Hi,
I really want to keep my stock HU, and only adding
Powered Subwoofer (or Sub + Power combo).
So I need to get the Audio Signal input from stock HU speaker line level (ie. rear speaker cables).

What I want to know is, did 2013 Honda Sport Stock HU (non Navi),
have a "EQ" that rolled down the low frequency signal (especially at high volume level) to prevent the stock door speaker from distortion?

Because if the stock HU rolled down the low freq signal, that mean the added subwoofer will not get the "FULL" low freq input...

ok, I make it more simple, did the stock HU line level speaker out have the Full FLAT 20hz to 20khz output or they rolled down the dB at the lower frequency range (ie. below 80hz).

Please kindly help me with this question.
Thank You.