mix speakers?

I have an Alpine PDX-5 running the factory 2 ohm speakers in my wife's Mercedes. I have replaced the factory subwoofer though with an aftermarket Pioneer, but cannot for the life of me remember which one. We have developed a bad static problem on one of the channels (OF door...not the subwoofer) and I need to do some isolation work to see where the problem is. I get it after you hit a bump in the road. Getting inside the door panel is a real pain and I don't want to do that if I don't have to...and I don't think I will. What I want to do is just set a cheap 4 ohm speaker in the car and run separate wires to it for testing purposes so I can see if the problem is in the wiring from the head unit to the amp, amp to the speaker, or the head unit itself. Can I safely run this 4 ohm speaker for a few days while I figure out what's going on? Keep in mind, this thing NEVER sees anywhere near high volume. Thanks for helping out.

As long as it is not connected in parallel with the installed door speaker, sure you can do that.  However, the most likely source for the type of issue you describe is a bad speaker or speaker wire.  If you did not rewire the door speakers, then the issue is likely at the amp.  On the other hand, the PDX is likely providing too much power for the OEM door speakers and you may have just fried one of them in such a way that it only shows up during physical bouncing.  Rare, but possible.  One other thing, the four main channels of the PDX-5 are not rated for use into 2-ohms.  You are likely over-driving the amp and you will eventually fry it.  It really needs 4-ohm speakers on channels 1 through 4.Support the12volt.com

The reason I got the PDX-5 was because it WAS rated for 2 ohm speakers. I had a heck of a time finding one that was. This is from their website: "Same Power Output - 2Ω or 4Ω Configuration PDX amplifiers have the unique capability to deliver the same power output regardless of 2Ω and 4Ω loads." So now you have me wondering...and I don't know what to think. But since we never, ever power that thing anywhere near it's capability, we shouldn't be overloading it. We've never had it overheat, etc. I do believe you are correct on the wiring. That is what I want to isolate. What I did was wire from the amp, to the factory connector for all the speakers by finding another female connector and soldering the leads from the amp. This connector is located in the right rear trunk well. This way, you utilize all the factory speaker wiring. The factory Mercedes sound system isn't cheap, so I felt comfortable using as much as possible...plus it makes a very clean installation. By using a test speaker, I should be able to find out if it's the speaker itself, or the wiring from the head unit to the amp, or amp to the speaker. Those Alpine connectors leave a lot to be desired as well IMO. I certainly appreciate your input.

The fifth channel of the PDX is rated into 2-ohms, but the front four are not.  Now it may handle that load especially if it's not being pushed too hard, but these ICE-based class D amps are notorious for not liking being overloaded.  That's not likely to be causing your problem, of course.  If it was distortion from overload it would occur no matter what was happening with the vehicle.  Most likely you have a bad speaker wire connection or a blown speaker.Support the12volt.com

could also be a loose rca connection. i had a problem like that on an older MTX amp where i would randomly get noise when i hit bumps and thats what it turned out to be. funny, i could swear that the PDX amps were rated for 4 or 2 ohm loads. id have to look at the box but im almost positive that my PDX-f4 is but maybe the pdx 5 isnt...?

well, DYohn is right, copied straight from alpine website: Features and Specification SPECIFICATIONS CEA-2006 Power Ratings CEA-2006 Power Rating: (4 I? @14.4V Ƈ% THD+N, S/N: 77dBA, ref:1W into 4 I? and 2I? for mono ch.) 75W x 4 + 300W x 1 RMS Power Ratings Per channel into 4 Ohms: (@ 14.4V Ƈ%THD+N, 20Hz - 20kHz @ 4I? for 4ch.) 75W x 4 Per channel into 2 Ohms: (@ 14.4V Ƈ%THD+N, 20Hz - 200Hz @ 2I? for Mono ch.) 300W x 1 its for the marine version of the PDX-5 but they are the same amp. the specs are a little hard to understand though. it must only be the five channel though because my PDX-F4 is rated for a 2 ohm load per channel. not sure where you bought the amp from but a lot of websites have a tendency to mislabel product specs

All of the PDX amplifiers are stable into a 2 ohm per channel load. They do not give the 2 ohm rating because they specifically state that the amps produce the same power into a 4 ohm or 2 ohm per channel load.

i am an idiot wrote: All of the PDX amplifiers are stable into a 2 ohm per channel load. They do not give the 2 ohm rating because they specifically state that the amps produce the same power into a 4 ohm or 2 ohm per channel load.

they need to still be more clear about that in the specs. every other pdx amp gives you both specs

This is all really good information. As soon as I finish up the project I have going on, I will start running separate wires and speaker for that channel and see if I can resolve the issue. At least I know I won't damage anything using a 4 ohm test speaker I can set on a seat somewhere. I can't thank you enough for your help.

The PDX-5 will run 2-ohms on the sub channel only. Please see the spec sheet, excerpted here: Nowhere does it mention 2-ohm operation on channels 1-4. That's besides the point... Check your RCA's first. Drive around with an iPod connected to the inputs, and see if it goes away. If so - deck or signal wires. If not, speakers or OEM wiring.It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."