Tweaks That plug in to speakers and ? Why they work

Not totally true Erik, we used a spl meter to match output
you are correct in untouched the spl is a 1-2 db difference

Can you please point out what I posted that you are refuting with this sentence? Because it seems like all you are doing is confirming exactly what I mentioned.  The question in the OP was how they work, not what they do. :)

@artemus_5 Okay. Real class.
You are severely deficient in  grace, dignity, and intellect.
Fact is you have zero humility and you are still poor. (figure that out).
We really need that block or mute button.
You have polluted this post enough with your indignant rant.

Oh geez, I'm financially challenged. Back to the OP, please!

The filter can only take away, it can ADD nothing, that’s why it’s a filter.

Impedance matching is going to cause the onboard XO to act differently, or correctly via the way it was built and tested, either more so or less so.

I can see why quality parts don’t sound WORSE, I just don’t get how they sound better?

There must a funky factory XO, that a (shot in the dark) filter makes everything sound better.

I’d pay a little more attention to what Erik is saying OP.

HF roll off will sound better if the room isn’t treated. Mid or BASS, it depends on what the filter does. It may, and most likely does, make the ramps a LOT steeper, so they sound sharper.

Dips are going to stay dips, but peaks, steeper roll offs and a lower frequency roll off is what that filter CAN do.. It can’t add a thing..

Cheap parts in the path.. vs quality parts in the path vs NO other parts in the path. I’ll go with room treatment, tone control and NO extra parts in the path. :-)

Time to feed the Chickens...

Regards