Hello.

Just wanted to drop this knowledge here so someone else can have it.
I run the IT sector of a company and we own ~60 of these headsets plantronics poly Blackwire C3220 (Now HP).

Quality is good, but the planned obsolescence is evident.

They last, on average, 2 to 3 years.

The cable is awful, if the end-user is next to the window and the sun hits the cable, after a while, the cable starts to peel off the rubber coating, exposing the wires and breaking. Also, the padding on the ears is not very good, some users are OK and others have their ears hurting after a while. It also has a poor quality material so it will start to disintegrate, so be sure to get some replacement pads.

The repairability is close to zero, it's all using a very thin copper cable. It's not zero because you can at least open it with a special screwdriver and see that it's not repairable.

Hope it helps.

Finally got stuck taking a conference call from my home office today, and I figured I ought to try out the random junk headset my employer's IT department provided for home and mobile use. Opening the package of the Plantronics Blackwire C320-M, I'm not feeling much hope. Flimsy plastic build, Grado-style donut pads, flimsy cable terminating in a standard USB jack. Plug it in and put it on and... well, at least it's comfortable. Despite no real padding besides the on-ear foam pads, the headband feels fine, and there's no real pressure on my ears. The mic adjusts easily and stays in place fine.

Needless to say, this thing worked fine for the call. No issues. Voices are clear, the mic works well; for its intended use (calls and video conferences), this thing does what it's supposed to. I wouldn't trust the build quality to survive being thrown in bags or whatnot, but if you're using it at your desk, I expect it'll hold up fine.

But who cares about intended uses??? As soon as the call wrapped, I threw on some music. Setting aside my usual home rig (6xx and JDS Atom), I ran this thing through the USB port on my docking station and fired up spotify. I'm not sure what I was expecting. But this thing sounds... surprisingly decent?! Better detail retrieval than expected, decent soundstage, oddly pleasing midrange tonality, and just enough warmth down low make for a surprisingly good listen.

My ears are by no means perfect and I don't have a means to measure this thing, so this is just a quick subjective take based off the handful of tracks I threw on. There's a clear mid-range emphasis, which makes sense given the intended use case. Guitars and male vocals sound rich and full. Treble isn't pronounced but it's there, if a bit "tizzy" for lack of a better word. Not sibilant per se, but cymbals don't sound particularly amazing. No real sub-bass, as expected for a set of uber-cheap on-ear openbacks with mock Grado pads, but there's enough warmth in the low-mids and upper bass to give the semblance of a balanced sound signature. But the star of the show is the mids, which are clearly emphasized but reasonably musical; upper mids can get a bit shouty on some tracks, but it's not shockingly out of balance the way you'd expect for a call-oriented headset. Listening to the latest Katatonia record, the subtle details sound surprisingly good - the mellotron and hand percussion that usually sit well below the mix come across as impressively rich and textured, and with a decent sense of soundstage and space, all things considered.

I spend a lot of time listening to Koss's on-ear models, so those are natural comparison points. These are clearly less bass-oriented than PortaPros, and I prefer Koss's tuning more overall, but these are a bit more comfortable than KPH30i's and significantly less congested. Highs seem more present than Portas and the KPH, but probably not compared to the KSC75; the "presence" here is probably more related to the boosted upper mids than actual highs, but the tuning works better than expected. It's nowhere near as balanced or satisfying overall, but something about the mid-forward signature reminds me of a budget Sennheiser 58x, at least when listening to well-recorded and mixed organic instrumentation (Michael Hedges' "Ragamuffin" sounds pretty incredible, tbh). Ambient textures also sound surprisingly good, with a bit of unexpected warmth (Michael Brook & Pieter Nooten's Sleeps With the Fishes sounds almost as good on these as it does on my 58x, despite the dearth of sub-bass). Listening to something more sonically dense and aggressively mixed (think early 90s death metal) leads to a flood of upper mid content that grates on the ear after a while, but it's still more balanced sounding than I might have expected.

Anyway. The takeaway here isn't that you should run out and buy these. I was just surprised at the quality of the midrange presentation, and by the fact that a junky little headset could keep me reasonably engaged for an hour when I had a 6xx right in front of me. I haven't tested many cheap headsets so maybe this is par for course, but I imagine you could do worse than this one.