My Ncore and all new cables are pretty thoroughly burned in now after about a week. Speakers are 88.0 dB actual sensitivity. Room is 3200cf, w-w carpet, light treatments @ usual suspect points.
This is a unique comparison because in both cases the loads are identical except for impedance load and about 2' of wire. A potential down side is I performed the test in mono only, but results would only magnify in stereo.
The mono source was not simple summed mono L+R but rather the Center Channel output of a pure analog Trinaural processor. (I'll test the Trinaural later for transparency to the source. The Trinaural should have a simple "stereo/bypass" selector but it does not, so I must improvise one.)HERE'S
the speaker load, my own unique evolution of Toole and LeJeune's earlier work. If you decide to perform this test yourself with two stand mount monitors setup in the described array, employ either the L ch or R ch alone for mono source, don't sum the L+R channels together because of the resulting phase anomalies.
If you assemble two stand mount monitors as per the above instructions, toward the goal of replicating the test, 8 Ohm nominal monitors is ideal. Two 8 Ohm nominal monitors will switch from 4 Ohm nominal (parallel) to 16 Ohm nominal (series). The title specs are as indicated, the minimum impedance, far more critical to results rather than nominal impedance.
The 4 Ohm load does indeed draw 4x as much current, and your cables must meet this spec, which mine easily meet. The sum total cable difference was about 2' extra cable in the 4 Ohm load.
Note: compensate for the amp playing +6 dB louder in 4 Ohms vs. 16 Ohms. My preamp has 1.0 dB steps in the analog mode employed.
Two 4 Ohm monitors setup as directed would switch between 2 Ohm and 8 Ohm. In the 2 Ohm mode I suspect the minimum impedance will be too low. You might risk Ncore damage, I don't know. If you do the test with two parallel 4 Ohm nominal speakers, do not exceed moderate levels. Too low SPL may skew test results. In my case I played a well recorded Telarc orchestral piece at good levels.
Sorry, I kept the subs on, active crossed at 70 Hz. Playing full range would only increase the differences though, certainly it would not decrease the differences.
Sorry for such a long drum roll...Well, I'm hear to tell you, the 10.6 Ohm minimum load absolutely annihilated the 2.65 Ohm load. The orchestra went from drumming along like the leader took a break, to having drank a couple large cups of my morning brew, not the strongest on earth, but it's up there. Stage about doubled in size (yes, this array even in mono makes a huge stage, believe me), greater instrument separation, detail, smoothness, timing, it all improved and not a wee bit. Dynamics were completely different. Much more "interesting" and alluring, yet if anything, less fatigue because it was just so much more interesting to hear. Really, they sounded like they played flat and with different instruments in 2.65 Ohms. The biggest difference was likely "sound density", a quality in which this speaker array may be supreme. The low impedance load by comparison was "thin" in density, not spectral balance, which was virtually identical. The high impedance load, by comparison, sounded like the effect of switching to an absolutely killer big, particular anatomical part big, ultra transparent tube amp, in the very best sense of the word. Highly dense, but still transparent (even more transparent than the low impedance).
Sorry, I don't know about my speaker's phase angle, but suspect it's not too difficult. IIRC every test amp drove them well, especially Ralph Karston's sweet 30W stereo OTL.
With the 80 Hz active high-pass filter, this speaker has only one minimum impedance dip centered at 200 Hz, stretching from about 100-600 Hz. Above 600 Hz the load is flat nominal.
I'm not saying Ncore is generally ill-suited to lower impedance loads because, well, every application is unique as anyone with experience can and will tell you. This was one test.
But I'll never bother again with the 2.65 Ohm minimum load except to prove the point to a visitor.
Powering the 2.65 Ohm minimum load Ncore runs out of current before voltage (specs indicate about 500Wrms).
Powering the 10.6 Ohm minimum load Ncore runs out of voltage before current and always has an easier load hence sweeter distortion curves (I presume). Ncore makes a maximum of 100W above 600 Hz with a slight power reserve (about 2 dB, 160W) at the impedance dip of 10.6 Ohms centered @ 200 Hz.
I wonder if there is any difference between peak power into the two different loads. I'd bet nothing or insignificant. But there's probably big differences between the peak and average power capacity: Into 2.65 Ohms the peak and average power are likely very close. Into 10.6 Ohms I bet there is a big difference between peak and average power. Music is dynamic and this might explain why 10.6 Ohm sounds louder even though it's not. I seem to remember months ago Mike Galusha posting that, into 4 Ohms, Ncore's peak and continuous power capacity are pretty much the same.