Def voltage drop if in sealed enclosures that don't afford severe loading issue nearing subsonic, combined with headlight dimming and inducing a protection fault.
Subsonic filter could be set too low for the driver's frequency range.
Bass boost frequency can be centered too low or the bass boost amplitude level is too high (i avoid using bass boost)
Both of these can cause your amp to be overdriven if you dial in your amp gain without those adjusted prior or during. This is however, if your electrical chain is sound and you have a sufficient alternator to provide the necessary amperage. If not, that is the most likely culprit.
Upgrading to a 250a alternator is just using a band-aid on a sore tally-whacker when it is required to provide additonal power for other audio equipment, vehicle accoutriments, and it's operating systems.
Adding a second alt purely for the audio system rated for the total potential amperage draw of said system, usually determined by adding up the sum of the required fusing for all equipment, is a foolproof way to keep your voltage above the threshold of amplifier overdrive. Again, this is only applicable if your 12vdc connections are sound.
I dont want to discount any other's advice, but ive never had any of my installs come back for voltage drop unless someone has been adjusting dials i tell them not to when its necessary to guarantee my work. If they cannot afford the electrical or want to pay for it, i tell them the risks and dial everything back to avoid overdriving with what they have, excluding me from culpability to the system burning up.
