I have a 2016 EX-T which is the same, I am also running Honda Hack and viper4android to get ride of the stock bass roll off in our system. I just rewired my audiocontrol DM-608 DSP to take high level inputs instead of RCA inputs. We do not have an amp and you need to tap outputs from the radio...
If you are going aftermarket speakers and amplifier you will need a DSP for summing all the channels bit if you want just a flat signal with no bass roll off you can hondahack your headunit and install Viper4Android
you can go to a harbor freight or something and buy a multimeter, they cheap
Oscilloscope would be best so you know when you are clipping and if your signal is clean
also you may want to set you cross overs too
Maybe you should of gone with a dual 4 ohm sub (wire to 2ohm)or single 2 ohm sub so you can get more bass, cause I think your speakers might over power your subs
Do you have an oscilloscope or multi meter to tune the gains for the amp?
its ok with just the Viper but I got the Audiocontrol DM-608 for better tuning, the DM-608 does sound alot better though, but the Viper does remove the bass roll off
you will need an amp and sub if you want to us the audiocontrol lc2i
the lc2i is an active line out put converter it is not an amp and it cannot power anything
What amp are you trying to install? if its just a subwoofer amp you can use you a line out converter and tap the rear speakers but if you are installing a multichannel amp you need to tap the source from behind the head unit with some line out converter
this happened to me once when i installed new speakers on my civic, it was because of a loose connection on one of the speakers, sometimes hitting the speaker area would get the speaker going again but i just rechecked the connections and it worked
Our stock head units have Bass Roll off so after a certain point the bass does not increase when the volume does, setting gains wont really help and yes an AudioControl LC2i with ACCUBASS will help.
Do you have the 7 inche touch screen? if so you can get hondahack and get android viper4android...