RCA Voltages, Y Cables, And Amp Hookups

I'm trying to figure out the best way of doing this, and trying to understand exactly how everything works out. Going to post this in a few places, so you may be seeing this more than once. :)

I've got 4v preouts on my Alpine source unit. I have two Type R 10" woofers and two 600w Alpine monoblock amps, where the max (or min) gain setting is 4v.

The stereo outputs on the source unit I currently have going to one amplifier, where two RCA Y cables split those into the first amp and into another set of RCAs going to the second amp. Now if there are 4 volts coming from the source, going to the first amp and to the second amp, is each amp still getting 4 volts and just less current? Is each amp now getting 2 volts? Should my gains still be set for 4 volts, or should I turn them down (up) to 2 volts? Or maybe somewhere in between?

Is there a better way of setting up two amps like that? I don't really like the idea of using Y cables, but I wasn't really sure of another way to do it. The amp doesn't have a passthrough so that isn't an option.

Here's the amp I have two of:

https://www.crutchfield.com/S-2NiPePwXtbS/cgi-bin/ProdView.asp?search=M650&i=500MRPM650

And here is an awesome diagram of what I'm talking about:



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2000 BMW 540i 6 speed

A y-splitter sends the SAME signal and voltage to two sources.  No need to worry that the voltage is being halved, or that the signal is weakened.

A better way of getting signal from one amp to another is via the passthru in amp #1.  Less wiring and connections.  But if neither amp has the passthru feature, use the y cables.  Better yet, use the sub out preout to the sub amp with dedicated cables, and the preout to the mains amp with its own cables.

Setting gains with multiple amps is by the book basics:  first set the deck output at its highest clean level by playing a 0db sine wave test tone and listening for the beginning of clipping through the main speakers.  Slightly touch the volume back down until the sound is pure again.  Once that level is established, make a serious mental note of what that volume number is because it will be absolutely the highest level you will ever turn the volume on that deck.  Use the test tones and set gains on one amp and then the other, listening for the beginning stages of clipping through the amps' respective speakers.  The gains are set to match the head unit output when you're all done.  Don't worry about the deck's preout voltage ratings or the input voltage markings on the amp.

Test tones:  use a tone somewhere in the range of 400 Hz to 1000 Hz for the mids/highs;  a tone about 50 Hz for the sub bass.

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

What do you set the amp at before you turn the  HU up?    Do set all the settings at zero before you start?

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I'm on a mission to be as loud as i wanna be.

Yes, gains on the amps are turned all the way down.  Listen to the speakers through the normal wiring setup while finding highest level of the deck.

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Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.