Regarding the questions raised by Spiritofmusic:
The downfiring sub driver has several advantages, in no particular order: In Def4, the driver is bolted to a 1.5" thick machined aluminum plinth, plus it's a cast-basket 12" driver. Mounting the sub driver to an equally rigid rear panel would require a much larger slab of aluminum or alternate material to achieve the same management of the driver's motion energy on a more expansive panel. Additionally, by mounting the driver in the plinth, the opposite wall is small and stiff rather than tall and large, so cabinet resonance is more easily controlled. The cone motion can't rock the speaker cabinet, either. Then, consider that the soundwave is projected toward the floor, which is generally a stiffer, less resonant surface than is a wall behind the speaker, at least in American sheetrock-over-studs construction. And the downfiring sub can load the room radially and reflectively, instead of mostly reflectively in the case of the rear-firing sub array. And not least, the single 12" cone can speak with one voice rather than the inevitable blurring of detail that accompanies four drivers even if they are matched (my primary complaint with linesource speakers).
As for cable, I don't believe it's absolutely necessary to have a single-brand loom for your system. All cables bring specific characters and you may want to use them selectively to tune anomalies in specific areas of the system, but when you can find continuity within one line, that's good. My Druids system has early Druids that have been upgraded over the years to v4-08 status, but they are early enough to have the Speakon connector Zu originally fitted as standard, to preserver their B3 cable geometry all the way from the FRD to the amp terminals. Since those speakers also have the Cardas clamp for spades, I years ago listened to the comparison of Zu Ibis cables connected through the Cardas clamp and via Speakon. My Druids are internally cabled with Ibis. For me, the simple preservation of B3 all the way to the amp is audible and favorable, so I'm glad to see it brought back to Def4. Whether you chose the character of Mission or Event or older Ibis Zu speaker cables, I definitely advocate going with a Zu speaker cable via the Speakon for full B3 geometry.
That said, a friend or mine who had Def2s with HO drivers chose the excellent and really beautiful sounding Auditorium 23 speaker cables, which use low-mass bananas and are natural-fiber jacketed. I will hear his Def4s soon and will compare the Aud23 via adaptor, with Ibis B3 via Speakon and let you know the difference. Cables are the least urgent thing to get right.
Further, Zu cables have a common thread of neutrality running through them, regardless of grade, so there's no problem mixing Event and Mission, according to expense or choosing one over the other for portions of the system. My systems have Mission in specific places where that's the right interconnect for phono and getting three turntables with five tonearms and multiple transformers and phono stages in two systems wired up, Varial elsewhere, and Ibis to speakers. I even have some custom-made tonearm cables made from Cardas 33awg shielded wire in the mix. When listening, no one is looking to scrutinize the cable loom.
Phil
The downfiring sub driver has several advantages, in no particular order: In Def4, the driver is bolted to a 1.5" thick machined aluminum plinth, plus it's a cast-basket 12" driver. Mounting the sub driver to an equally rigid rear panel would require a much larger slab of aluminum or alternate material to achieve the same management of the driver's motion energy on a more expansive panel. Additionally, by mounting the driver in the plinth, the opposite wall is small and stiff rather than tall and large, so cabinet resonance is more easily controlled. The cone motion can't rock the speaker cabinet, either. Then, consider that the soundwave is projected toward the floor, which is generally a stiffer, less resonant surface than is a wall behind the speaker, at least in American sheetrock-over-studs construction. And the downfiring sub can load the room radially and reflectively, instead of mostly reflectively in the case of the rear-firing sub array. And not least, the single 12" cone can speak with one voice rather than the inevitable blurring of detail that accompanies four drivers even if they are matched (my primary complaint with linesource speakers).
As for cable, I don't believe it's absolutely necessary to have a single-brand loom for your system. All cables bring specific characters and you may want to use them selectively to tune anomalies in specific areas of the system, but when you can find continuity within one line, that's good. My Druids system has early Druids that have been upgraded over the years to v4-08 status, but they are early enough to have the Speakon connector Zu originally fitted as standard, to preserver their B3 cable geometry all the way from the FRD to the amp terminals. Since those speakers also have the Cardas clamp for spades, I years ago listened to the comparison of Zu Ibis cables connected through the Cardas clamp and via Speakon. My Druids are internally cabled with Ibis. For me, the simple preservation of B3 all the way to the amp is audible and favorable, so I'm glad to see it brought back to Def4. Whether you chose the character of Mission or Event or older Ibis Zu speaker cables, I definitely advocate going with a Zu speaker cable via the Speakon for full B3 geometry.
That said, a friend or mine who had Def2s with HO drivers chose the excellent and really beautiful sounding Auditorium 23 speaker cables, which use low-mass bananas and are natural-fiber jacketed. I will hear his Def4s soon and will compare the Aud23 via adaptor, with Ibis B3 via Speakon and let you know the difference. Cables are the least urgent thing to get right.
Further, Zu cables have a common thread of neutrality running through them, regardless of grade, so there's no problem mixing Event and Mission, according to expense or choosing one over the other for portions of the system. My systems have Mission in specific places where that's the right interconnect for phono and getting three turntables with five tonearms and multiple transformers and phono stages in two systems wired up, Varial elsewhere, and Ibis to speakers. I even have some custom-made tonearm cables made from Cardas 33awg shielded wire in the mix. When listening, no one is looking to scrutinize the cable loom.
Phil