Well they should do the trick.
Not trying to be presumptuous but I don't know your past so I mean no disprespect when I ask, that you've heard or been taught the difference between daaahh (low tongue placement, lower tones, more air) and eeeehhh (higher tongue placement, higher velocity air stream and less air)?
Try speaking these in long tones and notice how your tongue and jaw adjust. Then try playing them in an interval, say low C to E. daaaahh, eeehh, dahhh, eeeehh slowly.
Over pronounce them a little to make the muscle memory kick in. It's such a simple sounding excercise, but actually takes a lot of practise to do properly. Probably 99% of horn players don't bother doing it long enough. Look at it kind've like the Karate Kid "wax on" wax off" technique.