Here's a whitepaper about the response-smoothing benefits of multiple subs (from a sub manufacturer, yes, but multi-sub measurements from many independent enthusiasts also support the findings in the paper):
Originally Posted by ComputerTech0903
Ughh thx level is 85 decibels with 20 decibel peaks not 100 decibels and 20 decibels for peaks.
Here's a thread about reference level. As you said, it is 85db with +20db peaks for the speakers, except for the sub (LFE channel), which is +30db (115db):
Note that "reference level" is just a specific volume level, which requires enough headroom to handle the peaks (whose maximum level is determined by the recording format, e.g. Dolby Digital, or DTS). But of course, people actually listen at levels that differ from reference level. Most people watch TV or movies well below reference level. But it is fun to turn it up to reference level, or higher, sometimes, and you can do so without damaging your hearing so long as you limit the exposure time appropriately for the level that you choose.
Building a system that can play at reference level is non-trivial. It is not easy to hit 115db at 20Hz at your listening position, for instance. It takes multiple subs, which is an additional reason, beyond the response smoothing reasons that I already mentioned, why someone might want multiple subs. Very few home systems can hit reference level, and most of the ones that can were probably built with a specific focus on being able to do so. I think we got on this particular tangent because you were skeptical that having subwoofers that can play to 120db has any value. For many people, it probably doesn't. But you can make full use of subwoofers that can play 120db or more at your listening position without immediately damaging your hearing. For a lot of us, achieving that kind of audio performance is a hobby, and experiencing it is a thrill.
You don't have to participate in the hobby, but I assume that you came here to learn about this stuff. You asked us why people have multiple subs, and why anyone wants to run their bass "hot". Several people including me have given you reasons why. Unless you are BassThatHz's neighbor*, I don't think there's any reason to be mad. Let's keep this friendly -- we'll have a better discussion that way.
* I know, BassThatHz, that you are taking extraordinary measures to create a sound cocoon to maximize performance and minimize neighbor disturbance -- I was just kidding about that neighbor thing.