If you plan on using both L and R for 3 x 2 pinballs, total of 6, then I suggest you get a device that has independent grounds. If you don't, and plug 2 pinballs at the same time in an input's L and R , then you will be joining the speaker wire of 2 pinballs together and if you didn't wire properly you could be joining one pinball's ground plane to the others output audio signal. Now just like this it might not do anything special, but it might create a ground loop, if the grounds are tied together through the earth ground.. It's just not a great idea. You would still need to make sure that the ground isn't shared at all inside that selector switch.

While searching for your device, I thought I had found the right one, but they differ. Anyways this one seems suitable :

https://solupeak.com/product/solupeak-u31-rca-audio-source-splitter-3-in-1-out-stereo-signal-cable-selector-hifi-rca-passive-switcher-with-signal-lossless-compact-connector-distributor-box/

This one is more expensive, but seems better quality too. One important design feature of this one is that : >>RCA terminal and signal switch are directly soldered on circuit PCB board, no wire is used, *** the left and right channel grounds are separated ***, the aluminum shell for shield, and audio signal lossless

Meaning every jack is totally independant from the others, so it actually gives you a possibility of having 6 pinballs connected to the same subwoofer, if that subwoofer has 2 speaker level inputs.

I am not an audio expert at all (I am an electronics tech for the past 20 years though), so I might be wrong and maybe there aren't any major risks of mixing speaker wires from 2 different pinballs together (it SHOULD be fine if you are correctly using the ground from both machines), but I would really put extra care on that. Don't cheap out on this aspect if it can potentially damage your pins or sub..

Pinnovators is the only way to go. 4 subs one 1 connection

+1 for Pinnovators.
Good product

I'm curious to which device from Pinnovators is suggested here ? I looked at their products and nothing seems fitting without having to buy multiple things. If it's the PINsmx, then it can't be used alone and requires more kits in each pinball?

Not sure which sub the OP has , but if he has a typical PSW10 , then he can already plug 4 pinballs at one time without needing a switch , because it has 2 pairs of independent speaker level inputs , in which case if he uses the speaker level, he doesn't need anything to convert it to line level like the PINsmx does.

just buy one sub for every two machines and connect one to the left input and one to the right input. for what you pay to buy the your first sub and the necessary components from pinnovators you can buy two additional subs and connect to 6 games. Or you can cobble this stuff together and hook 4 games up to one centrally located sub. The "pinball" speaker mod/upgrade market is hilarious.

Very interesting topic here, can someone explain to me that in some situations why i heard buzzing sound from the pinball that is not open. When i plug 2 different pins to 1 subwoofer? Ground issues?

Pinnovators all the way, easy and works.

where are you getting a signal level output rca jack out of the pin? do they have those now? I use polk psw10's also. I tap onto the cabinet speaker with speaker wire and hook into the speaker wire inputs on the polks. i never play two pins at a time but you could . it will just be a mixture of lows from both. with this switch you are looking at you would only be able to get sub woofer action from one at a time.

the speaker wire on the cabinet speaker is an already amplified signal. typically rca jacks take in an unamplified signal from the sub out on an amplifier. I wouldn't monkey around with that. Just buy two subs and use the speaker terminals. then you can hook up 4 pins and never have to touch anything. I have 9 subs in my gameroom. two for the audio system and 7 for 15 pins (one without a sub)

again you don't need the gadget...and no..an RCA jack is not simply a way to connect things. There is line level, there is speaker level. That is why there are speaker terminals and RCA terminals. But do us a favor. Hook it up the way you are suggesting and make sure you film it and post it here.

using one of the pinnovaters rca output boards( 35$ i think) you can have 3 pins on one polk psw10 : rca (pinnovators)x 1, speaker level x 1, speaker level x1 .

i don' t recall the polk having 2 rca inputs but if it does can go to 4 pins but for the 2 pinnovator boards needed you can just about just but another polk

speaker out of pin is speaker wire. speaker in on sub is speaker wire. If you are convererting on both ends n]back to speaker wire it will work like you want it.