You don't use the line-in RCA's if you add a subwoofer the "typical" (?) way. You tap the speaker level off the cab speaker and feed it into high impedance speaker level input on an appropriate sub (the Polk subs are the most common). This puts high impedence in parallel with your existing cab speaker so the overall load increase on the system almost goes to zero once you do the math.

To use two at a time you wire one pin to L and one pin to R assuming your sub has stereo speaker level input. This been done and tested so many times and I've yet to see anyone over-stress their amplifier section doing it this way on everything from Sys 11 to WPC to Stern machines.

8 ohms is not high impedance. 1000+ ohms is, which is what a half decent speaker level input should be at minimum in my (limited) experience.

Do the math for an 8 ohm (cab speaker?) and a 1k+ ohm (speaker level input to sub). The increase in load is insignificant.

1/[1/8 + 1/1000] = 7.94 ohms = increase in load by ~0.8%

The speaker level input could be well above 1kOhm as well, reducing that number further.

I'm not a WPC expert at all so I won't directly recommend anything to you, but your symptom sounds strange to me if their audio section works akin to Stern's, assuming you are using speaker level inputs on the sub. You should not have to disconnect the cab speaker imo to get the sub to work, and you definitely don't on a Stern machine.

If you are tapping off the cab and running into the line level of your sub you will have problems and potentially damage your sub or amp section depending on impedance, wattages, etc...

You aren't by chance connecting your sub in series with the cab speaker in some fashion? That would undoubtedly cause your issue I believe...

FYI I'm not an expert. I've just hooked subs to pinball machines, and dabble with audio as a hobby. In my experience, speaker level inputs are as close to bulletproof as you can get - there are very few ways to hook them up to "average joe" equipment and actually damage anything.

Their weakness (imo) is in volume/crossover functionality over multiple source materials. Bassy music might sound great at one setting, but then your movies sound like crap, or vice versa, and you have no control over the sub signal at the speaker level input - only volume of the whole signal.

For pinball this is largely irrelevant but this is why this post rings true:

The settings for a 'good sounding' sub on different eras and styles of machines change, and since we're using speaker level signals, you cant boost or cut the bass itself on the fly, only the overall volume. Hence, it works great to group machines together that 'sound similar' for any sub running multiple signals.

Oh no worries. I didn't see you being combative at all. If you are using speaker level inputs on your sub in parallel with your cab speaker I don't know of a way your cab speaker (or it's signal) would be affected. The other thing to try is to invert the phase on the sub if you have that capability. Sound does strange/cool things if you are getting phase cancellation - inverting the phase of the sub might help clear up some muddiness you are perceiving to come from the cab.

What I would recommend is taking a picture and/or drawing a quick diagram of what you have wired to where. If there's anything wrong with the setup, we/I can better help once it's confirmed everything is wired properly.

Ok so after getting back on this tonight, I have pulled the specs on your sub and this SA-W2500 subwoofer of discussion does appear to have stereo speaker level inputs so you will not need something more complex such as these adapters/boards to drive multiple machines thru one sub. If you hook two games to one mono input, you will indeed alter the impedance of the speaker circuit but it has absolutely nothing to do with the sub itself, its the two machines being tied together that is the problem - just keep the two machines on two separate inputs to avoid this.

On a Polk PSW10 you can run two machines into a single sub as it has stereo speaker level input. The sub does all the rest of the work internally; You don't damage the machine, you don't damage the sub. This is what you've read about on the forums but it is restricted to subs like the PSW10 who can take in multiple and separate speaker level signals

_{Post edited by Purpledrilmonkey: Correct specs show single, but stereo input}

Really? I did not think so... *runs to check*

Edit: indeed it does. Cool.

It's not unsolvable. Your speaker level inputs already do what this device does - Line output converters are for devices that don't have speaker level input, which your sub does according to the specs I read.

My final super short easy-as-pie way to add a sub:

Take a Polk PSW10 or equivalent, run one pair of the speaker level inputs in parallel with the cab speaker, aaaaand done. Everything else in this thread is overcomplication in regards to getting an external powered sub hooked to a game.

I apologize if this seems curt but between the expert advice and the marketing efforts in this thread, I've had my fill trying to convey how easy and cheap this actually is.

I'm bowing out at this point. Best of luck!

You got me back.

Don't disconnect anything. Add the sub in parallel to the cab speaker with speaker level inputs.

sub2.png

That's it. No more is required.

Now I'm out