I have been using my Sennheiser 800 cable for about 3 weeks now.
Lindsay is a professional and extremely courteous via Etsy communication. He was also patient with my requests and my sometimes, inexperienced questions.
I had modded the Senns with the Super DuPont resonator and cork mod. This had all tamed the treble frequencies and that pesky 10khz spike a bit with the stock cable.
I looked up Lindsay's shop on etsy and was curious about his prices for his Litz - superior quality cables. The price was extremely reasonable and I knew copper was the way to go.
I waited patiently and then Lindsay's cable arrived. Perfectly packed and all plugs protected in bubble wrap. The cable is pleasantly pliable with just enough tension to be virtually tangle free. The braid is brilliant.
They are gorgeous. The copper is almost gold-like in its iridescence. The connectors are solid and the heat shrink is professionally applied. I opted to not go for the splitter and nothing suffers for it. But I'm sure it would look even better with! Pictures are at the bottom of this post.
More importantly the sound is lovely, smooth and yet lively. The soundstage is still there and the bass benefits from a bit of resolution and oomph but the best of it is that the treble has been tamed to reasonable and yet still airy levels.
I cannot recommend his cables enough. Reach out to him via Etsy. Ask him about his Litz line and get yourselves some custom cables without going into debt or feeling guilty for spending nearly as much as your cans.
I highly and without reservations recommend Lindsay and his shop. https://www.etsy.com/shop/ImpactAudioCables