Adding 5 channel amp + apline speakers + rockfordfosgate 12 inch sub

Hey everyone, so im looking to upgrade my 2017 tundra non-jbl crewmax's sound system and I just wanted to ask some questions because I can't seem to get any straight answers just googling around. I installed Alpine S2-S69C and S2-S65C in the front and rear doors with some sound deadening from Amazon, but they honestly sound worse than stock, and so after doing some research, I learned I need to upgrade the amp and I decided I want to add a sub. I bought an NVX 5 channel amp, a Rockfordfosgate 12 inch shallow sub, and a ********* amp converter so that I can replace the stock amp. Am I missing anything here? Ive read about DSP's but I'm not sure why I would need one. Also, I installed carplay into the stock HU with an aftermarket box because I really like the stock look so I'm not looking to get a new HU.

Is there anything else I need to get the system complete?
Does the stock HU send the complete sound frequency out to the current amp? Or does the stock HU have a built in filter before it sends out to the amp?
Also, since the NVX amp is 5 channels, will that 5th channel going out to the sub get the right frequency? or will it be wrong if the stock HU doesn't send frequencies that low to the amp?

Thanks for any input!

 

If you can return the TT "Amp converter" I would. They are pretty bad, hence why their name turns into ******* (they've been banned from here). If you can't return it you could give it a try.

An audio control lc7i should work well for you. There are a few threads on this site using them. Look up the pinned threads on the audio section

Other than some wiring, you should be good

 

With the stock head unit, theres some factory EQ/signal processing going on. Reason people use DSP's is to correct factory signals, or in high end builds to super fine tune each speaker in the system for things like frequencies, time delay etc. You do not need a DSP and most amps nowadays accept high level inputs which negates the need for a line output converter as well, however a lot of folks use the Audiocontrol line output converters like @Danimal86 mentioned because they have a feature called Accubass which restores some of the factory signal. They also allow you to have as few as one input, say your front door, and you can have that input signal copied to multiple output channels, or you can have separate inputs and outputs for each channel. For a 5 channel amp, it's nice because you don't need a dedicated sub input:


As far as factory frequencies go, I don't know that anyone's tested/recorded the system with a mic, but lots of people leave teh stock head unit in place and add subs with great success. The system should have frequencies low enough for a sub, and then the AccuBass feature will improve them as well.

Another option would be if your NVX amp accepts high level inputs, you could have your factory signal wires go straight to it for input on the 4 channels, and then put a Kicker Keyloc which does auto-DSP in front of the subwoofer channel to really be certain you've got a good sub channel. I just installed a Keyloc in my wife's car that has Bose, after having tried an Audiocontrol LCi, and I was much happier with the Keyloc but again many people on here report success with the LC7i.