My Dremel Tool Workstation

Car Stereo and Speaker Installation

This is a continuation of where I last left off regarding my battery drainage problem. The factory amplifier unit had a short circuit so I had to remove it to solve the battery problem. But without the amp, I cannot listen to any music in my car. To replace it, I could either order it from the dealership or try to find a used one in good, working condition from a junkyard.The first option would cost too much (the dealership quoted over $700) and the second option would take too much time and hassle.

Given these choices I decided to replace the factory installed stereo unit and speakers with aftermarket equipment. I’ve been wanting to do this anyway since my car is 15 years old and the existing stereo unit was obsolete.

I purchased a Kenwood KDC-MP245 CD Receiver from Crutchfield. It has four pre-amp channels at 22 W RMS/50 peak of power each.

I also ordered 2 pairs of Polk Audio db651s 6 1/2″ speakers. These speakers are rated for 6 – 55 W of RMS/165 peak power, frequency response of 50 – 22,000 Hz. and a sensitivity of 92 dB. Sensitivity is another term for efficiency. It is a measure of how well the speaker converts audio signal power into sound as opposed to being wasted as heat. The higher the better.

I also got a 50′ spool of 16 gauge blue speaker cable. When replacing factory default speakers with new ones, there are generally two options for wiring the speakers to the stereo unit: use existing wiring or route new wiring. The first option is less work. The second option means you have to take things apart but the sound quality is better. Specific to the case of my car, the factory component amp was a big factor. The existing stereo fed audio input to the amp. In turn, the amp was driving two tweeters, four speakers, and a sub-woofer. The existing wiring configuration was useless for a four speaker only setup. I went with the second option.

The most difficult part of installing aftermarket car audio equipment is routing the new cabling.

The front two speakers were located in the doors which meant that I had to take the door panels off.

There is a wire harness that goes from the door speaker to a junction box in the interior of the car.

The plan was to thread the new cable through the wire harness. But I had to clip and pull out existing speaker wiring to create slack first.

After that, I threaded through the new cabling. The positive and ground leads were fastened to the speaker terminals with crimping nuts.

Making the back end connections at the stereo unit was pretty straightforward.

Installing the rear speakers involved taking the rear passenger seating off.

Overall, it was a big project that took three days to complete. Because it involves access to electrical schematics/wiring layout, knowing where things are located in the car, some skill in electrical work, troubleshooting, and taking apart many different sections of the car interior, it is not recommended for the faint of heart.

The following videos demonstrate the results.

Kicad Schematic for Minty Boost

Minty Boost is an open-source hardware design developed by ladyada. It is a battery powered USB charger for mobile devices such as cell phones, including the iPhone.

ladyada used Eagle to design the PCB and had it manufactured by a PCB shop. I don’t like Eagle because the freeware version has limited capability and I don’t want to pay for the full version. My plan is to use KiCad, which is open-source, to recreate the latest schematic done by ladyada, and make the PCBs myself using homebrew techniques. 

My KiCad schematic is shown below.

The design is centered around the LT1302 fixed 5V DC/DC converter with high current output. Next, I have to create footprint modules for a few of the components.

Skull Splitter Candle

Arrogant Bastard Ale Candle

Wine Candle

Rhinocerus Candle, artwork by Albrecht Dürer

Rainwater Madeira Candle

Winter Persimmon Wine Candles

Photographic artwork courtesy of “R Elgin” of The Marmot’s Hole.

San Pellegrino Candles