Inverted Speaker Install

https://www.the12volt.com/installbay/search.asp?KW=inverted&SM=1&SI=PT&FM=2&OB=1&Submit=Start+Search

There is some good information here.

1. The only thing that is crucial about reversing phase with inverted speakers is this:  in a setup where some subs are inverted and some are normal, the inverted subs have to have the polarity reversed to be in phase with the normal subs.

In a setup like yours where all subs are inverted, reversing polarity becomes a matter of what sounds best in your normal listening position.  The simplest way to wire them is the normal way as shown in the wiring diagram.  The polarity can be reversed by switching speaker wires at the amp, or using the amp's 180 switch.  Try both ways and pick the way that sounds best to you while also playing the speakers in the rest of the system.

2.  Sound quality should be just as good as if all three were normal.  Make sure you take into consideration the difference in air volume in the enclosure, though.  The inverted sub will not be taking up space inside the box, and in fact will add to the space a bit with the air inside the cone area.  The example below illustrates that, with the gray area representing the air inside the box:

The above were part of two of my posts in the threads listed in the search.  Both apply to your situation.  1.  Using only one sub, no change in sub wiring is needed, as the post above explains.  2.  Be sure to account for air volume... and 3.  As you have seen in some of the threads, there will be no difference in sound quality or output if everything is set up properly.

You can connect as many speakers as you want to a one-channel amp, as long as the total impedance is okay for the amp to handle.  Inverting a sub doesn't change the impedance.  But it changes the way the sub will produce sound.  Instead of producing the sound waves (that you hear) from the front, an inverted sub produces those sound waves from the back.

Sound waves are produced from both the front and back anyway.  One side is in the box, the other side faces out.  Whatever side is facing out is the side that you hear sound from.

If you have only one sub, and you invert it, you don't have to wire it any differently than what it shows in the wiring diagram.  Polarity can be reversed by switching the pos and neg wires at the amp terminals, if it sounds best to do that.  However, if you have two subs, one is normal and one is reversed.....one of the woofers has to have its wiring in reverse, too.  That's typically done on the inverted sub, although it doesn't make any difference which one's wiring is reversed.  They just can't be identically wired. 

Reason is, most amps made for subs have a 180 degree switch...because there are installations where the phase at 180 degrees sounds better to you in the driver's seat than when it's switched to 0 degrees.  (180 degrees is the result of switching pos and neg wires, too.) It has to do with how the sound waves interact with the vehicle before they reach your ears.  So, the wiring can be normal on the inverted sub and reversed on the normal sub, or vise versa.  You listen to the results while playing the whole system, and change polarity either with the switch or by crisscrossing the wires at the amp, until you're satisfied that one way sounds better than the other.  That's normal whether you invert subs or not.

Multiple subs on a mono amp........> fine.  Be aware of impedance.

Multiple subs on a mono amp, some inverted.........> fine.  Be aware of impedance.

Multiple subs, some inverted.......> reverse wiring polarity on the inverted subs so they all thrust outward at the same time (outward meaning not into the enclosure).