(I am a semi-professional sound guy) -

Saying a PA system 'just sucks' is a bit of a blanket statement. Given how incredibly complex audio actually is, and how little people want to pay, it's sometimes surprising it works at all.

(I'm not trying to be defensive here, or argumentative, in case it sounds that way...)

Yes - a lot of PA systems are cheap, nasty, and stupidly designed, but quite often they're fine - just our expectations of what is possibly with them is somewhat against physics.

Bass is pretty unintuitive. Due to the very long wavelength (100hz is around 10ft give or take), if you try and use a stereo system to produce bass frequencies, you do get all kinds of troughs and peaks where the system ends up cancelling things out. Peak sound from one speaker reaches a point in the audience at exactly the same time as trough sound reaches that same spot, and the sound is cancelled out. Half a meter away in one direction, you get both peaks, and they add together, and half a meter in the other direction and you get something else weird. And this happens differently with every single frequency. Above 200-300hz or so you stop really noticing it, but below that it's horrible.

A lot of that can be solved by using a single point source for subs (bass), thus the 2.1, 5.1, etc systems. (The .1 means a separate bass subwoofer).

The trouble with doing that with a large enough system, is that you now have phase issues between the subwoofers, and the mains.

Say your subwoofer is set to only reproduce sounds up to 100hz, and your mains are set to only produce sounds above 100hz... You still have an area where both the mains and the subs are producing that sound. It isn't a binary state of producing or not producing sound.

So if the subs are (say) 20ft from the mains, (in a triangle configuration, with the subs on the floor) then you still will get phase issues with either full out cancellation in places, or else very messy comb filtering which also sounds crap.

Sound moves quite slowly (again, extremely roughly, 1130ft a second). So say a guitar is coming out of both mains, and because you're slightly to the right of stage you are 10ft closer to the R than L, you hear the sound twice, first from the R speaker, then 10ms later, from the L. 10ms is right on the border of you being able to tell it's a separate sound, so it doesn't sound like an echo, just a single slightly muddy sound, coming from slightly left of the main R speaker. (Wikipedia the Haas effect, if you're interested). This is one of the problems with stereo sound for a big live PA - only very few places in the audience will actually be able to experience the stereo effect - most will only get mono, realistically.

In a small domestic system where the mains are only a few feet from the sub, you don't notice it. In a big set up, you do.

You can get around a lot of that by flying your subwoofers. But then, as you don't get the 'floor carrying the bass' effect where the sound is literally moving along the ground, you need to use much more powerful bass amps and speakers to get the same kind of feeling.

My preferred solution is called 'aux fed' bass, where you send sound to the sub(s) from a separate mix than the main L/R speakers. Then I'll send the bass, kick drum and perhaps a few other things directly to the subs, and nothing else. This has many advantages, you get a lot less of the 'pop' sound from microphones when people are talking, the bass tends to sound a lot cleaner (as the speaker isn't vibrating along with every other sound), etc. However, it's a lot more complex to set up, and if you're playing back backing tracks or pre-recorded music that isn't mixed for it, it'll usually sound quite messy.

This is where the separate PA per instrument thing can help.

The trouble with that is how complex it is to control, how much space it all takes up, sight lines, and so on.

The article really didn't go into how hard it is to stop feedback when your speakers are behind the mics. That's why they had all that insane multiple mics out of phase stuff.

That's why we normally put the main speakers in front of the stage. You want them as far away and pointed as far away from the microphones as possible.

But if they're in front of the stage, then you want them as small and out of the way as possible, so as to not muck up people's sight of the stage / screens / lighting, etc.

At the end of the day, live sound is all about compromise. There are no perfect systems, rooms, bands, audiences, or engineers. If possible, we try to make as many people happy as we can. If that includes whoever is paying us, that's usually good. If it includes the band, that's even better. If it includes the audience, well, that's just a bonus, really. :-) (It'll probably never include the sound engineer. We're all grumpy old sods and never happy).