Reproducing the fundamental of very low notes is unnecessary (Greenboy, the designer of fEARful cabs, purpose built to amplify down to F#0, has stated this, as do experienced ERBassists), you imply it needs to be reproduced.
It is fun to reproduce the 'felt but not heard' fundamental if you want, with high powered expensive specialist sub-amplification, but the audible tone is absolutely fine without it.
Most amplification does not even reproduce the fundamental of B0 at 31Hz but it still sounds good.
In fact, even the common E1 has a fundamental frequency poorly reproduced by most amplification (40Hz).
But i expect you know all this as i seem to remember you have a good grasp of science.
I do have a good grasp of Science (Acoustical Physics degree), and the Engineering necessary to do Pro audio - I design that kind of gear for a living, and have done so for a very long time at this point.
Reproduction of the fundamentals of low notes is...difficult - it requires large boxes, lots of power, lots of surface area, etc. People who make bass guitar cabinets deem it "unnecessary", because...it just isn't practical to do in a rig what you put in your trunk - they focus on efficiency (so you can hear yourself), as well as low weight and size, and the thing that always suffers (you can't have all 3 at once) is low frequency extension. Yes, they are poor at even a low E - the original SVT rigs miss that entire octave; they don't really start until about 80Hz - the E above your low E. Since most bass players are used to the experience of a bandwidth limited rig, they are used to the performance that delivers.
The whole high pass filter thing is twofold - there are 2 major reasons to use a high pass filter:
1) Magnetic pickups don[t have a low frequency limit - they can make VERY low frequency sounds. When you pluck a string, the initial transient contains sub-audible signals, which if they aren't filtered out, will waste power and cone movement - it reduces your headroom drastically in the worst cases. Any decently designed bass amp has a high pass filter that will at least do some of this filtering. Any FOH person worth a darn will put a high pass filter (at sub audible frequencies, not 60 Hz) on a bass channel for this reason - the sub cones are expensive, no sense risking them to reproduce things you can't hear.
2) For a bandwidth limited rig (like a bass amp), asking it to reproduce things it can't is a similar waste of power. It isn't the low frequency content that causes "mud" - if the rig is capable, that sounds/feels wonderful, and doesn't sound the least bit muddy. The mud in many bass rigs comes from speakers that can't handle that low frequency content. The "mud" you hear is not the fundamental frequencies, it's higher frequencies caused when the speaker (and/or the amp driving it) distorts the incoming signal, adding unwanted harmonics to the intended signal. With a very capable PA, you don't want or need high pass filtering for this purpose - the rig can handle it, and the result is more impact.
Some of us are fortunate to get to play through (and in my case run FOH for) PA's that are very capable in that area. The impact of such a PA is, once you've experienced it, undeniable. You simply won't get that from your bass amp. Is it necessary? For me, yes. The gigs I play at and/or do FOH for), we have audio standards that are well above your typical bar gig. It's not about being loud - it's about being impactful. Low frequency extension is a huge part of being impactful with audio.
During the shutdown, I've played a bunch of "virtual" gigs. I played 4 string basses for most of those gigs, because the sound is coming through someone's home speakers. Those aren't going to really do a low B justice; better to play what will be heard and work around those limitations than to play a bunch of notes that won't be...experienced the same way as what I'm hearing when I play them in my headphones.
