Bridge Stereo Signal at Speaker Level


Junior Member
Well, hello to all firstly,

Backstory :

I noticed there was a speaker grille in the top center part of my car's dash (2005 Volvo S80), but couldn't hear any sound from it. Figured it might of been from the wires I left after installing my new HU. (Volvo has a lot non-essential wires for there factory HU) So I popped the grille to look and see the color of the wires running to it but to my surprise there was not actually a speaker in there. After rigging it some and cutting plastic I was able to get a Kenwood 6" speaker in there.

Now the problem I ran into was how to get a mono signal from stereo signal at speaker wire level (Essentially making a false center channel). Found a nifty little chart for a method just called bridge stereo.

Source : How To - Car Stereo - How To Install A Center Channel

I haven't connected it like this yet, but I'm assuming it works. BUT what I really want to know is how does this work. Looking at the diagram I can just see the signals bouncing at each other and being extremely distorted or just not working cause you have two leads running into each other. Anyone have the knowledge to explain?


hispls Veteran
5,000+ posts
10+ year member
Central Maine
That diagram appears to be for an amp that can be run in "tri mode". I would not recommend trying to make your factory sound system do that and if you don't have 5 channel processing (and music/movies recorded in 5 channel) adding a center channel is generally a bad idea.

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