[purity]

Hi everybody,
My car have the Hifi System with Professional Radio,so my system should have the 8in sub under the seat.
The stock power amp is rated at 40watt (2ohms)x2.
I was thinking,instead of adding sub in the trunk,how about,if I just use a better Power Amp to feed those two stock 8in sub under the seat.

I was thinking of only using Soundtream Class A 6.0 which rated at 2x50watt (but at 4ohms),so at 2 ohms they should pump about 2x100 watts.I will feed their input from the sub high level output of stock factory amp and use hi/lo converter.

By the way,does anybody know,if the factory amp sub high level output already have some kind of active croosover (so they only pump out low freq to sub) or still full range signal?Because if it is still full range then I need to add active xover so the signal that goes to the sub only pure low level signal.

Does anybody have ever done similar things before?

Thank you

[backtofront001]

The subs underneath the front seats are shit. U are better off using them as midbass drivers than subwoofers. If u want real lows get a subwoofer man. U'll enjoy it

[purity]

Of course they are not really optimize for subwoofer,but if I want to use a sub,I need to get quite big size because the trunk is sealed very well,so small size woofer ain't going to make it.Mine do not have the rear set ski holes.

And it going to take lots of trunk space and weight a lot in the rear.While my car already lowered.So I want to avoid using sub at the rear.

[drcain]

My brother's previous gen 530i didn't have the fold down seats (and therefore probably no ski pass-thru either), but they installed a 10" or 12" subwoofer there. He just needs to keep the rear armrest down (so as to not cover up the sub), and they installed a grill with felt there to cover up the speaker. It was an open air design sub so they didn't need to take up extra space in the trunk by making an enclosure for it as well. We were a little skeptical as to how it would really sound (being an open air sub), but it seemed like his best option, so went with it. And WOW, it sounds great and really worked for him!

I don't have a 330i yet to know if you don't have the ski pass-through whether they can still create the pass through there, but they did it on my brother's 530i somehow. If I didn't have fold down seats, that'd be my #1 choice too now. Before you 'write off' that pass thru as a possibility, you may want to double check what a professional install shop might be able to do there?

[backtofront001]

Space is everyone's concern and it is a good concern since you dont want a darned sub taking up all the space. I have a 325i and in my trunk above the stock ampifier (on the bottom left of the trunk) there is space for a 1 cu ft enclosure. That would not take up any space at all. Look at bottom left of image:



and about sound getting through, if you get a sub capable of handling around 300 RMS, you will get very good SQ (sound quality) and very good sub response. Trust me you will feel it. I see u are not from the States, so I dont know if u can order one of these but here is the website:

http://ascendantaudio.com/

Check out the 12" AA Assasin -- the sub is cheap and it will take power and give you amazing results without taking up a lot of space

[purity]

Hi backtofront001,
your car color is the same as mine.But I donot have those
ski access.(my country is tropical )

But on the bottom left of the trunk,my car has a bump with CD Tray on top and under it extra space for Factory CD Changer,with a small door to access the CD Changer catridge.

It is a different interior finish then yours.So the space there is 30%smaller.But I get your point.
Still I really like to hear first from what people experience about hot rooding the front sub with higher power amp.
Beside it is already 8in speaker under the seat.and there are two of them in very close range to seating position.
But thank you for your advice backtofront001,Appreciate it