A few quick thoughts as I take a break from breaking in my Alnico monitors and Super Zen, which were first turned on a week ago.
I don't have subs.
It's still early, but the tonal accuracy — especially in the bass clef region — of the Omegas is remarkable. The Zen is playing a part, too, I'm sure. I've been listening to an authorized release of a Grateful Dead concert I attended in early ’71 at the Capitol Theater north of NYC, a venue with a well-deserved reputation for magnificent acoustics. I had a very good seat and very clear memory of Phil Lesh's bass tone at that time, and everything in my playback chain is working together to match my memory to an astonishing degree. When I've listened to other recordings where I don't have personal memories of the performance, the identity of the bassist is immediate: Ray Brown, Charlie Haden, Charlie Mingus, etc. all sound like themselves, even when they're going for different effects by varying how and where they strike the string. I'm also happy with what I'm hearing from symphonic bass sections, baritone sax, tuba, etc. And I'm only a week in.
It's important to remember that while the fundamental of a bass note may fall within the range of a sub, that fundamental note also carries overtones that will extend much further up the frequency scale, well into the tweeter's domain in a 2-way system. Those bass overtones are an important component in the overall harmonic scheme of the music. One of the most important virtues of single-drivers is that all frequencies are coming from the same driver. As good as the Omega subs are (and they were very good when I heard them with Alnico monitors at ZLS's house), they won't quite match the primary driver.
When I acquired the Omegas, I gave my electrostatic, single-driver Acoustat 3s to my friend John, a film composer, producer, and engineer whose primary instrument is electric and acoustic bass. He first plugged in a pair of (non-Omega) subs, but quickly decided to go without them. "The bass sounded out of tune," he said. For what it's worth, I never had subs with the Acoustats either, and for a time I inflicted my bass playing on a paying public.
Still, it all comes down to personal taste and and the live music you're listening to. I'm more accustomed to hearing un-amplified acoustic bass or electric bass played through a single speaker driven by a dedicated amp. But if I spent more time in rock & blues venues today, I'd probably want subs too. I'm sure DBC's system sounds magnificent.
Rob makes a good point about DACs. I'll just say that I was anxious to learn if my little Meridian Explorer would stand up to feeding the new amp & speakers. It sounds like a champ, especially since Audirvana Plus is feeding it 24/176.4. What it's doing to old recordings from the ’30s and even the ’20s is amazing.