What is the difference between pronouncing light letters like laam with a dammah and heavy letters with a dammah

Question
Assalaamu alaykum

May Allah accept your efforts to educate the ummah. I have a question about the dammah. What is the difference between pronouncing light letters like laam with a dammah and heavy letters with a dammah, since both require rounding of the lips. Another example is the seen and the saad with a dammah on them, what is the difference.

Jazak Allahu Khayran for all your help

Answer
Wa alaikum assalaam wa rahmatullahi wa barakatuh,
The dhammah is the same for letters of tafkheem and letters of tarqeeq as far as the mechanism of the dhammah.  The difference in the sound is only the difference between the raising up of the tongue and focusing of the sound to the roof of the mouth for the tafkheem letters and the absence of raising the tongue and the sound going out the mouth for tarqeeq.  For both tafkheem and tarqeeq there is a circling of the lips of the same type for a dhammah.
Wa iyyaakum