Usually, you'll be installing a 4-channel amplifier with speaker-level inputs. The best way to connect it to a factory system is to tap into the stereo's speaker outputs for the amp's input signal. Then send the amp's outputs back to the stereo's harness, and on to the speakers through the factory wiring.
Get some 12 AWG speaker wire and you'll be fine for your 12V wiring. This assumes that you are not running very long lengths of wire. 12 AWG is roughly 1.6 ohms per 1000', and you want to draw 7A, so at 1000' you'd be dropping 11.2V in your wiring.
In almost all situations therefore, biamping with similar amps will result in better sound quality than bridging. Bridging is best left to professional sound-reinforcement applications, where sound quality is secondary.
So 45 watts into a 90db speaker is as loud as 4.5 watts into 100db speaker. The speaker sensitivity matters a LOT and they vary over about two orders of magnitude (85db to 105db roughly.) In a huge room, or with less sensitive speakers, or if you want to go deaf, you might need more than 45 watts.
Your amplifier may have just overheated. Some amps will go into protect mode if they get too hot, which can prevent a more permanent failure. The most common cause of overheating is a lack of airflow. If your amp is located underneath the seats, or in another confined space, that may cause it to overheat.
There are two ways to wire four speakers to a two channel amplifier: in series or in parallel. Amplifiers have both a minimum and a maximum level of impedance and it is important to stay within these limits. As many speakers as your amplifier can handle can be wired together.
Due to the total impedance, it is rare you can wire more than 2 speakers in parallel. If each speaker is the same impedance, it is easy to calculate the total load impedance of speakers in parallel. Simply divide the individual speaker impedance by the number of speakers.
average probobly 5 to 10 amps. crank it high 'till you hear distortion and you'll be making 8 - 12. By then your car stereo will shutdown or die if not the speakers that gave in first.
In other words, when exposed to the same amount of power, a 1 ohm speaker may blow out easily, while a 4 ohm speaker can take the load effortlessly.
is it ok to use my 1 remote wire for both my amps? Yes, you can do this. It will not be a problem. Run the remote turn-on from the head unit (usually the blue wire) to amp1's remote turn-on connection, then run a wire directly from amp1's turn-on connection to amp2's turn-on connection.
A1: No, there isn't any trick to wiring two amps to one capacitor. Here's how you'd wire it all up. This fuse is to protect the main power wire (and your vehicle in case of a direct short). Connect the other end of this main power wire to the positive terminal of your capacitor.
