recommendation for speaker wire to soften the highs if possible

I’ve got years of experience, and in the abstract they suggest that the room may be a contributing cause, but cables are the primary cause. 

Nonoise, 

"I have about half a dozen speaker cables and every one of them sounds different. It’s just the nature of cables. A designer is going for what he/she thinks sounds best or can sound best for a variety of different systems."

True, that's why I like the cables engineers made in order to minimize such issues. 

@gunmetalzin,

You didn’t mention whether the Ryan speakers are the R610 or the S610. But at least in the case of the S610 this figure apparently depicts the frequency response of the speaker under typical in-room conditions, for rooms in which a relatively small speaker such as that would be used.

Given the modest downward tilt of that response, and given also the speaker’s 8 ohm nominal/6 ohm minimum impedance (which, everything else being equal, will tend to lessen sensitivity to speaker cable differences compared to speakers having lower impedances), and given also the room characteristics you stated in your 10-30-2018 post, my guess is that the root cause of the issue is upstream of the speaker cables. Erik_Squires and Sleepwalker65 have made good suggestions which could help to confirm that. And perhaps the experiments you indicated in that post that you intended to do have helped in that regard as well.

I don’t think you’ve mentioned what you are using to stream Tidal into the DAC. If it is a laptop computer one thing I would certainly try, if you already haven’t, is running it with its battery, and unplugging its AC adapter from the outlet. And if it is a desktop computer I would turn it off, unplug it from the AC, and try using some other source, such as the digital output of a CD player. I’m envisioning that either the computer or its AC adapter may be introducing noise that finds its way into the DAC circuitry, either directly through the connection between the computer and the DAC, or via the power wiring, or as a result of a ground loop. In turn resulting in timing jitter at the point of D/A conversion (which could certainly be consistent with harshness in the highs), and/or intermodulation or other effects on analog circuitry.

IME having an AC-powered computer connected to an audio system can often be bad news. In any event, though, as several others have indicated it would be preferable to determine the root cause of the problem, rather than band-aiding or compensating for it.

Good luck. Regards,
-- Al

Tinned, stranded copper wire in cotton sounds quite different from solid core silver plated copper wire in Teflon.  Yes, wire and cabling do change the sound of a system independent of technical reasons.  Materials matter as they influence sound.  

Granny’s Duelund cables are the bomb!