TL:DR: swapping out the HiVi B4N woofers with ones from a Micca MB42-C center channel resulted in (my ears/perception) improved clarity, less "shouty" or harshness, reducing ear fatigue and very very slight reduction in mid-bass as the only downside. Overall improvement imho.

Video link to see how they look/more info:

Ok, so I've had my OS's for a few years now. recently picked up a pair of Mission M70 cheap at a garage sale and absolutely fell in love with the liveliness and clarity of my OS's got put on surround duty at my PC gaming/movie station. I was actually really bummed because I thought the OS's were great, but now every time I listen to them i hear the flaws, sounds like someone singing through a tin can by comparison.

Fast forward to last week - i picked up a Micca MV42 center channel super cheap ($50 CAD amazon "renewed" discounted due to minor cosmetic damage) to try as i'm having a problem with gaming where i just cannot get surround gaming to work right without a center channel. Anyways I didnt like it - just too big for a desktop/placement issues.

I noticed the woofers were identical diameter as the ones in my OS's - even the mounting holes matched up - so out of curiosity I popped one in and did a very long and thorough comparison sound test side by side.

I can say (edit: to my ears) this is an improvement as far as clarity and separation of sounds goes. I can pick out certain instruments in songs that i would barely notice with the HiVi woofers.

What I noticed specifically:
- Much improved clarity - esp on vocals, guitar, string and wind instruments
- less shouty/harshness with certain vocals and rock/metal guitars - more enjoyable
- Slight loss of mid-bass, but not much at all…

Overall, I consider this an upgrade. I am loving the sound of my OS's again and I think the woven carbon fibre woofer looks as nice as the Hivi aluminum cone...

I'm going to finish the swap later this week and make them my mains on the desktop again for a while, then compare with the Mission M70 pair head to head - i suspect the Missions will sound a bit better still in the mids, but only by a small margin, and the m70's are relly lacking in bass. I am without a subwoofer right now but will be adding a DIY infinity 12" soon - already started that project.

I don't have measurement equipment, and the specs for the Micca woofer are not published, so this is all subjective based on my critical listening, multiple songs from a playlist i have curated for testing audio gear.