Anyone know what would cause this? Blehm??

My rear speakers are distorting terribly whenever the balance is centered in the car or towards the front. My two front speakers are amplified via external 200 watt amp. The rear speakers are powered by the DEH-P980BT Pioneer head unit. At first I thought it was the stock amplifier, so I bypassed it. The problem is still there, so I have no idea what it could be. If I fade it to only be the rear speakers they sound fine, but as soon as I start fading the music towards the front amplified speakers the rears begin to sound like crap.

Do I need a separate amplifier for the rear speakers too? Is the headunit bad? Help please!

 

What kind of rear speakers are you running?

 

3 way pioneer 6x9's. They're pretty old, but aren't blown just yet. I also know this because they can take some decent volume when the balance is focused to the rear.

 

I'd amp both front and rear if i had the money.
why did you run an amp for the fronts and not the rears?

 

well...originally all the speakers were just on the factory amp and I turned off almost all the low frequencies at the head unit. The problem was that the rear speakers were way louder than the fronts, so I had an extra amp laying around and used it for the fronts. That made the volumes similar, but still none of the speakers could really handle any low frequencies without distorting.

If I cut the base, the rears sound okay...but any low frequencies while the balance is centered will just cause large amounts of distortion. I just got the new Pioneer HU, and want to start building the system once again.

 

because that's what people do if they're trying to get good sound quality.
when you go to a concert, is the stage in the front or the back?

 

You probably just have a loose connection at the speaker terminals. I'l solder the wires to the terminals. Make sure polarity is correct, swapped wires can also cause a "distortion" effect.

 

depends on what tickets I can afford

 

nah it's not the speaker connections. Everything else is soldered though. On the speaker terminals I just have the slide on connectors. The wire is welded to the connector though!

 

Sounds like a short. Id start with unplugging one speaker at a time and see if you can pinpoint a certain channel. Unplug it at the deck and make sure its not shorted. Or try and run the rear speakers off the amp and run the fronts off the deck and see if it does it then too (using the same outputs on the deck but front would now be rear and vice versa). This would tell you if its the deck or the speakers. If the distortion moves to the front speakers you have a problem with the deck, if it stays in back you have a problem with your rear speakers. Make sense? Hopefully you can start unplugging/swapping stuff until you pinpoint the problem. Good luck.

 

Ugh....yeah I really didn't want to rewire my entire car's speaker system, but it might just have to come down to that. Plus I'm a perfectionist...which doesn't help. I guess I can just run amp and speaker wires along the passenger side of the car.

 

before you waste your time with that, unplug the wires from the head unit and ohm them out.

you should have ~4 ohms between leads. then do a resistance check against the chassis. you should have open circuit for both leads.

 

so you mean cut them? The speaker wires are in the plug that goes into the back of the head unit, along with the power and battery and other wires.

Also, to do this would I use my DMM and just place it in line with the speaker wire? I've never been good with checking resistance even though I've had a couple electronics classes. Thanks for the help Matt.

Edit: yay for 600 posts!

 

The wires should be easily removable from the HU

 

?? the wires are all hooked into a connector that plugs into the back of the headunit. The connector is easily removable, but taking a wire out of the connector is not. I'd have to cut one.

 

With the car turned off, pull your head unit out (unless you can get to the back of it with it installed) and remove the wiring plug from it. Identify which wires go to which speakers, and use the probes from your multimeter to probe the pins in the connector that correspond to the correct wires for the speakers. With the meter set on a scale that will read 4 Ohms, test each pair of wires (RF+ RF-, LF+ LF- etc.) Each pair should read about 4 Ohms. If one pair reads much higher, look for a broken wire, or bad speaker. If one pair reads much lower, look for a bad speaker, or a short in the wiring. Next attach one lead from your meter to ground, then probe each of the wires again with the other lead. You should get infinite resistance (off the chart high) on each wire. If ANY wire reads any resistance to ground other than infinite, you need to follow that wire and see where it is shorting to ground.

Don't take this the wrong way, but I have some concern over the way this system might be wired. I am assuming that you did the wiring yourself, and I can't help but to think that if something as obvious as what you're being told here doesn't make sense to you, (and it's obvious that it doesn't make sense, or you wouldn't be talking about cutting the wiring apart) the perhaps you should be a bit more suspicious of how you have the wiring connected. This would be a very good time to make absolutely certain that the correct speaker wires are attached to the correct wires on the head unit. If you have something wrong in those connections, it will cause all manner of strange malfunctions in your sound.

 

Well it seemed like the advice was to check the resistance in each circuit while it was all wired up. I definetally appreciate your help though.

As far as how the system is wired, the Head unit has a dedicated fused power line and is grounded directly to the chassis. The front amp is also grounded to the chassis and also has a dedicated fused power line. There is a 4awg wire directly from the battery that goes to a distribution block on the inside of the firewall. From there two 8awg power cables go to the had unit and small amp for the front speakers, and a 4awg cable continues on to the trunk for a future amp to power subwoofers.

The sound to the front two speakers is sent via the FRONT RCA OUT connectors, these go directly to the amp, and then speaker wire is fed from the amp and soldered to the stock speaker wire, as I did not want to thread speaker wire through the doors. (This basically just made two wires one, creating a direct line from the amp to the speakers.)

The sound to the rear two speakers is sent directly from the HU, using the supplied rear audio out wires that are in the harness (i believe standard is green and purple...if I can remember right). This originally went into the stock clarion amplifier, which I bypassed just the other day, and then into the speakers. I bypassed the amp by connecting the rear (+)(-) input wires to the (+)(-) output wires for each side (4 total). This was done using a wiring color chart supplied by Matt Blehm's website.

All connections are stripped, soldered and shrink wrapped. I would consider myself pretty skilled with wiring as I have soldered everything from SMT resistors to trace repair on motherboards.... Either way, more advice like Tquick gave is always appreciated. Thanks again.