07 chevy express van speakers ohms?

I am ugrading my sound system, adding my JVC KD-HDR1 head unit and replacing the factory speakers with some decent aftermarket ones. I also plan to add a 10" powered sub to be placed in the back behind the rear seat. The "rear channels" are supported by two 6x9s above the rear doors and two 4x6s just behind the middle row seats. The fronts have 6.75" speakers low in the doors, which I plan to replace with component units (mounting tweeter on the dash facing windshield for dispersion). With four speakers being driven by only two channels, can I assume that these speakers are two ohm (for a total 4 ohm load), and if so, should I replace them with 2 ohm speakers? Or is it more likely they are 4 ohm speakers giving a total 8 ohm load? Any advice on determining my best choice for replacements would be very appreciated, keeping in mind that I'm not an electrical engineer. I do have a basic test meter, so I can check resistance if necessary. Thanks for your help.Learning every day . . . .

My question is not about the front channels where I will use components. I'm wondering what speakers I should use to replace the FOUR REAR speakers. With there being four speakers on two channels, I'm guessing they might be 2 ohm speakers, and if so, should I replace them with 2 ohm speakers -- this is my question. If they are 2 ohm speakers now and I replace them with 4 ohm speakers, the db output will be dramatically reduced, which is not what I want. On the other hand, if they're now 4 ohm speakers and I replace them with 2 ohm speakers, the head unit may have trouble driving them and I'll have excessive distortion. I am assuming that the factory head unit is a four channel, rather than six channel. I'm hoping to draw on someone in the group with GM OEM component experience.Learning every day . . . .

If it is not a Bose system, I highly doubt that there are 2 ohm drivers in the vehicle.  But you are correct in assuming that if you replace 2 ohm drivers with 4 ohm drivers, you will notice a decrease in sound level.

I discovered that all four (rear and center) speakers are 8 ohm. So they must be wired such that the combination provides a 4 ohm total load at the head unit. If I replace these OEM 8 ohm speakers with 4 ohm speakers, then the head unit will see a 2 ohm load. Will my JVC handle this kind of a load without increased (audible) distortion? If so, can I add an inline resistor to increase the resistance at each speaker so that the head unit sees closer to 4 ohms? I'm sure the wiring (quite long) has some resistance to factor in, but is it significant?Learning every day . . . .

A resistor would work, but it would use up half the power being sent of the mere 17 watts rms(on a good day) the deck puts out, not a REAL option at all. You would get the same power to the speakers by running them in series at 8ohms per channel, with less work on the head unit and also no extra cost. Look for 8ohm drivers to run in parallel or 2ohm drivers in series for a 4ohm load. The rating is at 4ohm for the deck. That is the lowest recommended impedance and i would not go below it. It may work for a bit, but it is going to burn up those channels of the head unit.

Thanks for the suggestions. I already looked for 8 ohmm speakers and they are incredibly expensive. The series wiring method with 2 ohm speakers makes the most sense to me. The other alternative is to disconnect the center speakers, which don't really do much other than send music to the back seat (where there will rarely be anyone sitting). At this point I'm thinking this may be the best (and easiest) solution.Learning every day . . . .

Another thought -- I chatted with a Crutchfield rep last night, and he indicated that other customers have replaced 8 ohm speakers with 4 ohm speakers using an aftermarket head unit with good results. His reasoning is that the factory wiring is small gauge, which provides additional resistance, such that the amp sees something closer to 4 ohms than if heavier gauge wire is used. In my case with the full sized van, the wire lengths are pretty extreme. Does he have a valid point?Learning every day . . . .