How to Pronounce TH after N or Z American English

I recently got an email from someone

asking me to clarify a few points on

pronunciation specifically some

consonants followed by th such as s and

n this person says because their

position in the mouth is so different

from that of the th sometimes I find it

difficult to shift from one to the other

for example can you return them where is

the car also do you pronounce the th at

all times or are there exceptions like

when you talk fast because sometimes

when an American is talking I hear a th

sound but I don’t actually see the

tongue go through the teeth this is a

great question and thank you for your

email let’s start with the first sample

you gave and that is an N followed by a

th in the sample sentence can you return

them now in this case the th of them is

voiced so make sure that you’re

continuing to make noise with your vocal

cords so how does the tongue move can

you return them the tongue to make the N

has the position of this part of the

tongue raising and touching the roof of

the mouth about here hmm

then so in order to see them through the

teeth it’s just a subtle movement of

pulling the tip from here down through

the teeth can you return them can you

return them this second example where’s

the car has the voiced is followed by

the voiced th and I do notice when I say

this phrase that my tongue does not come

through my teeth where’s the car rather

the tongue presses against the teeth

this part of the tongue presses right

where the teeth come together without

actually coming through where’s the car

this would only work on a voiced sound

for the unvoiced th the tongue must come

through the difference in tongue

position between the

and consonant sound is very slight the

tongue on is behind almost closed teeth

very lightly touching or almost touching

for the th the tongue comes through the

teeth or in my case in this particular

phrase presses against the closed teeth

so the tongue the tip of the tongue just

has an extremely slight movement forward

this is the car where’s the car thanks

for your email