Many PA speakers run full range through their 12inch (or +) main drivers, and just protection against their tweeter / horn whatever. And this is live music, which is often recorded to reproduce on our 'hi-fi's' for live event reproduction at home.
I see this come up a couple times here. It's worth making some distinctions:
Most of this site deals with hardware for
music reproduction. The main priority here is fidelity; the music has been made, there is a source of truth, and the point of quality music reproduction equipment is to regenerate the original as much as possible. There are other priorities but fidelity is paramount.
The act of
music creation is significantly different. There is no source of truth beyond what the musician hears in their head. The signal chain may be their bare voice into the aether, an acoustic instrument, or a long string of devices out to and including amplified speakers. Generally equipment is included in that signal chain
specifically to alter the sound in some way.
So for instance, you have a guitarist, they have the guitar and its components, the strings, the pickups, pedals and processing, amplifier, speakers, cabinet, all are a part of the creation chain, all have their own frequency response, output limits and compression, resonances etc. Equalization and other effects in this chain can be dramatic. Guitar speakers and cabs are frequently
pretty bad at reproducing sound but that's OK and a deliberate choice, as the colored and distorted output is a desired effect.
Guitarists commonly don't use multiway cabinets as their frequency band doesn't really require it, but bass guitarists do, as do keyboardists and some other instrumentalists. These cabs will have crossovers of varying complexity based on cost and task, from a cap on a piezo to far more sophisticated circuits. However, the cabs often aren't designed for flat FR - in fact, flat FR is generally undesirable vice a 'baked in sound' that improves efficiency and adds character. That's also why it's very common to mic the cabs instead of pulling a DI line out from the amps, or to pull both and mix them.
There is a slight exception here with a modern concept of modeling, where the musician has a single component that 'models' the desired signal transformation (say, to simulate an old '60s cab and tube amp) and then the rest of the chain including the speakers are intended to be full-range flat response, to avoid further now-undesired coloration. At least right now this isn't mainstream for various reasons. Also, understanding speaker dispersion is a thing that is out there in this context but generally not well understood or prioritized.
Slightly different from music creation is
music reinforcement, roughly i.e. the PA. In live reinforcement the sound engineer is as much an artist as the weirdos on stage, and the instrument includes the room / arena and all its contents. Reinforcement has a variety of priorities in communicating the artists' intent roughly evenly across the entire venue, which is a much more complicated task than just putting sound in the 'sweet spot' between a stereo speaker pair. So there may be arrays of drivers for different frequency passbands in complex arrangements for power shading etc.
Your
really cheap (or really old, although most quality stuff of even 50+ year old vintage had some sophistication here) PA setups might just have a cap on the horn of a passive speaker, but when it comes to processing for sound reinforcement, the sky is the limit, so as you go up in cost and venue size this almost immediately turns to DSP and multi-amping, in the speaker cab or upstream.
Also with live music presentation at the creation or reinforcement level you have a whole bevy of priorities like, the gear must work under harsh conditions every night, it must produce SPL levels that blow your house windows out and get you arrested, it must do this with a much more aggressive duty cycle, it must be reasonably portable, it may have to work outside in inclement weather etc, that just don't apply to the amps and speakers in your living room. The degree to which flat and clean frequency response is important can vary quite a bit, along with stereo positioning etc.
So there is a tremendous amount of sophistication and complexity out there, just understand it may or may not overlap with audiophile priorities.
Pic attached is a bass cab crossover I built, the FR isn't all that flat, but the priority here (besides cost) was taking a kilowatt of power for an hour or two without me needing to think about it.
) behind crossovers frustrates me.
