I think you could get away with a variable resistor (aka a potentiometer, often called a volume
knob) attached to the louder one.

I had these little ones you snap into the speaker wire but I can’t find where to get them now. I’ll try a better search after I have my coffee.

I have the same issue and have not yet tried it, but the plan is to try a few potentiometers from Amazon. https://www.amazon.com/Potentiometers/b In theory you would put one in line on the louder of the two pins and adjust it until the volume sounded right. I tried to steal one from a cheap set of headphones but the wires were way too small. I threw something like this in line into a High Speed that was too loud and it worked perfectly. https://www.amazon.com/Potentiometers/b . I did the same thing on a Goldentee to add external sound. The only issue is I don't know off the top of my head what size to get.

This guide might be helpful as well.

https://soundcertified.com/how-to-reduce-tweeter-volume/

It says it's for tweeters but same principles would apply to a subwoofer signal.

No brainer. Pinnovators taps and mixer.

https://pinnovators.myshopify.com/collections/subwoofer-kits/products/pinsmx-passive-subwoofer-mixer

Omg. So embarrassed. I must have been brain dead. Re read your original post…. Love the ingenuity on solving for speaker level conversion. My lazy ass would spend $35 for this to convert speaker to RCA and another $10 to $25 for a cheapish line level mixer from sweetwater or Amazon etc and be done. Links below. Should be perfect but same as yours (this one is a bit more flexible- single point for both pin volume controls)

https://www.crutchfield.com/S-W4MNwGfugmq/p_210MPSHL/Morel-MPS-HL.html?XVINQ=GLX&awkw=425315964428&awat=pla&awnw=g&awcr=343141751718&awdv=m&awug=9032054&gclid=Cj0KCQiA3fiPBhCCARIsAFQ8QzUxYO-3qBC4ApkE3XW4U9lV1GSbC8h5w8lZtMtMgqTF2uPyoibGnMcaAoONEALw_wcB

https://www.sweetwater.com/store/detail/MX400--behringer-micromix-mx400-line-mixer?mrkgadid=3250494485&mrkgcl=28&mrkgen=gpla&mrkgbflag=1&mrkgcat=brand&acctid=21700000001645388&dskeywordid=92700046937728380&lid=92700046937728380&ds_s_kwgid=58700005283819385&ds_s_inventory_feed_id=97700000007215323&dsproductgroupid=377818384057&product_id=MX400&prodctry=US&prodlang=en&channel=online&storeid=&device=m&network=g&matchtype=&adpos=largenumber&locationid=9032054&creative=228658011809&targetid=aud-994727058445:pla-377818384057&campaignid=741659211&awsearchcpc=1&gclid=Cj0KCQiA3fiPBhCCARIsAFQ8QzWaAjXVqlC7NA7G7JXvZeJrMl9yS7T4xS4LUReqkLIR42ESP8cWXAAaAvInEALw_wcB&gclsrc=aw.ds

Electrical engineer here...

Old thread, but I should probably chime in here. A better way is to convert to a low-level using an adapter, and use the low-level input to the woofer. By using a low-level adapter, it presents a a somewhat high impedance to the pin's audio amplifier (i.e. you're not connecting another woofer in parallel). The audio adapter is used primarily by car audio guys when they need to connect an amplifier/woofers.

When you used the mixer in your original post, you likely overloaded the mixer.

The adapter below attaches to the pin's woofer, then it outputs a level appropriate for a mixer or the line connector on an active sub. It also acts as a 'BALUN' (important for some pin's amplifiers, like a SPIKE) and breaks any ground loops.

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On a related question, I have a racing arcade that has 5 speakers. Two above the monitor, 2 in the headrest and one woofer under the seat. The woofer under the seat is supposed to give a tactile feel, so when you go over bumps and stuff it vibrates. The issue is the game is too loud for my house I'd I set the level to feel the bass in the seat. To my understanding, just adding potentiometers to the other 4 speakers to reduce their levels so I can feel the bass but not go deaf from the music would put excess load on the audio board because of the increased resistance, correct? So what would I use to allow the seat level to be louder? It's all speaker wire going to each speaker, I don't have low level line outs to work with. Just a dummy amp where one volume control built in the software controls all the speakers.

You could use what's called a 'L-Pad', that will keep a constant impedance to the amp, and they are usually rated for higher power.

Here's a random google search for an L-Pad:

https://www.simplyspeakers.com/speaker-crossover-l-pad-a-542.html

Awesome, thanks,! So I'd need 4 L-pads, correct. 4 to the speakers I want to lower the volume to and the seat speaker (which I want to be louder) I would just leave that as is running directly from the sound board/amp)?

Yep! One L-Pad for each speaker (in-between the amp and speaker) and seat speaker remains the same. If the speakers are all wired together or maybe in two pairs (excluding the woofer), you can likely get away with fewer L-Pads. In other words, if the amp has two outputs (one for the woofer, one for all the other speakers)...then you'd just need one L-Pad for the surround speakers.

I'm sort of surprised there's not a menu setting somewhere for the speaker levels? Or is there just one setting for all the speakers?

Edit: Just saw your comment about the volume control.

Sort of sounds like you are fine since you have some sort of adapter in the pins. I actually have 6 pins (thru the adapters) going into a cheap 6 channel mixer, then to two active subs. Makes it easy to adjust the pins individually via the mixer. And I didn't need to buy a bunch of individual subs.

You want the center tap and one of the outer legs. The two outer legs are across the entire resistive element, the center tap is what moves with the knob adjustment to vary the output on said tap.

You can pick either outer leg, but one leg will give you an inverted output (twist CCW to louden rather than CW)

It is worth noting that audio pots are logarithmic rather than linear taper, so make sure you get an audio pot because it'll be hard to adjust volume with a linear pot

I mentioned the L-pad comment earlier. Using an L-pad will keep the impedance presented to the amp constant.