This topic is for all the 2011 and up people who have installed aftermarket subwoofers in their vehicle AND are still using the factory head unit. I'm not certain if this will apply to those with the Sony system who have up-sized the subwoofer.
So while doing research for an upgrade of my own, I ran the output of the factory head unit directly into an RTA as shown in this post
. It's clear there's a high-pass filter built into the factory head unit's output. With factory audio, I couldn't really tell as reproduction of frequencies that low with the small factory gear ain't happening regardless. I wasn't sure at the time if this would be audible/bother me with aftermarket gear installed. Well now that I've got it......HECK YES IT IS.
To all of you affected by this, here's a test. Using your phone connected to the factory head unit, listen to a song with some deep low bass, or heck, even a bass sweep. Now unplug the RCA input from your amplifier, connect your iPod/phone to a RCA-3.5mm adapter cable and plug that into the amplifier. Play the same track and listen again. You may need to adjust gains up or down as the input signal strength has changed, but output level IS NOT
what we're listening for here. We're listening for deep low frequencies that weren't present when using the factory head unit as the source. I promise you that your subwoofer will pound like never before.
So how do you fix this?
1)A bass restoration piece like the Audiocontrol Epicenter or any digital based one such as the Fosgate 3sixty, anything Kicker Shocwave, or one of the like 3 JL processors. The quick and dirty of how these work....they read the bass frequencies input, allow it to pass through and also divide those frequencies in half and output that result also. They all claim to read surrounding harmonics to make it sound natural.
2)An aftermarket head unit.
Post up any questions you have or any results you get from my above test.