Haven't used those exact ones but have used a lot of similar type tweaks on two different sets of speakers now. With Synergistic I have a long history of using a lot of their stuff and after years of experience it is kind of like yeah, go for it. Like recently their Purple Fuse everyone says is at least as good as QSA but costs less. So the value will be there, is pretty much a given.

Zobel network, with a twist (a notch filter). Corrects phase issues. IF you're working with woofers I found an active crossover eliminates all the funky passive XOs trying to fix the bass boo boos, passives CAN'T.

Active crossovers, direct amp to driver coupling, aided with mechanical correction is almost as good as servos. You get the bass to do anything you want lets put it that way, without having to fiddle with passive parts.. PITA passive is NEVER great in every room.

I've tried a lot of filters, notches, nothing. If you can afford an active system, you're miles ahead of the crossover crapshoot with a lot of the factory stuff. They are usually pretty cheap components. I really like it when manufactures seal their XOs. YOU know there is some real cheap crap used then.. WHY hide it? I know it makes it work better. :-)

Outside the box works even better, so we can see the cheap-a$$ parts they used in 200k speakers. Nothing is better than outside the box. Period.. The problem in this case is what is left inside the box is still messed up, add a filter? I say chuck the whole mess.. LOL

The money spent on filter would replace factory passives with TUBE driven actives. Here is a two way.

STL in Canada. They are into BIG valve tech, BIG time.. 100s of valve combinations..

Regards

SteinMusic Speaker Matches Plus works with my B&W 800D2 with a noticeable improvement.

@millercarbon Thanks for the positive feedback on Synergistic.

@oldhvymec I will look into Active C/O

@drpie Nice system, will investigate the StienMusic.

Have the feeling going to have a few options......

STL will be the last stop of my gear journey. I use to have active tube driven crossovers. They got nicked in 2015. They were set up for a three way with Strathearn Ribbons. I just acquired 8 NOS 24" drivers.

I don't even want the guy to ship them.. I'll drive the 2,000 miles in the spring and pick them up. Nervous Nellie, My hair falls out when I think of them being shipped. :-)

Regards

3rd party Zobels can work work... but the biggest expected improvement is with tube amps and speakers with big impedance rises in the mid/treble crossover regions.

Of course, you could also buy speakers which inherently lack those peaks, like from Fritz. :-)

If you want to understand how they could work, take a look at some tube amp measurements from Stereophile, and look at the curves with a "simulated speaker load."  Those ups and downs can be flattened somewhat.