Sound Quality of Direct TV audio

I recently put a 1/3 octave spectrum analyzer on my Direct TV audio outputs and was shocked to find that they are brick wall filtering all low frequencies below about 150 Hz. Not a gentle roll off mind you, everything from 150 Hz down is gone.

I thought they were supposed to be delivery "high quality" audio. Anyone else discover this or am I getting something unusual?
"11-02-15: Philjolet
the current DirecTV does not use RCA outputs at all, only digital"

That's not true. It depends on what receiver you buy. Also, if there were no analog outputs, how was the OP able to take his measurements?
Our DirecTV HD DVR HR44-200 connects to an Oppo 105D via HDMI that in turn connects to a Bryston SP3 via HDMI. Program material often lights up subs crossed at 40 Hz mains and 80 Hz center and surrounds.

"11-03-15: Philjolet
Zd542 I presumed he had an older unit"

It doesn't matter. They still put analog outputs on current model receivers. I don't know if they do it with every one, but you can still get them.