Well, I finally got the Kappas moved in to my space and set up, and so far I'm really enjoying them!
After breaking them down, packing them up, having them transported, unpacking, and setting up again (all with help of course - these things are ridiculously heavy and unwieldy), I'd say the best news is that they survived! My goodness they are heavy and unwieldy. If I hadn't inherited these for free (my father passed away recently), I'd never even have considered buying a pair.
At any rate, I ran low-level 20Hz-20kHz frequency sweeps on each channel separately and heard nothing weird - no obvious volume changes, no rubbing drivers, distortion, or extra frequencies that weren't supposed to be there.
When I first started playing music, I got totally spooked - the sound kept muting every few minutes and I thought my Purifi 400-based amp wasn't up to the task of driving these things after all. After 20 minutes of this, and being part way through typing a version of this comment where I was asking about amp recommendations, I remembered that my Mac mini-based streaming setup has always had a weird little bug that only crops up when it's been running uninterrupted for weeks or months: the Music app just stops outputting sound after about 2 minutes' worth of playback. Fortunately that was the issue, fixed by a restart.
So far I haven't pushed them really hard, but they seem to be doing fine at SPLs in the low 80s from my 3-meter listening position - which if I have my math right means they're putting out about 92dB SPL at 1 meter. That's plenty for my everyday listening volume, and it's 3-5dB from my personal preferred max volume so I'm feeling pretty optimistic.
And I'm hearing something with the Kappas in my setup that I've never heard before in the 30+ years I heard these speakers in my parents' house: silence! No hum from the power amp, no hiss from the speakers. Just total silence. It's very cool.
I do have some questions for
@Doodski and all the other knowledgeable folks here:
1. I took my graphic EQ out of the circuit, which allowed me to go to fully balanced interconnects: it's just my Oppo UDP-205 to the Audiophonics amp. This has radically changed the gain-staging: where I used to have the Oppo's volume in the high 70s to low 90s, it's how in the high 30s to mid 40s. I have the amp in its high-gain setting (26.5dB). If I were to reset it to its default (20dB), would that have any beneficial effect on the amp's ability to drive the Kappas? I know lowering the amp's gain will slightly increase its measured performance, but I don't care about that since it's already a stellar performer at its highest gain.
2. I've been pleasantly surprised at how nice these speakers sound with no EQ in the chain - but I am thinking of getting a MiniDSP SHD to put between the Oppo and the power amp so I can really get the in-room response as good as it can be. Is the MiniDSP designed to operate at unity gain, or is it inevitably going to increase the level of the signal going into the power amp? Is there any particular gain-stating configuration that would make the speakers as easy as possible for the power amp to drive - or is the final SPL in the room the only thing that matters?
3. Finally, the Kappas have 4 dials that can be used to alter how the crossover network works - the relative volume of the various drivers. I was shocked to discover that my father had all the dials set to minimum. I reset them all to the factory default of flat/nominal, and they're like whole different speakers. I can tell that this all-flat setting will need to be adjusted a bit, but if @Doodksi or anyone else has any advice or recommendations on which of those 4 dials to start with, or where to start fiddling, I'd be grateful - because it seems like a lot of dependent variables there.
Oh - and I have the Extended/Normal switches to Normal, and the speakers seem to have plenty of bass for my taste. Once I get more confidence in the amp's ability to drive the speakers fully, though, I'll experiment with the Extended setting.