I have a 2004 BMW 330Ci. Here is a list of what I have:

Eclipse AVN-5435

Audiocontrol Overdrive, ESP-2, DQX, and DDC

US Amps USA 200x - tweeters (50x2)

US Amps USA-400x - midrange (100x2)

US Amps USA-2000x - sub (2000x1)

OZ Audio CS-180 (old school superman logo)

1 Fi Audio Q12 D2 in a 2.0 cu ft box tuned to 33 hz with 24 in of port area (small, I know).

I just purchased an 06 RE XXX 12 to replace my 05 XXX 12. Then I heard about Fi so I bought a Q12 just to try it out.

The customer service was excellent and the sub was rushed to me in time for Heatwave in San Antonio (USACI). I got the box which was similar to RE's packaging. The box was ravaged but the sub was okay. Not sure if I can really blame Fi for this.

I installed the Q12 into a 1.0 cu ft sealed box just to check it out. I was so shocked at how light the sub was. ~27 lbs was the shipping weight I think. Much lighter than both of the XXXs which is a good thing. Connected it to my US Amps USA-2000x with the coils wired in series so the rated output was 2000 watts, 200% of the rated output. WOW! This thing got amazingly loud and very accurate. I use "Operation Spirit" by Live and the USACI focal disc to test SQ. The low end is controlled and quick, fast bass lines don't drag and are very distinct. This sub also has great output in across the 3 lowest octaves, a weakness of the 05 XXX 12. Played some Red Hot Chili Peppers and Bass Mekanik. Output continues to be astonishing. The sub has less than 45 minutes of play time and is pretty stiff.

So I dropped the Q12 into a 2.0 cu ft box tuned to 33 hz with a slot port (24 sq in). Got some port noise but I have limited space and the trunk masks the noise so its not an issue from the driver's seat. No significant loss in SQ in the ported box. Bass notes are still tight, quick, and distinct. Output...even more astonishing. Seemed to be louder than the XXX across the board. This also kicked the crap out of my 3 10" IDQs in SPL and SQ.

With the 2000 watts, I did get a burning smell after 1.5 hours with 2000 watts. I was going pretty hard on the Q and it took it. My guess is that the Q can handle 1500 watts and maybe up to 1700/1800 watts with a responsible adult. Only at the highest volume level did I notice a loss in linearity. But no nasty suspension or banging noises.

At this point I'm sold. Next day, both of my 05 XXX 12s are for sale and the 06 XXX 12 is being stored in my closet for home stereo duty in the future.

I went to the comp. Sub is still STIFF! REALLY STIFF! Along with a 1st place in SQ, I scored a 136.X (forgot the exact number). Not a great number but keep this in mind:

I forgot to put my back seat down

My car is a HORRIBLE SPL car

I didn't have time/forgot to setup my EQ for SPL testing

With that, 136 is a damned good score. I scored a 137.8 with the 05 RE XXX 12 in a well tuned setup with the back seat down. I have no doubt that the Fi Q can top that.

I was addicted to this sub for the next 30 days and then I deployed to Iraq. I got a noticeable increase in SPL and SQ as the suspension loosened up. I don't think that I ever really broke the sub in so I'm very excited to get back to the US.

This sub is similar to the XXXs without the weaknesses of weight and lack of upper bass output. For the price? Its a no brainer.

I tell people that this is the BEST deal in car audio. If anyone knows of a better one, please tell me.

Some more info....

To be honest, I was kind of weary about getting the Q and probably had the same apprehensions that all of you have.

Here is another comparison. I have had a couple of opportunities to listen to an IDMax and W7 in both manufacturer spec sealed and ported enclosures. I can say that the Q outperformed them box in either alignment as far as SQ and SPL. The big 12" sub test confirmed this as far as the W7. The Q can not be touched as far as value.

If you are on the fence about this sub, there really is no good reason that I can think of. The only question I can't answer is what advantage does the Q have over the SSD.