Speakers were designed to be run full-range.
Then most speaker designers either have no understanding of the term "full-range" or are truly incompetent. Or both.
You don't really understand how a speaker works, then, do you? A speaker with a low-end F3 of 60Hz for example, doesn't disintegrate when it's sent a 20Hz signal; it just doesn't reproduce that low a frequency with any audible output, if any at all.
This isn't entirely accurate. While a speaker won't automatically fail when sent a deep bass signal (this depends on signal amplitude among other things) it will be forced to react to the signal sent to it regardless of whether it can or cannot reproduce that content. As frequency drops, impedence drops (resistance increases), the more cone movement and power required at low frequencies.
The laws of physics still apply. A sealed speaker acts like a high-pass filter below resonance. It doesn't have to respond to signals below it's resonant frequency because it acts precisely like a high pass filter. Ported speakers do not. The great majority of speakers on the market are ported
I really don't understand where some people get this idea that just because a speaker can't physically play back deep bass frequencies well that somehow it won't respond to a high amplitude signal containing deep bass below it's passband. It goes against reality. And the reality of the situation is that just because a speaker might not generate enough output to be perceived at a given frequency does not at all mean that it won't be forced to react to said signal whether it can reproduce the content or not.
The only exception to this would be in the case of ported subwoofers with built-in limiters (or servo controlled) to prevent overexcursion, but we are talking about speakers with no high-pass filters used. I think that some people here are also forgetting that there is substantial
low frequency energy in the main channels alone in many sound tracks. Spectral charts show evidence of sub-20 hz material at high amplitude (and even below in some bizarre cases) in more and more film soundtracks and that should be reason alone to be more cautious when deciding to use the 'large' setting.
Dolby wasn't kidding with their 20hz low frequency spec.
Speakers that aren't capable of it will simply not reproduce those frequencies.
The speaker might not be able to reproduce those frequencies but that doesn't mean a thing. It doesn't mean that it won't react to the signal being sent to it. The amplifier doesn't all of a sudden ignore the signals and magically hide them from the speakers. Not only is it naive to think so, but it goes against how amplifiers and speakers actually work.
There is this thing that no one can avoid and it's called the laws of physics. A woofers pistonic motion will be increasingly non-linear as soon as it's motion exceeds it's linear excursion (VC outside the gap), and high amplitude bass at deep bass frequencies is one excellent way to achieve overexcursion. Not to mention that impedence will drop like a ton of bricks at very low frequencies especially with most AVR's. How this will affect the speakers mechanical action should be clear to anyone with even moderate understanding of mechanical systems.
Try playing back 'Master and Commander' with AVR (or pre/pro) setting to large in conjunction with the LFE at high levels. It's bad enough to try this with 'large + sub' with speakers with moderate excursion levels but in conjunction with the LFE track it's practically suicide for most speakers without a sub. This is
volume dependent to a degree but I warn those who think that reference level volume is required for driver failure. It most certainly is not !
They have a natural roll-off.
No they don't. I don't know where you got that idea from but unless you are talking about sealed designs, speakers most certainly do not have a natural roll-off. Ported designs have a 24 dB per octave drop below tuning which borders on supernatural.
Just how many people have sealed speakers for main speakers ? Few, I would imagine. Ported speakers bottom out so easily as soon as you feed signals with high amplitude, low frequency bass. And one doesn't have to play back at so called "reference levels" for this to happen either.
Just adding a few cents.