4 channel amp phasing and gains trouble

[ACDCfn]

Warning, long and complicated stereo phasing/gain adjust question.
Current setup:I installed alpine KTP-445U Amp in my Vaquero, it's a 4-channel amp, 45 watts per channel, that can be set to run at 4 ohms or 2 ohms via dip switches, it has two gain controls, front and rear. I've installed upgraded Alpine DB-521 4 ohm speakers in front and left stock speakers in the Harley back/tour-pack that say 2 ohms on them. After 3 days of trying I am about to give up attempting to set all speakers in phase and set proper gain levels on amp.
Phasing problem: If I plug speakers according to what my eyes and multimeter indicates (positive wire to positive post of each speaker and negative wire to negative post of each speaker) and then run a test track (http://www.audiocheck.net/audiotests_polaritycheck.php), my ears clearly indicate that speakers are actually out of phase. Even though as far as I can tell visually and according to the multimeter they are plugged in correctly. The caveat is, I am playing phasing test tracks via Bluetooth as the stereo only plays radio or Bluetooth, no cd or aux in. Not sure if that matters that I am not playing test track off a cd but I figure since all of my music comes via Bluetooth so should the test track. So to set all speakers in phase should I be trusting my own ears or the multimeter and my eyes cause I am getting contradictory results from both??!! If I set it according to my ears, multimeter shows that left side speakers (front and back) have a reverse polarity but if I plug them according to multimeter then test tracks sound out of phase.
Amp gain level problem: so I know the formula to set the gains with use of multimeter is square root of watts times ohms. First question, is it ohms of the amp or ohms of the speakers? Second question is, amp can be set to either 4ohms or 2ohms also front speakers are 4 ohms and rear are 2 ohms. Should I be setting it to 2 or 4 ohms? Also since it has two separate gain controls do I cut the result of formula in half and use that number for each gain control?
To top all of it off, all of a sudden I started getting white noise on my rear speakers. Even with gains set to minimal and volume very low still hear white noise. Did I fry the amp? It wasn't doing that before.

[gssbmm]

Have the same amp. I would double check all the working from the deck to amp. That's as helpful as I can be there. As far as the while I would check your ground. The better speaker is probably just able to play a whine that was always there. I had to move my ground to the frame and grind off some paint to get a good metal connecton and my whine went away.

[robj]

been out pf car audio for a while now but youre putting to much effort into putting speakers and amp on a bike. the rear speakers being 2 ohm will already double in power in theory being 2 vs 4 ohm. may explain the noise vers the fronts. i would make sure your ground is good and swap out the HD speakers for a decent set of 4 ohm speakers. remember 2 ohm is going to work the amp harder. harder is hotter and most ampl, especially lower end dont like to run 2/4 ohm at the same time.

as far as setting the gains there is no need for a formula. set it by ear/ set volume to max of where you want it. gain the amp up til it distorts and then back the gain off a bit.

[carpeviam]

If your ear is not the exact same distance from each speaker, then the sound will be out of phase when it reaches your ear. This is why in a home theater there is a sweet spot and most decent systems allow you to adjust the delay of the speakers (most use milliseconds, mine you enter the distance from each speaker to the chosen sweet spot). Another good example are speakers like the Bose L1 model II. Each speaker tower is a speaker array designed to provide maximum sound coverage. The design is great for using 1 speaker, but if you try to use 2 of them with the same feed, you will have noticeable phasing as you walk around the room.

[VulcanE]

been out pf car audio for a while now but youre putting to much effort into putting speakers and amp on a bike. the rear speakers being 2 ohm will already double in power in theory being 2 vs 4 ohm. may explain the noise vers the fronts. i would make sure your ground is good and swap out the HD speakers for a decent set of 4 ohm speakers. remember 2 ohm is going to work the amp harder. harder is hotter and most ampl, especially lower end dont like to run 2/4 ohm at the same time.

as far as setting the gains there is no need for a formula. set it by ear/ set volume to max of where you want it. gain the amp up til it distorts and then back the gain off a bit.

As far as "car audio" I would agree with this statement.