No doubt the Spatial Black Hole has its benefits, and I know it can mitigate acoustic anomalies in very troublesome rooms, which it sounds like you, Spirit, have had to cope with. That was a good suggestion Sean offered.
But before the wider audience begins to think this sort of thing is necessary -- yet another box -- two things are worth keeping in mind. First, in decades of listening to both live and recorded music, I've yet to hear any of it in an acoustically perfect room. And when I've heard a "perfect room" like an anechoic chamber, treated-to-the-hilt listening room, or an engineered recording studio, it didn't sound much like music the way it's actually experienced, though the sound might have been beguiling for reasons other than realism. On the other hand I've heard two rooms that were perfectly convincing for listening to music, and neither were free of anomalies, including audible nodes and standing waves.
The two best "rooms" I've ever heard were 1/ Symphony Hall in Boston. I had a share of season tickets for 10 years when I lived there. It ain't perfect, but it's exceedingly natural, involving and satisfying to hear music performed there. The second "musically perfect" room I've heard was a family room on the first floor of a large Victorian house on the shores of Spy Pond in Arlington, Massachusetts. It wasn't a house I lived in. It happened to be dimensioned to nearly the same proportions as Symphony Hall. Otherwise it was just an untreated family room with normal furnishings, and a combination of large glass windows on two walls, a large fireplace on one long wall, and a shortwall of in-build bookshelves and cabinetry. The thing about that room was "any* combination of gear sounded not merely good but sensational in it. A receiver with a pair of $400 speakers sounded like $30,000 worth of gear, regardless of audible nodes. A friend owned the house and we made a project out of trying to make the room sound bad by installing the most objectionable hifi gear would could find. No avail. Throw it your worst -- that room made everything sound golden.
If you have a dedicated listening room and you want to hone it, have at it. Yup, the room is the big number in the equation of hi-fi. The Black Hole is a one-trick pony tackling a sliver of the problem. But then go out to listen to live music, and think about what you hear, how hearing it in compromised space isn't eliminating your enjoyment, and then go back and question whether your hifi optimization might be creating a more synthetic sound than you intended. Maybe, maybe not.
Agreed, it's absolutely true that sorting out the lowest octave's affects in your room has disproportionate benefits, and the Black Hole may be just the ticket if you have space for it or otherwise are willing to live with its presence. But if you don't have space or aren't willing to accommodate it for whatever reason, and you upgrade to Def4, you will find that the newer speaker excites the room much less, more evenly loads the room with its bass output, and generally reduces unfavorable room/speaker interaction. My moderate bass piling at high SPLs with Def2 is tamed and virtually eliminated with Def4.
The sub-bass user controls are not so simple as Def2's single level control but not so bewilderingly interactive as to cause endless twiddling. The tunability is logical and manageable, IMO. The sub driver is pretty stiff when new, so Sean gave me notice it will take some time to play in. Whereas Def2's level control offered equal gain boost and cut, with most people on setup starting with the sub level control at its midpoint -- 12 o'clock -- and then backing off a bit to perhaps 11 o'clock or boosting a bit to perhaps 1 o'clock, the expectation with Def4 is that cut is the more likely scenario, so in most rooms taking in brand new Def4s, you'll start out with the level control at 9 or 10 and back it off as the driver plays in and becomes more efficient. So I'm still at that beginning stage for level and it's spot-on. The low pass filter hinge frequency is set at 45Hz, the PEQ at 31Hz, and phase is set at 0 shift. I have no complaints but I expect to tweak these settings as the 12" driver plays in and limbers up.
Despite Def4's truly full range, I have the fewest resonance anomalies of any speaker I've heard in the room, and that includes well above the bass range too. So whatever problems you might have now with Def2 are going to be mitigated by Def4, *possibly* to the point of irrelevance.
Last, I dug further in the cabinet differences between Def2 and Def4. The front baffle is immensely stronger on Def4 than Def2, both because the further-apart spacing of the FRDs leaves more material in place at the juncture of three drivers, and (more important) the large compression tweeter and its lens form a stressed, compressing, rigid member that seriously boosts the rigidity of the front baffle at what would normally be its weakest area in an FRD-T-FRD arrangement. This is a major factor in further reducing front baffle talk from the levels reached in Def2 compared to Def1.5. Then, what you can't see is that to further drain the FRD's frame-radiated energy away from the baffle into the interior of the superstructure, each FRD's isolation chamber has an interior front-to-rear taper formed by interior side plates that are cleated into the front/side panels' mitre join, and angled inward by 15 degrees, then fastened into the rear panel. This nearly eliminates side panel talk highly evident in Def1.5 and much attenuated in Def2, plus drains the FRD energy into the rest of the cabinet where it is then steeply damped by the rigid aluminum plinth that bears the rest of the mass of the speaker.
Phil
