About 1 month ago a co-worker handed me a 12" speaker/subwoofer that he had laying around and it was enough to get me going on yet another DIY binge. Usually my projects take about 3x the amount of time it would take to work and just pay a professional to do it, but I have yet to destroy anything beyond repair so I have kept at it for the sake of self sufficiency. This time, however, I worry that my idealism has gotten the best of me...

I built my own enclosure using recycled speaker cabinet mdf, speaker terminals, industrial carpet, etc etc. While that took a good while, that went over smoothly and the enclosure and sub performed well in pre-mini scenario.

Then I reluctantly bought an $11 amp (shipping included) on ebay, with much absent-mindedness and naivite. Naturally, that amp was far to weak to power a 150w 4ohm woofer at--what I hoped would be--atleast 100w rms/continuous. So after ripping the car apart and wiring up that alarm clock speaker driver and briefly enjoying the low volume, high distortion sound, I began to realize I may have been in over my head. I'm a musician so I have some working knowledge of loudspeaker systems and I've done some circuitry before, but car audio is new for me.

So I upgraded the amp to a TMA 250w amp, but in the mean time I added a line output converter. What I hoped would be an easy addition and improvement turned out to be yet another variable.

Here's the synopsis:
Factory Boost CD Stereo
Adding 250w amp w/ 150w sub. 4chan amp built in crossover, DVC sub, 4ohms
Snagging line level from both left and right rear speakers
Going line into line ouput converter
Line output converter going RCA to amp
Amp bridged to mono sub

Now from my right rear speaker I initially wired + to - and vice versa. I soldered my splices. Same on right speaker, mis match. I was getting a signal and it was running to my sub, but it was too loud and distorted and turning down the line converter and amp input seemed to do nothing. After discovering my mis-matched wiring on the left, I went back and unsoldered everything. Then when I connected wires running to the sub, it would cut out the boost stereo and--obviously--nothing through the sub. Then I realized, to my dismay, that the right side (which i had already put the panel back on) was mis-matched too. It was at this point my mental and physical breakdown began.

So I move over to the right side and unsolder, then resolder the correct way and then somewhere in there my stereo cuts out and does not come back. It is currently 6am and I am in a warehouse with car panels and tools everywhere and there is a high possibility that I left my soldering iron on and it is slowly burning through something.

So for a second synopsis:
Potentially fried factory stereo
Ripped one of the factory 6x9's upon removal (yeah, forgot to mention that)
Wasted $11 on a clock radio amplifier
Mini has been ripped apart for the 3rd time in 2 weeks
Still don't have a working subwoofer. Or 6x9's. Or anything.


Have I fried my factory amp?! Have I done something worse?! Can I remedy the situation without dishing out cash?! Am I officially the biggest newb?

Any/all help greatly appreciated. This install has been going on for weeks now, stopping and starting due to tech difficulties, weather, warehouse availability, needing a backseat for family, etc etc. The only thing I can conceive of being worse than my current situation, would be if the sound system worked, but only played white noise and static at a deafening decible level at all times. On a positive note I did manage to thread the 12v power cable through the firewall without too much difficulty.

I apologize if this post was excessively long. Pardon the cynicism. Here are some poor photos from my cellphone:

 

OK.
First I suggest pulling power completely from the Boost stereo, in case it's gone in to some sort of "self protect" mode. Remember it has two power feeds, one is permanent, so you'll need to pull the connector from the back of the stereo, pull both relevant fuses (don't know which ones), or pull the battery for a few minutes.

Also disconnect the line converter, so the factory speakers / Boost stereo are back to just factory wiring.

Hopefully, the factory system will start playing again, and you can start working forward again.



Your original + to -, - to +, on both sides, would have been fine. Any issues you had then were not due to getting +/- mixed.
The reason to stick with + to - etc is so the L/R speakers don't get out of phase, which would cancel the audio and make it sound hollow. But most amps have a phase reversal switch, you could have used it to flip the subwoofer feed and kept whichever setting sounded better.


So I suspect that your line level converter links the - inputs together; when you ran with one feed crossed and one not, you were maybe driving the Boost stereo signals against each other. But I'm expecting that wouldn't cause permanent damage.


As to why you had "too loud and distorted", presumably that was simply overloaded inputs.
Do you have the in and out side of the line level converters round the right way?
Is the amp set up in "Bridge" mode to drive the subwoofer? Have you correctly wired the speaker to the "bridge" configuration of the amp?
Make sure there's no accidental ground where an un-insulated wire is shorted to the chassis.

 

thanks for the swift response. i had to haul out of the warehouse i was working in, so i was unable to get back to the computer before leaving. fortunately i unintentionally managed to stumble across your suggested troubleshooting methods via a (what i think) was a voltage surge, that shorted out the battery. this is a reoccurring issue that is linked to my aftermarket fog lights. since i was working on the car i thought i would make an attempt to repair the fog lamp issue. i was unable to repair it, but the shorting of the battery brought the factory stereo back to life.

by the way, i am a 2002 mc r50. my first and only car, bought used last february.

when i said:

"So after ripping the car apart and wiring up that alarm clock speaker driver and briefly enjoying the low volume, high distortion sound, I began to realize I may have been in over my head."

i was joking, but forgot to indicate via or whatever would have indicated that i didn't actually enjoy the low volume and high distortion. my fault on that one. dry/bad sense of humor.

i am going to head back to the warehouse as soon as i can (hopefully in an hour or two) and bring a few things to rule out potential problems, like a 1/8" to rca cable to determine whether tapping my signal is the issue or whether it is amp/sub wiring related. i'll post again later this afternoon.

i appreciate the help. have you heard of any electrical surge issues with the r50? most likely it is due to my inexperience and therefore dodgey wiring, but thought i would ask.

ps: in the photo of the amp, the wiring set up i had there was not my initial wiring set up. i was just trouble shooting. another thing to throw out there is that my sub is dual voice coil and i bridged the sub itself. this was per advice from someone at the local car audio shop, but i fear that i could have brought the sub from 4 to 2ohm and maybe my amp is not 2ohm stable.

 

I don't have much advice on the wiring, as I usually have some local pros do that for me, but I have some other advice on the quality of the parts.

You shouldn't skimp on audio parts (i.e., subs, amps, etc.). In my experience this never ends well. Generally speaking, an amp that has a peak of 250w isn't meant to power a sub, it's meant to power component speakers. That's not to say that companies don't make them, but they usually don't sound good and are often poorer quality. For a decent 12" woofer I would recommend an amp that's putting out 150w RMS MINIMUM (maybe 400w - 600w peak). Granted this depends on the quality of the woofer and what it's peak wattage is (if the sub's peak wattage is less than 800ish, I would stay away from it). I have a 12" woofer with a 900w amp (300w RMS), and it's actually on the low side of wattage. You have to keep in mind that the harder you push an amp (or the speakers, or pretty much any audio equipment) to it's limits, you're going to get more distortion, and run the risk of blowing something. Also (generally speaking again), the larger the sub, the more wattage you're going to need from the amp.

On the flip side most audio components have sort of a "sweet spot" at which they perform optimally (usually somewhere in the middle of their wattage range depending on what it is). This is where you'll get the best sound.

So the long and the short of it is... I would ditch the cheap amp and go talk to an audio specialist about what kind of sound you're wanting and what components would sound best in your car. Then, you should have a pro install it. That's what I did with my system in my '03 MC, and I've never had an issue.

 

no offense to your mammoth sound system, but that is absurd. even if it is considered "low", as far as car sub systems go, it is still absurd.. in my opinion. i'm a musician, so when i think about my PA system in my practice/rehearsal space pushing 5-800watts depending on what the neighborhood will tolerate, and how loud that is, i can't imagine why on earth someone would need or want to push that through their car. true that pushing 100w of lows is quite different from 100w of highs, but i still don't get it.

i mainly wanted the sub to improve the low end on the factory system. it is important that i don't distort the EQ to much when listening to music... not that i master my songs in my mini, but you know.

here's the crap: http://www.myspace.com/kerikino

 

Glad you mentioned this, in the car audio world amplifier outputs are grossly overstated and very far from real amplifier power outputs. Its a money game, high power rating = people buying

On the install above. I would remove all of the stereo modifications done so far. make sure everything is working properly with the stock stereo then try installing the aftermarket parts again, taking time to do it right.

The worst thing a person can do when modifying a car is rush through or take short cuts.

 

fyi the audio issues were resolved. now i just have to resolve all of those freekin broken yellow clips. just kidding... kind of.

i will be posting a video of my enclosure build tonight or tomorrow and will post a link of how to build an enclosure. or perhaps how not to build.