May I just ask what you did to remedy this? I'm having the exact same impression after going from Empyrean and Stellia to the Abyss.
I've only had them for about a week and their technical abilities are tremendous, they're comfortable and I get the great bass response everyone's talking about. Yet, I'm missing the chills I would get from a good vocal on the Empyreans. Emotional distant is the perfect word for how they feel at the moment. I'm using a Hugo TT2 as DAC/amp and it doesn't sound like anything is missing per se but still...
I'll take a bite. You should really consider getting the Superconductor cable then. It brings a richness and forwardness to the mids/vocals that is missing from the stock. The change in flavor reminds me a lot of the Empyrean actually. A few pages back I gave it a decent review, with comparisons to Norne Silvergarde S3 and Forza Noir Hybrid cables. Both had more fleshed out vocals than stock.
Joe Skubinski recommended burning the cable in for 75 hrs. I burned them for 85 hrs just to be sure. I am happy to report a noticeable and worthwhile change. The treble is more crisp than it was before, with more air. Even before burn-in, SC treble is still smoother compared to the stock treble.
As for the SC bass, there is more sub-bass rumble than before, which agrees with Joe's prediction of more extended bass response. As for the bass impact, I honestly can't tell if there is a change. I was really hoping the bass experience could match the visceral power of the other 3 cables but it still falls a little short. Bass detail and body with my ears in the correct position (I notice that when my ears are closer to the front of the earcup the impact is huge, but at the cost of bass timbre/detail/body) are satisfactory and well-heard, but not as well-felt.
I haven't learned any new electrophysics since my pre-med college days, but I'm wondering if the thicker alumiloy wire gauge on the SC is responsible for this reduced bass (to be fair, still far better than other headphones). Does anyone know if thicker wire gauges also reduce the perceived volume? Volume matching comparisons are a pain because my set up requires the use of XLR3 adapters for the TT2, and mini XLR3 Abyss adapters when using other 3rd party cables. Switching is laborious.
TL;DR version. For better tonality in the vocals range, try different cables. The SC achieves what I think you're looking for and does get slightly better after 75hr burn-in. The difference is slight but much appreciated. Added bonus for TT2 users, Filter 4 rolls off some treble and adds a smidge more lower mids.