usually as you get older, your ears get more mature and you dont want to hear really deep earth shattering bass. Sq is a term used for sound quality, which measn it hits hard, and sound quality pretty much says it all...
its not about what is good or what is bad. it is about preference. if you could care less about how the system sounds and just how many things you can vibrate than spl is for you. if you want some decent volume but are more concerned with bass accuracy then SQ is what you want. SQL is where accuracy and volume are both sought for.
nobody said you can't reach damaging levels of SPL with a SQ system.. but systems designed for sound quality are first and foremost made to sound live, accurate, and realistic, like actually being at a live performance. People who have systems for the love of music and not to impress people 3 blocks away focus on SQ.
SPL oriented vehicles are for competitions where points are awarded for the loudest vehicle on an RTA and mic. The loudest vehicle wins, so people find ways to make the cars as loud as possible without as much attention to how the music actually sounds. Some of the loudest vehicles in the world of car audio really aren't drivable, or capable of being used to play music. They're strictly used for "burping" to achieve scores approaching the 180dB mark for about ten seconds.
There are systems now that are a hybrid of loudness and SQ, known as SQL vehicles, too. These are systems designed to get as loud as they can while still maintaining an accurate soundstage and response.
Let me paint the picture even more so with sq designed systems .....Its like waking up on a beautifull morning watching the sun rise over the horizon. While the air is calm and clear and all you hear is the quiet chattering of the birds in the trees and listening to their sweet sounds and taking in the beauty of the creation around you. This is how a true sq minded sytsem really is peacefull beautifull and creative just as the creator designed it to be. Its where the creator and the listener are in harmony with one another.
