As I understand it, ADSL signals are passed along the twisted pair (is
that right?) telephone cables which are the same used for voice calls.
At a much higher frequency, of course. I am also under the impression
that the length of this cable is critical for service quality and
overall data rate (apart from junction / joint quality).

Would using coax for the last stretch to the subscriber's premises
provide any better quality of service?

I only ask as my cable service uses coax and I wondered about the
difference.

Cheers,

David.