Car Audio Question - additional subwoofers

[+Nik Louch Subscriber²]

I have just taken ownership of a new Ford Focus (ST Estate). It’s lovely and has the upgraded B&O speaker system which includes a small sub in the spare wheel arch.  It has a nice little rumble but not a lot.

If I buy couple of subs in an enclosure, and a suitably specced amplifier - can I easily add it?

My thinking is that I take the signal from the existing sub (keeping it wired in) into the new amp, then take power from the rear - should that work?

Let me be clear, my desire is to ADD to the existing system rather than replacing the sub in the trunk.  
 

Thanks

[Jim K Global Moderator]

Not familiar with the Focus.  Have installed amps/subs in Ford Mavericks (mine and my friends).  His has the B&O ... but not a Focus...not the UK.  Mine is the cheap one.

I would think it would be a pain to tap the amp (you would tap the signal before it reached the factory amp...not after).  I contemplated trying to tap the factory amp on my friends Maverick...but noped.

Personally I would see if they make a wiring harness (example) to where you can run the Front R/L wires to a LOC (example).  From the LOC your would run your R/L to the aftermarket amp.  Your aftermarket amp will need to be wired directly to the 12v battery (with a inline fuse).  A ground wire (same gauge) to the chassis.  Remote wire would either be audio detect or tap a fuse for 12v detect.

Also...not sure if it's the same way the Focus...but these Mavericks wake to do random BS (like check for updates).  If your LOC is set to switch on by audio detect (speaker signal) ... and it's like the Maverick...your amp/sub will power on.  I ended up finding a fuse to tap which only switched on when you turned the key (or pushed the start button in his more fancy Maverick).

I would check some Focus forums.  I didn't even know they still made them...ha.

 

[binaryzero]

https://youtu.be/JPxkYgW-axM

[+Nik Louch Subscriber²]

On 16/07/2025 at 00:31, Jim K said:

I didn't even know they still made them

This is the final generation.  I know it's just a mid-range car, but my last one gave me 11 years of worry free motoring for a purchase-sale cost of £6000.  I said for years that if money weren't a thing, I'd buy the same again.  I got to the point where money wasn't a thing, and did what I said I would lol

On 16/07/2025 at 00:31, Jim K said:

I would think it would be a pain to tap the amp

Ah yes, what runs to the sub would be an already amplified signal, I hadn't considered that.  Let me look into what you said