HT cross over question

OP's KEF 104/2 speakers need to be supplement by a sub for LF extension. If Op uses an 80 Hz crossover and equal levels to all speakers, the transition to the sub should be imperceptible.

db

i suggest NOT going through inferior sub cross, and simply go full range direct for stereo, and maybe run sub from parallel speaker connections for music duties. then, id run sub line level n crossed over from Yamie processor for movies, also crossing over mains from processor setting in yamie to match for movie applications! keeping sonic midrange n treble purity is key, and then necessary processor internal EQ for the MORE demanding dynamic ht duties, is critical,

Db I hear good results setting the sub up as you suggest playing music... very pleased with dropping the kube 2000 out..

Avgoround... The problem is the flexibility in connecting the sub . I prioritize two channel music. so the amp takes balanced outputs from the pre and the sub gets the full range pre amp out put to the single ended LR inputs of the sub and cross over as Db suggested.

When I run the Home theatre... I use the same single ended pre amp outs to the sub... set the sub cross over and high pass output to 80 and flip the amp to uses single ended inputs now coming from the sub. its a bit congested but it is a movie..

Everything I read about the sub warns you about using both the high level speaker inputs and the low level single ended inputs. I don't see how I can avoid this setup. The only sub that seems to be able to set up using both inputs are the Rel brand which appears to let you toggle between the two kinds of inputs.

Historically, crossovers built into powered subwoofers have been anything but sonically pure regarding passing midrange/high frequency signals!..degrading overall sound quality to the monitors. Thus, bass is least of my concern in 2 channel music, and keeping the purity of the delicate mid and upper registers is paramount, and i'd default to running speaker level through a switcher top the powered sub, and defeat that for movie playback, if it where me. Again, I would venture that any AB comparison for sonic purity of mid/hi, going both through the sub woofer crossover, and without it, would easily be a discernable advantage,if you NIXED the sub's mid/hi-pass crossover in the mix!!
Nope, seriously doubting that's the best route, IMO

See here in lies one of the problems, in that you're attempting to do a dual purpose system, and you want convenience, and the sonic advantage of a dedicated outboard 2 channel pre plus outboard AV processor working in the same system - which you will have to switch the later in and out of the system anyway. It's a compromise of convenience to isolate the better 2 channel pre-amp for music duties in the setup. This causes a dilema in how one chooses to deal with how the powered subwoofer is to be used in both systems simultaneously, and remain effective for both. And, I find, you either often end up compromising the perfectly flexible and integrated subwoofer transition while swicthing between the two systems, or you maintain the best integration of mid/hi freq sonic purity whilest switching between them, and maybe have a not so convenient subwoofer conversion between the systems! Neither is likely ideal, and has it's pro's and con's in an ideal world.
If HT was my priority, I'd be likely nixing the seaparate 2 channel analog pre amp all together, and simply go with a high end digital AV prepro, and just process my music internally in the DAC's in the pre, with all digital connections, and analog converted or passed direct when you do tuner, turntable, etc. There are a number of them out there, that still sound superb for most people's tastes and applications, such as in a custom integration setup.
If music is your priority (such as yours), I'm probably doing what I suggested, and simply throw a speaker level switcher to switch in and out of the way for the subwoofer in parallel connection for music, and going straight out of the analog 2 ch preamp for music, running the sats full range. (the line level is disconnected when the AV pre/pro is turned off and not in use). Then, when it's movie time- and the AV pre is on and looped in to the 2 ch analog pre - you simply are using the internal digital 80hz crossover to all channels, and the subwoofer is filling in the bottom from the LFE output of your processor -and simply switch the speaker level out of the way from the switcher! Seems pretty straight foreward to me.
Again, this way, I get pure sonics to my sats for full range music, and get to add bass run in paralell. No other crossovers will do anything but degrade my signal purity that im asking out of my expensive analog 2 ch pre, otherwise.
But hey, that's me