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  • Writer's pictureJim Cathey

New Year, New Drive - Car Audio

Updated: Mar 25, 2023

Happy New Year. As we drive into a new year, I am shifting gears a bit ( pun intended). Posting an update about my 1976 MGB Roadster, which has been in the makeover for the past year.

Although much of the basics are the same as home audio, car audio has significantly more challenges, especially with the after-market and retrofit of a vintage car. The listening room, cockpit in this case, is like a fishbowl with not only glass but a variety of materials and angles not conducive to the best audio performance. These challenges do not include complications from a convertible car.

The challenges continue with limited areas for ideal speaker placement or space for the right speakers. Even with custom modifications, the environment will be harsh. Where possible, treat the cockpit with dampening materials on the floors and walls, similar to what you would do with an in-home listening room. Modify other materials where possible, like the seating, dash, ceiling, and flooring, similar to a home where you need to manage reflection points. Custom speaker pods will provide flexibility in the speaker positions and the chance to raise the tweeter and mid-range to ear level or close to it. The absolute must is an amp with DSP capability and lots of power.

Because of the limitations in a car, managing the audio waves can only be done via a DSP. I would frown on 2-channel audio in a home environment, but not with a surround-sound system or, in this case, a car; it's a must.

Like all stereos, the starting point is power; lots of consistent, clean power. And in combustion automotive, the sources are your battery/alternator. Power, the source and cables often get overlooked in a DIY car audio retrofit. Often, we don't look at the alternator's amp capacity, the power cable, the health of the car wire harness(es) or the car battery and the need to separate that for the audio system. If you have a project with a vintage car, start with the power, just like a home audio system. Is the installed alternator producing enough amps for the car systems like the heater, headlights, electric radiator fan, heating/air conditioning fan, heated/cooled seats, etc? Then add what you need for the new stereo and those hungry new amps. There are many websites to check how to calculate the amps. But in the end, you may find that the alternator and cabling need to be replaced. And given the amp and distance, what is the wire gauge needed? When in doubt, go to a smaller gauge; my default is 0 gauge with oxygen-free cable. Yes, it's big, but it will have the least resistance.

I currently have an MGB Roadster in the middle of a restoration, and the original alternator was a small 45 amp capability. In addition, the battery is in the back of the car, and the new stereo amps would be in the trunk. Had to upgrade the alternator to 135 amps and replace the cable to the battery for a 15' run to a 0 gauge cable. That should be plenty of headroom for the stereo and the car electronics, but to ensure clean power, a dedicated battery will be wired in for the stereo to draw upon. Hence, unlimited power at any peak draw moment and the option to run the stereo without running the car engine or putting the car battery at risk. This should also eliminate any electrical noise from the car electronics or car battery. Also replaced the three wiring harnesses in the car; they needed to be replaced based on age and would surely have introduced noise if they were left in.

Yes, what you're thinking is right; complete overkill on the power. However, it will give the best power option for the stereo and provides additional flexibility if I add to the system later. There will be lots of power headroom for future stereo expansion and electric car upgrades. And the need for more power has already arrived. The initial test system did not have the performance I expected, so moving to bigger amplifiers, speakers, and subwoofers required additional power.

The 2nd system going in has the following key specs:

· 1976 MGB Roadster (The actual car I drove in high school).

· Front Speakers: Focal ES 165KX3 Elite K2 Power Series 6 1/2" 3-way component speakers

· Rear Speakers: Focal EC 165K K2 Power Series 6 1/2" 2-way car speakers

· Amplifier for Front and Rear Speakers: JL Audio VX800/8i 8-channel car amplifier with DSP 75 watts

· RMS x 8 Subwoofer: JL Audio 10W6v3-D4 Series 10" dual 4-ohm voice coils.

· Subwoofer Amplifier: JL Audio VX600/1i Mono Amplifier with DSP 600 watts RMS x 1 at 3 ohms.

It will be challenging to finalize the speaker placements for all the speakers, given the small size of the MG. The front will probably have a split where the footwell side walls and a part of the door will collectively accommodate the 3 component speakers. The passive crossovers will be eliminated and replaced by driving each speaker directly from the JL Audio VX800/8i, which can be an active crossover with user-selected frequencies. The rear speakers will find a home in a false wall on the bulkhead between the cockpit and trunk. It's expected to share that location with the subwoofer, provided the vibration can be managed with Sorbothane.

The front and rear speakers will require some fabrication so that the speakers will disappear in the car and produce audio with no visible or limited visible appearance. The dedicated stereo battery, amplifiers/DSPs will all be in the trunk attached to the bulkhead wall between the cockpit and trunk.

I will post an update once the final audio system is installed and include all the components, performance, and reference links. Posting some pics meanwhile that I managed to click at the garage.

Note: the cockpit and trunk floors and walls have all been treated with sound-dampening material before carpeting with Dynamat and Thermozite where needed for heat dissipation.



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