When finding signal to convert your OEM high level signal (otherwise known as speaker wires or your amplifiers output) to low level signal (RCA connections or your amplifiers input) it is important where this is found. Unfortunately this is commonly done incorrectly and you may be limiting the signal to your aftermarket installed system. Or worse; you're not even playing a whole range of frequencies 🤔
While some may think going to an OEM subwoofer for signal would be ideal for adding your aftermarket subwoofer and amplifier, however. In many cases that amplified signal to the OEM subwoofer is crossed over; even band passed limited to the signal that only that exact sub in its configuration is ideal for. Now, sending that 40-80hz range to your new system capable of a much wider response obviously now seems counterproductive.
More noteworthy. Shouldnt we let the new system select ita values. I mean isnt that the point of having a low pass & sub sonic crossover? So how do we choose a better location to install our converter, pre-amp or processor? Lets find out.