Dynaudio is an OEM option. It's like an extra amp that's fitted under your seat (pax seat for us over here)
If you've got Pioneer then it's odds on you don't have Dynaudio. The speakers were upgraded too and have Dynaudio written on them

You say system works but driver side woofer's weak. I don't have the speaker pin outs for Pioneer and don't know whether someone's just jury rigged the connections behind your head unit or used a proper connector to match the car's wiring to the Pioneer.
If there's a large black connector with a lever behind the headunit then you can check your larger speaker for operation with a multimeter (you should get a good crackle when you're on the right terminals and your multimeter will indicate near to zero on the Ohms range)

Let us know how your connections are behind? Can then post chart for the connections. Pin #s are too difficult to read in the dark behind there...

 

Thanks. I am going to start with pulling the door panel to have a look at the speaker, and perhaps try a different one I have laying around.. If the speaker is OK, the next thing is to pull the head unit out to see what's up...

 

No, that's not the way round to do it. You won't get to the speaker connections that way. Standard speakers in the door are plastic riveted in so you'll have to drill out those to get to the rear of the speaker. After you've removed the door card, and all the stuff that's on the door card -- levers and switches

Start with the rear of the headunit. Fingers under the bottom of the surround (only fingers, it's very thin alley) The two bottom clips will eventually click out. Remove the airbag bulb and bulb holder from the surround without disconnecting the wires (otherwise you run the risk of getting an airbag fault needing VCDS to clear) The surround's now out of the way. There's four T10 screws holding the headunit in place, remove. You will now be able to gently slide out the headunit. And you can then see whether the connections have been made properly by the large black connector with lever on it. Or just taped together as some do

These standard Passat door speakers just don't go faulty for no reason.

Removing the door card is a pain and you'll probably break one or more of the door card clips as well coz there's a special VW tool, that comresses the shaft teeth on them. You can use a twisted coat hanger, but you run the risk of (a) cut hands, (b) breaking the clips

 

Yikes. The headunit is not OEM, it is a single DIN placed in a plastic housing that fills the opening.. I will have to see how to pop it out to check the wiring behind, no idea how this was installed and by whom.. thanks for the warning about the door speaker... We do have a company here (Crutchfield) that sells all manner of adapter connectors and plugs, etc. to allow this kind of install.. I hope that was done as opposed to a 'hack' job...