Velodyne HP/input circuit?

Hi,

I have a Velodyne SPL-1000II active subwoofer. The build-in HP circuit for the main speaker output are the question:

They cut at 80Hz/6dB oct. and I am wondering if I could improve quality on this crossing. Is it passive just with a RC or is it made together with some op-amps?

And how are the wo cannels summed for sub signal?

I would like to avoid op-amps for main speaker signals and have two options:

1. Make the cross at the pre with a quality Cap i series
2. If passive inside sub, improve components (caps)

When using build-in 80Hz, there are still signal when sub is powered off, will that indicate complete passive cross?