Car audio - wiring up a 5 channel amp to just 3 speakers

andybird123 · 7 Feb 2019 at 17:41

Hi guys,
so wasn't sure whether to post this in motors or here but here goes.

I've got a van that we are converting to a camper and I'm using the excuse of having everything stripped down to updgrade the audio slightly, I've got a 5 channel amp (normally 4 @ 45w + 1 sub at 320w), but the van only has space for one pair of components, so I bought a pair of JL C3's rated for 75w continuous.

The amp is bridgeable, but the default way its set up is that you can bridge the front and rear giving you up to 120w rms, but you end up with only a simgle "front" and single "rear" speaker... so that got me thinking, if I connect up front left and rear left to front left in and front right in. The front is then only receiving "left" channels and the "rear" would be both right outs from the headunit, so bridged "front" and "rear" would actually be "left" and "right". Or even just use front left as front left and front right as rear right and don't connect the rear outs at all.

Can anyone see a problem with this?

Kei · 8 Feb 2019 at 11:38

What is the amp and how many inputs does it have?

From my experience when bridging amplifiers, you only use one input for each pair. I.e use left from the front input pair and left from rear input pair or Ch-1 and Ch-3. Usually Ch-1 is your left input and Ch-3 is your right input (even if labelled as left) Some amps don't have a 5th input and derive the signal from a combination of inputs, usually selectable via a switch.

andybird123 · 8 Feb 2019 at 15:42

Its a JBL club 4505 - it has a pair of RCA's for each of the sub, front and rear going in(which is the same as my head unit has available). Outputs; The Sub has a single pair of +/- and the front and rear have a total of 2 +/- each (which you can bridge across to use the left most + and right most -)

As you say, I think I will try a single pair of RCA's from the headunit Front outputs going one each to the "front" and "rear" inputs, where front becomes Left and rear becomes Right in effect.

There's no ability to select which inputs drive what outputs, but there is a completely separate subwoofer channel with its own ins and outs.

Kei · 8 Feb 2019 at 20:13

Based on the manual/quick start guide, the positive side of the bridge is always the left channel, meaning it should be the left (white) input used. (though they do show phono Y splitters when using a mono sub input) In effect would mean what's labelled "front" on the amp would become just front left and what's labelled "rear" would become front right and you would leave the headunit rear output disconnected.

andybird123 · 9 Feb 2019 at 09:39

Kei said:
Based on the manual/quick start guide, the positive side of the bridge is always the left channel, meaning it should be the left (white) input used. (though they do show phono Y splitters when using a mono sub input) In effect would mean what's labelled "front" on the amp would become just front left and what's labelled "rear" would become front right and you would leave the headunit rear output disconnected.

Yeah thats what I was thinking. I'll try a single pair to start with and see how that shakes out.