Whine at higher volumes
I drive an 05 ZX4 St with the sony system. I have beefed up the speakers, added bluetooth to the stock headunit, and slapped some subs in the trunk. Naturally, I like to crank my system when driving around, and I have noticed a rev whine. I have better grounded the head unit, the cigarette lighter(as that is how I power my bluetooth) and more. Yet I still have whine. any tips?