A simple passive speaker switcher would do the trick. More complex would be a DSP with presets.

Amazon.com: Pyle 4-Zone Speaker Switch Selector - Premium Distribution Box with A/B/C/D Switches for Multi-Channel High-Powered Stereo Amp - Supports 4 Pairs of Speakers - PSS4 : Electronics

Amazon.com: Pyle 4-Zone Speaker Switch Selector - Premium Distribution Box with A/B/C/D Switches for Multi-Channel High-Powered Stereo Amp - Supports 4 Pairs of Speakers - PSS4 : Electronics

www.amazon.com

 

That looks like a great option. Thank you!

 

Will the speakers be amplified? If so, perhaps you can run the remote wires through a relay switch to cut off the signal to the amp.

 

I hadn't thought about amplified speakers vs. non-amplified. It sounds like I should research that. I have little to no experience doing any "system" design stuff. I have a bunch of experience doing the easy, regular old head unit wiring to four speaker installations. I'm scratching my head on the impedance, watts, amp ratings stuff that will make the whole thing work as it should.
Thanks for your response!

 

What are you using to play music? Most source units (like a single or double din head unit) have at least Front and Rear. You can simply connect the inside speakers to Front, the outside speakers to Rear, and use the fader to control which set you want on. No need to buy anything extra or over complicate things.

 

Right now I don't have anything to play the music. The nice thing is I don't have to rig anything to make it work. I can still pick all the components. I understand your fading idea. There will be four speakers inside. I didn't think there would be enough power to properly wire two speakers to each of the forward speaker channels. I am I wrong? Also, I know that some head units don't send the exact same signal to the rear as they do to the front. I was thinking the sound might be a little "off" if where I'm listen is missing the other 2 channels. Maybe I'm over-thinking it?

 

It all depends on how loud you’re trying to get. You can run:

• Just a HU
• HU + 4-channel amp
• HU + 6 channel amp.

You can even just plug your phone, or music source, directly into a 2-channel (or 4-channel bridged) amplifier, then into the speaker switcher that @Stycker listed, then out to all your speakers. Just note that the minimum speaker impedance load for that device is 8 ohms.

Front and Rear signal is usually the same from any stereo source unit.

 

As others have said, fader would be just fine for speakers, and you could either go 8Ω speakers for the interior on the front channel, wired in series, and then two speakers outside on the rear channel. This would keep the stereo happy with 4Ω load on all 4 channels. This would be the easiest way and the cheapest way, using the power from the head unit (usually around 50w/channel@4channels).

If you need more volume, or need to balance the 4 speakers inside, you'll probably want to run an amp that has some sort of controller where you can choose your outputs from said controller. This would be much more expensive as you'll need a 6 or more channel amp that has some sort of dsp to control where the audio flows out to for speakers, much like @Stycker suggested.

If the volume is good, but you still need to adjust front to rear inside, you could run the head unit as normal, 4 speakers @ 4Ω, then have a small 2 channel amp for outside speakers that you can just have a switch to feed the remote turn on wire power when you want outdoor speakers on. Problem with this is that the inside speakers will be on all the time and volume will be adjusted equally for all 6 speakers.

There is one other option, and that's to look at the stereos made specifically for the RV industry. They already have a built-in speaker switch set, and many of them are set up for 6 and 8 speaker sets directly from the head unit. They aren't fantastic head units, but they are capable of exactly what you want to do with not drama or weird wiring or extra components.

 

Kinda need to know HOW you are going to use it. I had a Yamaha home power amp that could run 3 sets of speakers by using a b and c push buttons. That would allow you to run any combination.