I changed up my sound a bit this morning. Went down early, woke up early. Goofed with cabling while sipping coffee.
I had all my speakers in parallel running things via dual mono SE84s. System took it and it sounded OK. I don't play loud.
This morning I removed my second set of 15s, floor slam facing, from the mix and now I am only powering the 8" and one 15" per side with the dual mono amps.
More favorable impedance load, for certain. I'm back to just under a 4 Ohm load on the mono'ed SE84Cs. 8 ohm JBL+Visatos 6 ohm (this is how they reach imaginary efficiency ratings to publish. Still like the drivers, though)
I definitely lost some air movement in the low end by almost halving my cone radiating area in the lower range. I listened in stages with music and (I am unusually familiar over many years of over exposure - I know which one Pink is. He's the tool) pink noise. I am only afraid of noise that I did not create, otherwise I can deal with it and use it.
BUT, I have now added my McIntosh, using the out from the SE84Cs (made up the speaker out to input adapter many years ago) and I am using the floor slam driver as a sort of subwoofer, still same "L" shaped baffle, still connected mechanically at the magnets. Still receiving the same/coherent power signal. Still need to rebuild the baffle in solid hardwood, etc.
But the floor slam has considerably more power available, now.
These FAT and flat-ish 15" drivers measure 8dB down at 500 Hz, in part because I tried to build them to do this and got close. I would love if the high drop off began a bit lower.
I am trying to avoid adding a crossover. I have a spare Crown, which publish measurements at 1/10th the distortion compared to the other items in the system, except for the preamp.
I gave in and I am trying out the crossover on the "floor slam sub woofer." ... all open back, still.
The lower 15 is still wide open on the bottom end, no safety high pass of any sort in the system, but rolled off up top now beginning around 45hz. Still tweaking that number, but for now it seems to be an improvement in low authority, but also clarity and definition to the whole overall sound.
Taking some of the burden off the two Mono amps surely adds something to this improvement.
Having "half" my lows pointed downward has definitely changed the shape of the typical bi-directional cardiod pattern you expect with an open back system.
I haven't tried to put my 60 degree mic on anything yet and determine patterns, but just walking in the room things are different.
Sitting and listening, things feel better, regardless of what piddling with mics could possibly tell me later. It feels better.
I'm going to keep trying and listening to things with this set up for a while longer. First impressions are positive. Still going to measure at some point, but not today.
Today and for a while I am just going to listen and maybe play with the crossover and the McIntosh toward the best balance with the uppers.