Alright I have a few questions about this setup. Just installed the 6.5" alpine spx-17ref speakers and tweeters running to crossover, and powered by an alpine mrp-f300 amp. I used 2 twisted rca cables for input to the amp, and output going straight to the crossovers, but don't know whether I should bridge the outputs or not.
I set the 6.5" speakers and tweeters to run active to the crossover, and have messed around with it using 2 channels, and also tried by bridging the output. Is this the same thing, or does it mean I'm only using half of the amp's power? I thought it sounded better without bridging, and I definitely have more than enough power. Anyone have some input on a similar setup?
I am running the amp in full range so I can't even control the amp's crossover, and the only advantage I can think of is maybe the ability to control both of the gains if I bridged it. I have the single gain almost all the way down now, and it sounds amazing.
I don't have the rear speakers plugged in, but I guess I could buy some nicer coax speakers for the rear and run them to the amp, but don't know if it would make much of a difference. Any suggestions?

 

A typical push pull output power of an amp is determined by its rail voltage which is the supply voltage to an amp. Without a dc-dc converter it would be limited to about 12 watts or so for a single channel based on battery voltage of 13.8 and a 2 ohm load. The formula would be:

Voltage = System Voltage / 2 times sqr root of 2

So you have 13.8 / 2.828 = 4.88

Power = Voltage sqr / resistance

So you have 23.8144 / 2 ohms = 11.9072 watts

In this setup the system voltage determines the maximum output for a 'full cycle'.

If you took two push pull outputs and bridge them (commonly referred to as a 'H' configuration of push pull stages) the system voltage determines the maximum output of each 'half cycle'. Since the power output is determined by the sqr of the system voltage doubling the voltage using a bridge setup could increase the power by up to 4 times assuming the load impedance was the same (which is often not the case). In this case a non dc-dc converter amp would yield about 47.6288 watts at 2 ohms. However in many cases the real stable output would be half of this using a load of 4 ohms.

To keep from being limited by the battery voltage amps employ dc-dc converters to raise the rail voltage. Another advantage is since this new voltage output is usually well regulated you will not hear blooming (volume increases) with changes in system voltages as you would typically encounter in a car.

So basically bridging has the potential to increase your output by up to 4 times but often times you will see it listed as half this amount based on a load impedance of double what the rating may be not bridged.

For your amp:

75 watts x 4 channels at 2 ohms

150 watts x 2 channels at 4 ohms

It is rated for a minimum impedance of 2 ohms (not bridged) and a minimum impedance of 4 ohms (bridged). You may see this stated as 'stable at 2 ohms'. Follow the manufactures ratings or you can actually damage the amp. As you can see very tolerant not bridged, not so tolerant bridged.

You should be able to determine to a certain extent what is in the box by counting the number of power transistors. A push pull single stage would normally be 2 transistors so a 4 channel amp would have 8. Now if this is the case you can figure out the all important rail voltage based on rated peak output.

Note this all assumes theoretical values, you can expect much less in the real world, possibly only 50-70% for a Class A or AB amp. As much as maybe 90% for a class D amp (typical subwoofer). I believe yours is a Class AB (typical full range amp). This will then give you the wire gauge to use.

 

Wait...what? Haha, forgot to mention that I wasn't an EE major, so most of that is way over my head. From what I did gather is that I should make sure the speakers are running at their suggested ohm range. The component set is 4 ohm, and I have it powered at 4 ohm since I have it set up with one channel going to each, right?

On another note, I have tweaked the settings and added an additional 10" sub in the trunk. At first it was way too much bass, as I expected it to be. But after tweaking that some I have the gain almost all the way down, running at a low frequency setting, with 60db crossover.

With the tweets and 6.5" subs up front, and the addition of the 10" MTX in the trunk, my system finally sounds how I imagined it. It was a PIA to run speaker wires through the doors and into the trunk, but it was definitely worth it.

Thanks P for trying to help me understand this a little. I appreciate it.