No reason to argue. I didn‘t convey my point, but you read the plot.I'm not going to argue until you can make some sense. Instead, I'll lecture.You post a chart of a 42Hz fundamental with what appears to be a significant 12Hz rumble component. Depending on the slope of the filter, even a modest filter with a corner of about 20Hz could be expected to smash that down a lot. So, I quickly modeled up a small ported bookshelf speaker with a Focal midwoofer I had some specs for (around 3mm Xmax), and loaded it into a small box ported to 40Hz. Power handling is okay and the cone motion is fairly controlled until around 33Hz. Below that, it quickly turns ugly. At 12Hz, it can take almost nothing. At 20Hz, it can take about double the power (which is still is not much). 12Hz could destroy the woofer. Now, apply a second order filter with fc=25Hz. What was out-of-control, woofer destroying cone motion at 12Hz and 10W into the speaker becomes probably a non-event. That is still a bit too much for this tiny speaker, and some might argue a 30Hz corner might be better. But guess what? Some cheapo products like a Schitt designed for cheapo speakers like this offer just that--actually, an even higher selectable corner frequency, should you want it.
I think the Precision Phono is probably around a 20Hz second order. Even that would increase my little hypothetical speaker's power handling at a 12Hz rumble frequency from about .75W to 7W. Cone excusion is cut by about 70%. Since the rumble is a fixed component not really tied to the music, in acoustic terms, that's double the volume for the rest of the system (with a filter you say is too low and does not work). But, a 20Hz rumble filter works just fine. Why? There is nothing to suppress from 20Hz to around 35Hz. If you have this problem in the Fosi? Well, you're just screwed if you try to play loud. You can't turn up the music without blowing the woofers.
So, stop telling people rumble filters are "blatant nonsense". In my example, I just saved my speakers and kept on crankin' it and rocking by pushing a button you say I didn't need and would not work unless it was at 50Hz. While a third order filter at 20Hz would be ideal, or a second order at 30Hz, a second order filter (12db/oct) around 20Hz probably does get the job done even on small bookshelf speakers.
There‘s some content at 13Hz, which obviously originates in the basic tonearm resonance. And there’s more below. Of course that could run a ported design into mech/ overstress. We don‘t want it to reach the speaker. Question is, how to achieve this.
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It could be attenuated at the tonearm. My Denon DP37-F does it with some success. A Shure pickup with the ingenious brush also would operate under improved conditions. Not the least, the suspension of the pickup‘s cantilever could be damped, like the Audio Technica AT3600 shows. I acknowledge that this would rather keep the stylus in the groove, but not attenuate the resonance sufficiently.
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The example you give, in regard to the speaker, is quite illustrative. Some small midwoofer with a soft suspension, used with a reflex tuning at 50Hz. It is optimized to deliver the last dB of as deep bass as possible without equalizer. With today‘s digital sources such a design would run into the infamous un-loading below the tuning with quite regular music. It seems that most records are cut-off at 40Hz, while some more artsy stuff goes down to 30Hz. When taking a spectrum of contemporary content, I regularly see the highest levels at exactly the cut-off frequency. 42Hz is a musical fundamental, that‘s why. By all combined the un-load effect dictates how much the speaker could be cranked up. In order to exploit the potential of the speaker, given contemporary content (non vinyl), a filter addressing the speaker’s specifics is needed. That would happily deal with the tonearm resonance anyway, as a side effect.
Of course my argument comes from an idealistic position. But who am I to excuse shite speaker design? I accept the caveat, that the best passive speakers (Revel, KEF, …) address the problem with tunings at35Hz or lower. That fits the demand for the musical content. (But who was wise enough to consider the factual circumstances?) Well, with those the rumble filter is a reasonable add-on. Actives—protected.
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I concluded, that a rumble filter doesn‘t solve the problem stated in general. What folks need is to avoid those handy two-ways to begin with. Second, all wo/men need an equalizer to adjust the response to the room and listening position. That brings with it an appropriate cut-off filter, addressing the speaker, not the turntable, but solving the turntable issue on the go.
