The bass signal is flat, what you are doing is forcing bass into the signal that was not there in the first place which can and will severely distort and clip the signal to hell especially if you already set your gains to max clean output and no, you cannot hear the distortion or clipping unless you have an extremely trained ear but its indeed there. You definitely never ever want to touch bass boost on anything if you plan on keeping your system healthy for years to come. Manufacturers do that to attract noobs making them think their amp is louder than it actually is but its literally just a clipped signal which makes subs sound louder than they are with a clean signal.
Its better to figure out phase cancellation issues or address enclosure design flaws, box location/orientation over using boosts for a dip in their frequency response which usually leads to blown equipment most of the times.
I'm partial to bass boost. Obviously if your setup is good you won't need it because the enclosure will fill in that dead spot. The input signal isn't what's clipping, it will be the output channel. Like in other scenarios you can check for output signal clipping with a multimeter and various 0db sine wave tones. It's true that it "stretches" the signal, which is always a negative thing for clarity, but I'd rather have a slightly stretched previously clean signal than an overly boomy midbass followed by an underwhelming low bass in enclosures that offer no resonance in the low end. By using the bass boost knob you're sacrificing volume in more efficient ranges and signal clarity for equal volume between high and low in an over-dampened enclosure scenarios. That is if you correctly set it up to avoid clipping. The clip lights make it much easier since you can tune for flat response through sweeps while being mindful of clips.
True, that pretty much gets to the heart of it.
please explain to me how to use a dmm to see a clipped signal?? LOL
Ohm's law to match the rating and avoid it altogether. Voltage goes higher than RMS rating allows, lower gain or boost. Pretty easy, I'm sure you and Google can figure it out.
Okay bro, show me an amp that's clipping under its RMS voltage for a given ohm value and I'll show you a piece of shit amp. There's overhead before clip, but that doesn't mean it's rated for it. If you want to actually find the exact line of clip sure you'll want an o-scope, I just want to run my amps within their ratings and instruct others to do the same. I didn't know it would offend you so deeply if I didn't include a contrarian clause.
It's the limitation of what someone would want to set it at to avoid clipping and cooking the amp, so you can take your own advice.
