly-flat frequency response.  The response intentionally slopes
upward as the frequency gets lower, to compensate for our reduced
sensitivity to low-frequency sounds.

Scott Gardner

While ported boxes will generally play louder -at certain frequencies-
than a sealed box, there are several significant drawbacks to using
ported boxes:

The frequency response of a ported box is a lot more uneven compared
to the frequency response of the same sub in a sealed box.  If you
look at the frequency response curve of a sealed box as the frequency
decreases, you'll see that the response rolls off gradually, at about
6 dB per octave.  This means that even in the very low frequencies,
the sealed box will still be producing significant volume levels.

Now, look at the curve for a ported box as the frequency decreases.
As you approach the tuning frequency of the box, the response curve
will actually increase, giving you a nice 3-5 dB "hump" in a narrow
range of frequencies.  As you go below that frequency, however, the
frequency response falls off like a rock, usually at 12 dB per octave
or more.  This means that while a certain speaker may play 3-5 dB
louder near its tuning frequency compared to the same speaker in a
sealed box, the ported enclosure will be significantly quieter at
lower frequencies.  Some people like ported boxes because of the
"hump" near the tuning frequency, but I prefer to use sealed boxes
because the response is more even.  If I want more SPL, I just buy a
bigger amplifier - watts are cheap these days.

Also, sealed boxes are much more forgiving of errors in box volume.
You can go plus or minus 10% on the enclosure size before you really
start to notice a difference.  Since a ported box is essentially a big
"whistle", tuned to resonate at a certain frequency, the volume
measurements are a lot more critical to the speaker's performance.

Since the air volume in a sealed box (also called 'acoustic
suspension', for the following reason)  is sealed, it acts as a
"cushion" to help keep the sub from overextending, so sealed
enclosures tend to be more forgiving if you occasionally overpower the
speaker.  In a ported enclosure playing at or near its tuning
frequency, there's almost no cushioning effect, so it will be a lot
easier to "bottom out" or possibly damage your subwoofer if you
overpower it.  This is why you often hear a mechanical "clacking"
noise from a ported box when it's driven very hard near its resonant
frequency - that's the sound of the mechanicals of the subwoofer
hitting the end of their excursion travel.

In a ported box, you also have the potential for audible port noise,
or "huffing", especially if the port is connected directly into the
passenger compartment.  Since a sealed box has no ports, there's
obviously no potential for port noise.

As for "accuracy" and "tightness", those are subjective terms, but
given the smoother, flatter response curve for a sealed box, I'd argue
that a sealed box is actually more accurate, and there's a lot of
evidence that sealed boxes sound "tighter" as well.  With a
well-designed ported box, the differences can be minimized, but you're
still more at risk of ending up with thudding, "one-note" bass using a
marginally-designed ported box than with a sealed box.

I won't go into front-facing versus rear-facing subs, since that's
been beaten to death in this group.

Scott Gardner