Q. When one reads Krias Shema and extends the word Echa’ad as required, does he say the elongated alef letter (Sefardi pronunciation) together with the ‘chet’ or just by itself. I have heard in shul both customs. Which is correct?
A. Shulchan Aruch (O.H. 61: 6) rules that one should extend on the ‘ches’ enough to think that Hashem rules on the heavens above and on the earth bellow. Then on the ‘daled’ he should stretch out enough to think that Hashem rules on the four corners of the universe. Mishna Berura (61: 18) quotes Magen Avrohom that the ratio of elongation is one third to two thirds.
He further explains that extending too much will create mispronunciation in both cases, including the sound of an ‘o’ without the ‘ches.’
Horav Shlomo Miller’s Shlit’a opinion is that extending the ‘daled’ should be done carefully, without adding any extra vowels sound to it, just the plain repetitive ‘D’ sound.
Rabbi A. Bartfeld as advised by Horav Shlomo Miller and Horav Aharon Miller Shlit’a