DIY Car audio system
Here’s a project that I did a long time ago (back in 2009 actually). Anyhow I thought it would be nice to keep a record of it here on the blog.
Everything seen here was DIY and done from home in the car park. I used a fairly simple equipment setup as space was a concern. You’ll probably find the equipment really old compared to what you guys have nowadays. I had some stuff lying around and I like the old equipment cause I’ve tested some of the new stuff and they just do not seem to be built the same anymore.
Head Unit: Pioneer DEH-P80RS
Front speakers: 4″ MB Quart 2-Ways
Sub: 8″ Rockford Fosgate 4 Ohm SVC
Front Amp: Nakamichi PA-304
Sub Amp: Nakamichi PA-302
As you can see, I’m running a simple 2.1 system. The HU was choosen for the 3-way crossover and time alignment capabilities as I did not want to install a separate signal processor. It also has the ability to turn off the internal amp (reduces noise) and has high volt pre-outs for better SNR. Great unit overall, but I wished it had a parametric EQ for better tuning.
The 2 nakamichi amps are very clean as there is no extra circuitry for crossovers or signal processing, again in line with my need to lower the signal noise. the 304 is run in 4 channel mode (4x45W @ 4 ohms) to power the L/R mids and tweeters. The 302 is in bridge mode (1x160W @ 4 ohms) going to the RF sub.
I was looking for Sound Quality so did not see the need for high power amps or a large sub. Thus the 8″ RF unit in a 0.29 cubic foot sealed enclosure.
Everything was designed to be removable so that I could go back to stock and keep my equipment.
The front speakers are on the dash as far away as possible to minimise path-length difference. The pods are made of fiber-glass and MDF rings. A mould of the dash and A-pillar was taken to build the base of the pod, then the MDF rings were added and the whole thing fiber-glassed to seal it up. A layer of rubber coats the inside to reduce resonance and is filled with polyfill to increase air mass. It was then wrapped in speaker cloth and attached with silicone to the dash.
The head unit is cleanly wired. All connections are soldered for conductivity, covered in heat-shrink tubing (I do not like electrical tape as it leave a sticky residue and looks horrible) and tied off. I did not use most of the stock wires except for ‘acc’, thus all unused wires were heat-shrinked over to prevent shorting and tied off. Ground goes directly to chassis and power is straight from the battery through a 1-4 distribution block. 2 gauge wire is used from battery to block with a 60W fuse in the engine bay 6 inches from the battery. Signal cables are home made with gold plated connectors and heavily shielded coax cable.
Due to the lack of space and wanting the signal cables to be as short as possible, the amps are placed under the car seats. 8 gauge cables are used for power and ground. All power and signal cables were not allowed to cross to prevent introducing noise into the system. 22 gauge is used for remote signal from the head unit wired in a daisy chain. The remote wire does cross the signal cable, but it was done at 90 degrees to prevent noise. I’m not entirely pleased with the amp presentation under the seat but am too lazy to work on a fiber-glass cover to beautify it.
The sub is placed in the trunk within the spare tire to save space. I wanted to keep the spare tire so a mold of the inside of the rim was made from fiber-glass and the enclosure was made. I did some rough calculation before making this to ensure that I had enough air volume for the sub. 0.3 cu Ft is recommended, and I estimate that I could get very close to that by measuring the internal radius of the rim. I had a bit of space above the rim and below the read covering board so it all worked out. The sub thus sits inside the spare tire covered by the original board and no space is given up in the trunk at all.
Tuning was done with a RTA and a pink noise testing CD. Unfortunately the head unit only has a 16 band graphic EQ, so I could not entirely flatten out the overall response. However for my purposes I don’t think I need to add in a parametric EQ for better tuning. I’ve not had problems with vibrations yet, but some sound deadening would be nice.
Everything was done at home over the course of 1 1/2 years when I had the time away from work and other hobbies. Like everyone else, it will always be a work in progress.
Unfortunately I didn’t take picture during the build as I normally do not post things and I’ve been DIYing since 1996 on my cars. What you see here is basically the finished product, but I can answer any questions if you are wondering how anything is done.
Some extra pictures below.