- Apr 22, 2016
- Princeton, Texas
Would it be accurate to assume that the M2 waveguide "pinches" the waveform in the horizontal and vertical plane? It looks like two sets of fingers is pinching the mouth.
I remember reading somewhere that Charles Sprinkle no longer believes in constant directivity as the best solution and that he now thinks smooth but steadily rising directivity is preferable. I asked directly and he said it had a lot to do with needing a high-shelf filter from around 2khz with the JBL M2 in normal/small rooms to sound natural that led him onto that path.
The approach I use is constant directivity but with a gently downward-tilting direct sound, instead of a "flat" direct sound. In my opinion this gives a natural-sounding tonal balance while minimizing the spectral discrepancy between the direct sound and the reflections, which in turn is arguably beneficial to timbre. My designed-for listening axis is about 20 degrees off the horn's centerline (after Geddes), so there is some tilt-down of the highs in the direct sound already happening. The horn's inevitably slightly "hotter" on-axis energy is actually making its first appearance at the central "sweet spot" as reflected sound, thereby tipping the spectral balance of the reverberant field up a bit, which reduces the net discrepancy between it and the direct sound.
Of course I realize this goes against Harman's findings of what listeners prefer (flat on-axis, tilt-down off-axis), and unfortunately for my credibility, it also goes against what Charles Sprinkle now believes to work best. Hmmm. Don't tell my marketing department, they'll demand a bigger budget.