Old subs, new car.

Iboc_C64

Iboc_C64

New member
Hey guys, I have run in to a little snag installing a pair of old 10" Rockford Fosgates in a "Competition Bandpass Box" in my 2009 WRX. At the moment I cannot afford a new Head Unit or replacements for the OEM speakers, due to a series of misfortunes on my part over the past year, I have not had as much play money as I expected. So, I was going to leave the stock system alone until I could get an HU, but a buddy of mine offered me his 2 10" Rockford Fosgates for FREE!!! I could not pass up that deal, even though it will take up my entire trunk, I will deal for the price of free! Anyway I did manage to pick up a forward to reverse wiring harness to use as a custom T-Harness, and I grabbed an old Scosche FAI3 that I gave to another friend 5 years ago and he stopped using it. I used my trustee old Kenwood Excelon KAC-X621 2 Channel amp that use to drive 2 700watt Kenwood 12" subs. I wired it all up, used a 1500watt amp wiring kit that was leftover stock from the former Radio City. I turned it on and the speakers move, but they canceled each other out or something because they did not produce sound, they just moved.

Now, to be fair, these are OLD speakers, one of them the centercap fell off from it, so I wasn't sure they were both good. But the moment I disconnected 1 sub, the other came on full power and sounded amazing! So I figured, maybe the other one was blown? I disconnected the other sub, and reconnected the first, still great sound! So now I am trying to figure out how both channels can work independently, but cancel each other out once they are both connected. Only things that I can figure is that one of the subs is wired backwards inside the box and once they are both connected the audio cancels itself out. The other thing I thought of is that perhaps its an impedance problem, maybe these are 8ohm subs? But they aren't bridged so that should not be an issue since this amp supports Impedance of 2ohms to 8ohms. I know its not the amp because it displays no error messages and works great when I hook it up in my Grand Am with the 2 12" Kenwood Tornado's in a Ported box. Anyone got any Ideas?

 
the polarity is backwards on one of the subs. swap the + and - at the box on one sub and try it

 
Also, I assume you already have a low-high level converter to feed the amp?

And its unnecessary, but to clean up the sound a bit, you probably want to crossover all of the low freqs. away from the door speakers.

 
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The fact that the stock HU adjusts the Bass down as volume goes up is a bit annoying, but the system doesn't suffer from it as much as I expected. I set the Bass at the Headunit to zero and turn up the input sensitivity and volume on the amp. I also have the low pass filter on the amp enabled and set at about 100hz. This is far from my first stereo, its not even my first stock HU retrofit for subs. I have done 3 stock HU setups previous to this one and done about 12 stereo installs in the past 10 years. The Scosche FAI 3 is a High to Low converter as well as a speaker level adjustment location. Its and older design item has many different uses, but I am using it as a Line-Out Converter. I also don't get any electronic feedback from anything in the car except for when the HU is off and power is first applied to the amp when its cold, then I get a little Fuel Pump interference, but it hasn't shown back up since I first powered up the Amp. I haven't gotten the chance to check, but I have a feeling the speaker with the reversed polarity is the one with the wire connection location's colored caps screwed on backwards. Whoever put the box together probably realized thier mistake and swapped the caps as a reminder to themselves. According to the labeling on the box though the polarity is right so I am going to take out the subs this weekend and check the wiring inside the box. The box also does't have any stuffing in it anymore so I got to find something to replace that too.

 
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Yup, polarity was the problem. The polarity was switched inside the box on the side that had the colored speaker connections switched. The colors were backward from the labeling on the box. Once I reversed the polarity everything worked properly. Incedentally, the reason the one speaker I had hooked up in mono configuration while I thought about what else could be wrong was actually connected with reversed polarity, which is why is sounded louder than it should at low volume and not loud enough at high volume. The whole system sounds very nice now. Thanks for the advice everyone, this is my first bandpass box so I guess there is always room to learn a thing or two huh? Another question that I still have is, since these two speakers share the same speaker cavity, should I shut off the stereo mode of the amp and run them mono or will that not matter now that they are properly connected? Im just concerned that if they are in stereo, having one speaker vibrate more than the other is trying to could cause distortion couldn't it? Of course, I don't really want to lose a sound channel unless it may cause a fair amount of distortion or speaker damage.

 
I love subwoofers. I especially like the way that deer and moose are no-where to be seen when you use them. Headlights don't seem to frighten them, but they certainly seem to hate subwoofers. This is probably why I never hit one in the 6 years I ran subs in my old car.
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