Re: low notes on Tenor sax
There are a lot of different things that you can do, but it's a bit of a trial and error thing. You can always argue that there could be a leak or do some kind of equipment change, but really practicing and figuring out what's comfortable for you is the trick. Assuming you're playing on a good horn that's leak free, with a good mouthpiece and a good matched reed... it's just practice.
Subtoning can work, and often times it's a more desirable sound over just blasting those low notes.
Try practicing, try different changes to your embouchure, and figure out what works best for you. There's no surefire way afterall!