Thanks @mitr . Since posting this question, I realised the magic words I needed to search for were “bass management” - and then I discovered a number of related threads.
So I realised now that the simplest way to get 3 or 4 channels out for 2.1 or 2.2 via one USB may be with a relatively inexpensive (€400) miniDSP U-DIO8 capable of 192kHz at 24 bit as reviewed by Kal. Or there’s the seeming bargain €989 Okto Dac8 Pro (which I think you’ve yet to review Kal?)
Thanks for the feedback @Jim_F. Your suggestion of using two zones is explicitly the subject of another thread. However, I’ve discovered that this approach has been dismissed in yet another thread as not being appropriate by @danny, Roon Labs’ COO .
Life in stereo at home used to be so simple, until a few things happened. My son convinced us to install a projector and screen, so we had to rearrange the room. Moving where we sat revealed some seriously bad room nodes that until then had gone unnoticed. Using multiple subs (2 is good but 4 is exceptional) with a miniDSP2x4HD running filters created using Multi Sub Optimiser sorted out the bass frequencies up to 80Hz in a way that previously I thought impossible - very flat, deep, impactful, and extraordinarily even across the listening area. Dirac running on an AVR addressed everything else extremely well, but - and it’s a big but - Dirac brings down a veil that leaves subtle complexity congested. So running Dirac Live on an Arcam AVR850 or NAD M17 isn’t the answer either - I’ve tried both. Maybe it’s the 48kHz internal processing rate on the hardware that causes this, but it could be a host of other things.
I know my Wilson Benesch Square 5s and Audionet AMP I v2 are capable of delivering much more than they do currently, because of shortcomings in what they’re being fed. I just need to sort out how to achieve room correction and bass management in the digital domain to high quality. I’ve read about Audiolense and Acourate, both of which which can generate filters that Roon can convolve. Based on the comments of others, this approach seems to offer the prospect of achieving what I’m after. The challenge that this post seeks to address is finding the optimal means of getting the digital signals (stereo left and right, and sub/subs) into the right DACs.
It’s a complex area, and there seem to be lots of options. I’m open to suggestions and comments.
Currently my Roon Core runs on a Synology NAS in another room, so I’d been thinking of buying a fanless PC (either the Roon Nucleus or building my own) to locate with my audio equipment. That would allow me to connect the DACs by USB, at the same time as upgrading the processing power of the core, without needing to buy a multichannel Roon endpoint. Does that make sense? Which would then that lead to the question of how to connect multiple DACs.