Wiring 6 speakers to 4 channel amp-how to handle fade control

Willhound

Going to be installing a new stereo head unit, amp and 4 new speakers in the cockpit, retaining the original two speakers in the cabin/bow.
The head unit puts out 60W RMS per channel at 4 Ohm's and the amp, 100. But this is kind of irrelevant.
The amp is four channel (2 front, 2 rear) and I'd like to use that to drive the four cockpit speakers where I want more volume for listening at cruising speeds. I'd wire the two cabin speakers off the head unit.
What I didn't think about when buying the amp is that there are often times when I want to stay up late and listen to tunes above deck while the Admiral heads below. The only way I can think of accomplishing this is to run the two cabin speakers off the front channels of the head unit, the two forward cockpit speakers off the rear channels of the amp and the two rear cockpit speakers off the front channels of the amp. This way I should be able to use the fader control on the head unit to shut down the front channels and therefore the cabin speakers, while keeping the rear channels playing (which will actually be the two forward speakers nearer the helm).
Sound right? Any other way of accomplishing this? I had also thought about just placing a speaker switch between the head unit and cabin speakers so I can just switch them off and play all four speakers above deck. Maybe this is the better way to go?

Stodge

My stereo is set up so the fade has the inside cabin speakers as "front" and the amp for the 6 cockpit speakers as "rear".  I believe this was from the factory.

Willhound

That's how my current factory set up is. I'm assuming the accomplished this by running the cockpit speakers in parallel but I don't want to do that and split the amp output. My new head unit only has 4 RCA outputs to hook to the amp, 2 front and 2 rear and then the regular speaker output harness, again front and rear. More I think about it, maybe just a small set of toggle switches to cut out the two cabin speakers, or an A/B switch box and just use one side.

Stodge

I was a little concerned at first but the amp seems ok with the 6 speaker set up.  But you've given me an idea.  I might look at a speaker switch to have the TV play over the cabin speakers.  Need to look at inputs on the stereo too.  

Thanks @Willhound now I have another project to figure out. 

skennelly

@Willhound - If you go the switch your biggest issue will be the added resistance an inline switch will add increasing the overall impedance.  That can eventually destroy your head unit.

Definitely use a proper speaker switch if you go the switch route as those have the internals to handle the impedance changes ect...

Willhound

  Happy I made you think.. you can easily do that with an A/V switch box with RCA inputs/outputs. Made me remember, I have one in the basement someplace. I could splice RCA plugs to the speaker wire and use it to switch the speakers. I wonder about it adding impedance to the channel....
EDIT.. @skennelly your post just beat mine....duly noted!

Cableguy Greg

The easiest way to connect your 4 channel amp is to leave the "front" speakers connected to the "front" channel on the head unit. For the cockpit, use the "rear" line level out to the line level in of the amp. Since the amp is a 4 channel amp and the original amp was a 2 channel amp, you need to place an RCA splitter before the amp. It is a dongle with 1 female and 2 males on it. You will need 2 of them to get you 4 channels. Then connect the individual speakers to the 4 speaker outputs on the amp.

https://www.amazon.com/InstallerParts-Splitter-Compatible-Most-Audio-Systems/dp/B008NCD5WC/ref=pd_lpo_vtph_107_lp_t_3?_encoding=UTF8&psc=1&refRID=857RZGMASHAZH93SJKXC

Willhound

@Cableguy Greg that works! So just take rear channel feeds off head unit and run into both the "front" and "rear" inputs on amp, correct? That way I get full watts to each speaker and the fade control on the head unit acts as control. I like it.

Cableguy Greg

Willhound said:

@Cableguy Greg that works! So just take rear channel feeds off head unit and run into both the "front" and "rear" inputs on amp, correct? That way I get full watts to each speaker and the fade control on the head unit acts as control. I like it.

That's correct. The front and the rear on the amp are connected via the Y cable.

LaRea

Typically, the radar arch speakers would be wired to the amp's "front" outputs.  The four other speakers would be wired in parallel to the amp's "rear" outputs (and would be slightly quieter than the arch speakers).  

J3ff

I don't even have an amp, I just wired the 4 top side speakers right to the rear radio output and the inside ones to the front 2 speakers.. 

If you are moving at 30+ and try to blast the speakers to something so loud you can hear it clearly it does start to break up...but I don't usually do that..instead just have it playing at anchor.