Don't connect the speakers to both; connect them only to the amplifier.

How are you getting signal to the amplifier? If you're using the high-level input, you'll connect the head unit to the amplifier inputs, otherwise they will be unconnected.

Some modern OEM head units sense if a speaker is disconnected and won't work. They sell resistors to replace the speakers. Some amplifiers will have these resistors built in on their high level inputs, but not all.

Ideally the speakers you use will come with passive crossovers that include a + and a - adjustment on the tweeter level, allowing you a some adjustment. Fancier crossovers have more ways to adjust them. The ones from CDT that came with mine have 4 or 5 adjustments. If crossovers aren't available for your speaker combo, you can either try-and-swap with misc "oem" ones, or get real deep into the books and build your own. Or find an old head who did serious car audio back in the day and bribe them until you find their breaking point.

Set your amplifier gain by ear. Set the unit about 3/4 of the way up, or higher if it doesn't distort, and then adjust the gain until is really, really loud, but not distorting, and then turn down the volume. Done. Setting your gain any higher than that is pointless because you'll never listen to it that loud. Maximize the signal level at the head unit, set the gain to achieve the max volume you'll need...

 

Don't connect the speakers to both; connect them only to the amplifier.

How are you getting signal to the amplifier? If you're using the high-level input, you'll connect the head unit to the amplifier inputs, otherwise they will be unconnected.

Some modern OEM head units sense if a speaker is disconnected and won't work. They sell resistors to replace the speakers. Some amplifiers will have these resistors built in on their high level inputs, but not all.

Ideally the speakers you use will come with passive crossovers that include a + and a - adjustment on the tweeter level, allowing you a some adjustment. Fancier crossovers have more ways to adjust them. The ones from CDT that came with mine have 4 or 5 adjustments. If crossovers aren't available for your speaker combo, you can either try-and-swap with misc "oem" ones, or get real deep into the books and build your own. Or find an old head who did serious car audio back in the day and bribe them until you find their breaking point.

Set your amplifier gain by ear. Set the unit about 3/4 of the way up, or higher if it doesn't distort, and then adjust the gain until is really, really loud, but not distorting, and then turn down the volume. Done. Setting your gain any higher than that is pointless because you'll never listen to it that loud. Maximize the signal level at the head unit, set the gain to achieve the max volume you'll need...

So the only reason I was thinking to both was so that I still have control over fade and speaker level on the head unit.

I do not currently have an amplifier hooked up to the speakers in my doors or the tweeters and am currently running off of the aftermarket head units amplifier. So the 6.5s are pushing 15-20w at 8 ohms instead of 100. I’ve currently got 2 subs and my 2 Earthquake F6x9s wired and gain set properly to a safe maximum that I set through my o-scope/dmm and checking to see that I’m never pushing more than 25V constantly. I get peaks up to 30.5V but it’s okay for the subs Im running.

It’s a 2006 Honda Accord, nothing too modern and I went with a Metra head unit adapter, running a Pioneer DMH-100BT. There is a passive crossover for the Skar tweeters that I got, they’re the TWS-01. To my knowledge it is not adjustable. If it is, I would have to remove the protective wrap over the crossover, pretty sure it’s heat shrink but unsure.

I don’t enjoy setting gain by ear as I have blow several speakers using this method because they don’t have distortion, but I push the sub past its Xmech. I like to be sure that I’m never over rms and it doesn’t move excessively. I checked the head unit with my o-scope and it doesn’t distort until 35 out of 40. I gain set everything at 34 volume and typically run at 32. I always listen to it ridiculous loud, the way I have it set after trial and error multiple times is the best way I’ve ran into. I just test with multiple of my hardest pushing songs and make sure those songs don’t clip at the respective volumes I allow for those songs.

All in all, I just need to figure out how to wire the tweeters and door speakers but don’t want to try and run through the door jam through the rubber piece because I don’t know how to pull the wire through it, but I still want access to control over the system from the head unit. Thanks for the advice though. Or actually, if I have it through an rca will I still have control over fade because the amp is connected by the rcas even if I disconnect the speaker leads from the head unit?

 

Sure you could add a fuse block off of one of the outputs of the other.
If it's from a fused output your ok.
But if not you need to fuse that wire if it smaller than the original gauge of wire run from the battery.

 

Sure you could add a fuse block off of one of the outputs of the other.
If it's from a fused output your ok.
But if not you need to fuse that wire if it smaller than the original gauge of wire run from the battery.

Yeah, I ended up doing the math for it all and currently the wire sizes are correct and work together, but if I were to do that, changes would need to be made and hiding wiring will be even more of a pain.

 

But ultimately a 6 channel would be the easiest option huh

 

Dang... I just got done buying another 4 channel... lol. Alright