I have recently gotten rid of my home phone service and now have empty lines going throughout my house. Now in my master bedroom, I have a Tv which has lackluster speakers on it. However, I have in-ceiling speakers which I've hooked up to a Sonos system. This system can automatically switch between tv audio and music streams. Unfortunately, the amp is in the basement in the exact same spot as all of the telephone lines terminate. Is there a way to run the TV-speaker's left and right audio signals through an rj11 port to my basement audio setup?
I wouldn't even consider it. Any length of wire that small (24 gauge, I think) has way too much resistance for any type of speaker connection, period. I'd recommend 14, but you may get away with 16, depending on the length of run. Yes, it would be convenient, but not feasible or recommended.
If you want to get a line-level signal to the basement for amplification, you can always get a quality shielded cable. the L and R signals are red and white, with the neg as the shield. Or get a shielded 4 conductor cable. Using one cable like this may introduce minor crosstalk between channels (EMI), but I doubt you'd notice it. Terminate both ends of the cable run with the appropriate RCA connectors, or get RCA cables with the plugs already installed and splice them onto the cable ends. That way, you won't have to solder the individual connectors.
but there’s a twist! This telephone wire is actually a cat 5e cable with Only four wires used as telephone and the other 4 there as dormant wires. I know this because I’ve transformed many of the cables running throughout my house with some wire strippers and a crimping tool. However this also included changing out the face plate and Other annoying things. Is there a way I can avoid going through all of that hassle?
So you're thinking of combining 2 wires for less resistance? You'd still end up with approximately 21 gauge, which is still too small for speaker wire of any length. You'll still have significant loss from the wire's resistance - if speaker level. If it's a line-level signal that will be amplified, it may work fine. BUT (always a but!), if it's unshielded, you run the risk of picking up induced magnetic field interference.
Yes my idea was to send the audio over the line in this pattern, This way I can use the preexisting telephone port already put on the way all nice:
Pin 1 - Shield, right channel (white/orange wire in T568B standard)
Pin 2 - Hot, right channel (orange wire)
pin 3 - Shield, left channel (white/green wire)
pin 4 - Hot, left channel (green wire)
Would this work or would you recommend I do the alterations to the wall jack and make it into an ethernet jack and just use a premade adapter along the lines of: https://www.amazon.com/gp/product/B01IXYSE2A/ref=ask_ql_qh_dp_hza
So you're using line-level signals. Yes that would work great. As far as plate mods, that's up to you, your imagination and not least, your personal taste. I've done custom plates by drilling for connectors, but there's lots out there. You can also do what you mentioned above, tuck the adapters behind the plate and just have the two RCA connectors exposed. There are many ways to get this done. I've done this: https://www.parts-express.com/parts-express-gold-rca-jack-solder-type-w-nut-pair-hex-type--091-1204
I drilled out a plate with phone connector and added them.