It won't burst into flames and explode if you run the "normal" Qts driver in a sealed enclosure, but the "normal" Qts drivers really don't have the parameters to excel in sealed enclosure performance.....the parameters are really more geared a little more towards ported enclosures. I don't know exactly how high the High Qts option actually raises the Qts, but if your intention is to run them in sealed enclosure, I'd probably recommend it since they specifically offer it as an option for that purpose and with it's "stock" parameters, it's not as ideally suited for sealed enclosures. If you were going to simply use them in a sealed enclosure for a period of time but plan to use them more permanently in a ported enclosure, then you would be okay using the normal driver in a sealed enclosure.