[garethsnaim]

Hi all. Been researching adding a sub to my 3 series. Thought I had it sorted however, I believe that being from the UK, I have a 'Base' audio system, whereby the amplification is coming from the head unit and therefore presumably there will be nothing in the boot? (Assuming the head unit is the screen part?)

On this basis is adding a sub game over?

Cheers!

[Zheez]

You can still add a sub - I did it with my previous F30 which also had base audio. It wasn't the most elegant solution but I just spliced a line level converter into the front speaker wires which then gave me the RCA outputs to run to my sub amp.

You have to use the front speakers because the rear speakers have low frequencies filtered out. I tapped into the speaker wires behind the head unit but the cleaner and easier solution would be to tap into the wires at the subs under the front seats.

It worked fine and was a clear improvement on bass without spending a lot of money or too much effort changing everything in the car but I'm sure people into their audio would criticise the bass output from line level converters. It just depends how far you want to go and how much money you want to spend as to whether or not this is the solution for you.

[Billfitz]

Originally Posted by Zheez

I'm sure people into their audio would criticise the bass output from line level converters.

Only those who are clueless, but there's a lot of that in audio.
OP, I would change swap out the 6.5 inch underseat woofers for 8 inch SWS Earthquakes, adding an amp to drive them. You need an amp with high level input, taking the signal from the speaker wire going to one of the existing woofers. For instance: https://www.amazon.com/Watts-Mosfet-...3d670b6bc&th=1