The most common hearing impairment is high frequency loss - can't hear the high notes so consonants like "d", "p" and "t" become indistinct. The sibilants are lost.This problem gets worse with age.
You say you can't hear "the lower speech tones". Do you mean you cannot hear the lower frequencies of the human voice or you cannot hear speech when the volume is too low?
I suspect the latter, and I suspect you need treble lift (boost) not mid-band lift.
Listening to radio on Medium or Long Wave is to be avoided as the high frequencies are poor. FM is much better but you need a radio with a decent speaker to spit the words out.
Best of all listen on decent headphones or earbuds.
As for a radio with a graphic equaliser - there used to be many "Ghetto Blasters" on the market that had them - now whether they can deliver audio clean enough for you to find intelligible is another matter.