Automotive tuning guide

By Philipp Paul Klose
https://www.linkedin.com/in/philipp-paul-klose-280813145
https://kurzschlussklose.wordpress.com/

Introduction [Top]

Car cabins are one of the hardest acoustic environments in which to create quality sound reproduction: the space is small and has massive room resonances up until the lower midrange. We have surfaces that create nasty reflections from glass or metal, some acoustic dampening materials are super absorptive and trim pieces rattle. The speakers can't all be directed at the listener(s) and the car itself produces a lot of noise by wind, rumbling tires and its powertrain. It seems the only good thing is that we know where the listeners are and that they will not move.

Still, all is not lost! It is possible to have good sound reproduction in the car – it's just a little bit harder than in other environments. Thankfully, DSP power is available, and it is more than useful in cars. Bear with me and we will make a super sound system for your car!

The goal of this app note is to give you a primer on how to approach measurements and the application of DSP in order to improve the sound in your car. Of course, not all special situations, edge cases and caveats can be covered. For ease of reading, the app note is split into four separate pages (linked below).

This app note is not about wiring, electrics/electronics, speaker selection or speaker setups. Basic knowledge of DSP usage and measurements is required.

Setup [Top]

For this app note, it is assumed that you have already installed the speakers and the amplifier in the car and the electrical and electronics work is done.

Prerequisites:

REW installed on your computer (version 5.20 is used for the examples shown here) from https://www.roomeqwizard.com.
A car with a working miniDSP C-DSP amp setup. The examples in this tutorial use the Harmony DSP 8x12, so available options in your tuning tool may differ if you are using another C-DSP amp.
A microphone or microphone array, as described in the section "Microphone Techniques for Measurements in Car Cabins."
Car preparation for tuning:
1. Hook your car up to a 12V battery tender or charger
2. Turn the headlights off (if possible)
3. A/C off
4. Turn off auxiliary devices (winches, lights, fridge, additional heater...)

Take care of your hearing! Drive safely!

List of sections [Top]

For ease of reading, this app note is split into four separate pages:

Microphone Techniques for Measurements in Car Cabins looks into various microphone techniques for measuring sound in cars.
Measurement Approaches in Car Cabins describes the two main approaches to measurement, and when you should use which.
Tuning Procedure: DSP Modules and Their Use explains how to use the features of your DSP.
Sound "Philosophy" and Challenges in Car Audio covers some best practices that are missing from other car sound tutorials.

Applicable miniDSP products [Top]

Car audio DSPs

C-DSP 8x12: Premium 8-input, 12-output car audio DSP
C-DSP 8x12 DL: Premium 8-input, 12-output car audio DSP with Dirac Live
Harmony DSP 8x12: Powered 12x40W, 8-input, 12-output car audio DSP with Dirac Live

Acoustic measurement

UMIK-1: Economical calibrated USB measurement microphone
UMIK-2: Reference USB measurement microphone
EARS: Economical jig for binaural measurements
UMIK-X: Distributed microphone array with 8 or 16 microphones
UMA-16: Compact microphone array with 16 microphones

Wrapup [Top]

That's it! I hope you had fun!

Automotive Sound with miniDSP Products and REW