Yeah, sorry I looked at them with a phone first, but now on a computer (with TV as a screen) and I can see the differences better. The HDs of nth orders are different for sure and some are lower as well with the passive filter. Also the THD seems to be lower on average for mids, although part of the highs have slightly more distortion. The 2nd is the dominant and 3rd is high enough to be audible in some parts. As always, pushing down odd orders is recommendable. Anyway, if the goal is to reduce HD, shouldn't THD be lower too, otherwise there would be no point in doing it, right? It would make the graphs more readable if you left out the highest order HDs, because it's so low anyway. Maybe up to 4th would suffice?You and I clearly have different interpretations of the data. Noise dominates at very low frequencies, so that's mostly what you're looking at below ~40Hz at 96dB and 103dB, or ~70Hz at 86dB. The 2nd harmonic is not strongly affected, but is generally slightly lower with the filters except around 2kHz. The 3rd and 5th harmonics are significantly lower at most frequencies above 350Hz at 86dB and 96dB, with the exception of around 1kHz at 96dB (due to a mechanical nonlinearity in the compression driver, I believe). The woofer's 3rd harmonic drops nearly 10dB in the top octave of its passband (500Hz-1kHz), while the tweeter's 3rd harmonic drops ~5dB above 2kHz. There seems to be less difference at 103dB compared to the lower levels. At the moment I'm not entirely sure why this is.
A small note regarding perceived sound quality:
First, this is just based on sighted listening so I fully accept that what I heard could be entirely the result of bias. I didn't expect much audible difference besides a reduction in hiss (which was mostly inaudible anyway) as the measured harmonic distortion (>H2, anyway) was already pretty low. However, the more I listen the more I'm (cautiously) convinced that the sound quality is improved. In particular, I've long noticed a low-level "grit" in the sound which was particularly noticeable with certain instruments—piano perhaps being the worst offender, especially if the recording had a generally dark/warm tonal balance. This impression persisted across multiple systems that I built, all having only digital filters. With the added passive networks, this "grit" seems to be absent or at least notably reduced. So what's going on? My guess is that the dominant factor in this case is a reduction in hysteresis-related distortion. Or I'm fooling myself. Could be either.
Also another thing. The Purifi article is about filtering out resonance peaks. And to be precise, filtering them with series resistance (reducing current at desired frequency) instead of shorting to ground with a parallel filter (directing the current elsewhere). That surely is theoretically the better approach of the two. That can also be done with a DSP, if you got dedicated DSP channel for each driver. When creating notch filter equivalent with DSP peaking filter of high Q, you get essentially the same effect. Even group delay and phase will be similar if the transfer functions match. Also since DSP works in reducing the signal (reducing current), it should reap the same benefits as series notch filter for taming resonance peaks, because instead of resisting, there is less current to begin with. Can you test this theory out? It should behave in the same manner as in the Purifi article, so if you add multiple peak filters for multiple frequency points, you need to start with the lowest and measure each step.
And one more thing. During current drive experimentation, some have said that woofers sound quality suffers from series resistance. That can be due to the damping factor being lower and the woofers inertia is less controlled. I fail to sees how this does not apply to mids and highs as well, maybe the excursion distance is critical there. But it's nevertheless worth experimenting on if you got time. I can see you have made quite complex passive crossover considering you still have the active filters backing you up. Intuition suggests that reducing the number of passive components would give better results. I would suggest trying simply nothing but series resistors (something in order of 20-40 Ohms for an 8 Ohm driver) and then again added with DSP resonance control and see how they do.