A:AnswerI don't know for sure, but I would have to guess no. Won't hurt to buy two kits, carefully remove packaging on one. Test, and if it fails you can return for a refund. Just be sure not to damage any boxes and tape it back up neatly.
A:Answerhttp://www.lg.com/us/home-audio/lg-SPJ4-S-wireless-surround-kit
It only lists compatibility with two models: "Compatible with SJ4Y and SJ5Y Sound Bar Models"
I would err on the side of caution and say no.
A:AnswerThe LG - 120W Wireless Surround Sound Speaker Kit - works with select LG soundbars - Black, Model # SPJ4-S is only compatible with SJ4Y and SJ5Y Sound Bar Models. ^CP
A:AnswerHi DMBjr. The LG - 120W Wireless Surround Sound Speaker Kit - works with select LG soundbars - Black, Model # SPJ4-S is compatible with the SJ4Y and SJ5Y LG Soundbar models. The product information page for the SPJ4-S on the company site, https://www.lg.com/us/home-audio/lg-SPJ4-S-wireless-surround-kit lists these compatible models under its 'Key Features'...^IFV
A:AnswerRegrettably, the LG Full HD 1080p LED TV - 49" Class (48.5" Diag), Model # 49LJ510M is an entry level TV that is specifically designed for people not looking to add additional speakers to their TV or to augment the TV's sound so it does not have an Optical Digital Audio Output or any other audio outputs. ^CP
A:AnswerThe SPJ4-S will not work with the SJ9 no matter how many firmware updates you do. If you want rear speakers for it you'll have to track down one of LG's music flow speaker but they discontinued those last year, so hard to find