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Tapping into rear speaker wires for an aftermarket amp??

16K views 14 replies 8 participants last post by  waldorf 
#1 ·
hello all, im new here :p

bought my 2007 E81 (i think lol) 118d se about 4 months ago and now im bored with the lack of bass from the standard setup :(

i have done quite a bit of sub wiring in the past but always had an aftermarket head unit to play with so it was simple... now im trying to do a sub install without riping my car apart in the process.......

obviously the battery is in the boot so thats simple. now i just need the audio inputs for the amp. ive done a bit of research and so i know i need an amp with speaker level inputs as oposed to rca inputs and an amp which senses when to turn on thus iliminating the remote signal cable thingy. ive been looking for days now and cant seem to find anything about wiring a sub off the rear parcel shelf speaker cables :S might just be me.....

my car has the standard head unit and speaker setup so no existing subs to tap into as far as im aware

so what i want to know is,
1) is it possible to tap into the rear speaker wires to power an amp and sub?
2) if so, do i need to tap into both ore will just one do?
3) and how do i get to the cables going to the speakers??

any help on the matter would be most appreciated. also if anyone has any pictures that would help alot :D

thanks in advance ;)
 
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#2 ·
hello i was in the same boat & went down this root.

Inline RCA converter

the blue plug is the speaker connection which i wired inline to draw of a feed & it all fits above the boot light.


The red arrow is the boot light where its fitted


wired up to each rear speaker for 2 strong channels split over 3 channel on my JBL 1100w amp with a JBL 1000w sub, i've just got sub speaker to add to the parcel shelf & tweeters for the back seats this is all ruynning with the standard bmw system, the only problem is i cant control the sub volume like i could with my pioneer headunit.

hope this helps
 
#3 ·
Tnks for that that's realy helpful :)

I have heard of these and am I right in thinking if I get an amp with a speaker level input it will have a little 5pin White plug which illuminates the need for this converter? Can anyone comment on that?
 
#4 ·
That's correct, most amps have a speaker level input and you may as well use them instead of adding another piece of kit line a line converter. I'd only bother to add a line conveter when the amp only had RCA inputs.
 
#6 ·
Jeers forthe help guys.... The amp I'm looking at is the Orion cobalt co5001 500w mono block amp and it will accept the 5 pin speaker level input. Am I right in thinking that the 5pins are:
Left speaker +
Left speaker -
Right speaker +
Right speaker -
Ground cable

So I can just loop the ground cable on the 5pin plug around into the main ground terminal on the other side of the amp?

And the right speaker cables can be accessed from behind the boot light, how do you get to the left speaker cables??
 
#8 ·
yamaha1634 said:
Question.... If i were to use the converter on an amp with only RCA inputs, where do I get the signal wire from?
I got mine from the 12V socket in the centre console. Ran the signal wire under back sat, under carpet and then under passenger seat where the carpet has a natural joining point. You can then feed the wire under this join and under the centre console and wire directly in here. It does mean that the amp is only on when yiur ignition is on but this generally isn't a problem (unless you're really bothered about your sub being on while your engine's off)? Another alterntive is getting an inline RCA converter with built in signal wire output. This will drive the signal whener there's a current in your speaker wire.
 
#11 ·
BY the way, if you're interested in getting fantastic bass (not just very loud when required but also very smooth deep - down to 28Hz) without having a box in the boot, the Earthquake under-seat upgrades are worth a look:

I run mine with a 350W RMS amp and it's enough for any occasion :eek2:

Many others on this forum have fitted them too and I don't think anyone has been disappointed.
 
#12 ·
Just bought all my stuff today... Amp, sub, wiring, fuses, msg, converter, switches etc etc. Will be starting to build the box this weekend, il keep you all informed on progress :D
 
#15 ·
The rear speakers of an E87 do not have the full frequency range as far as I know. So you need to tap off the signal behind the radio.
If you don't know what the positive and negative lead are: disconnect the speaker, take 1.5 volt battery and connect it to the speaker, if the speaker moves forward, the plus of the battery is connected to the plus of the speaker, otherwise it will move backwards. Remember the positive contact pin, plug back in the connector and check which wire is connected to the positive pin.
 
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