I assume from your setup that you are playing classical tenor.  

1.  The very first thing I would do is to make sure there are no leaks.  Even small leaks in the right locations can reduce volume.

2.  If there are no leaks, the cheapest adjustment is to try a few different brands and strengths of reeds to look for one with more response.

3.  The Selmer D does have some back pressure, so you might want to experiment with mouthpieces that blow a bit more freely, and then realize that it may impact your embouchure in order to maintain the tone you like.

If you take lessons, I would discuss reed and mouthpiece options with your instructor.

Good luck!

 

You have a very lucky family if you are being told you aren’t playing loud enough.  My family has banished me to practicing in the basement.

I have a few other thoughts - as it is not altogether common for a sax player to be told they are not playing loud enough.

Please also consider an alternative possibility.  If you are receiving this instruction from a conductor, during ensemble practice, the problem may be that the instruments around you are playing too loudly, and that their might need to be a second sax (assuming you are alto) sitting next to you.  Sometimes it is easier for a conductor to ask one person to play differently, than to tell a entire section that their dynamics are way off.  Consider recruiting another sax to the ensemble.  You may be playing just fine....

When I talk to my brass friends, they always say that the last thing they want is a loud sax.

Performance anxiety normally wrecks my tone, but not my volume so much.  I’m sure it impacts different people differently.  My son vomits.