First of all, I’m not a professional, just someone who used to be obsessive about mobile audio. So, please forgive any misuse of terms or definitions. Digital time alignment (abbreviated as TA) was the driving force behind my first active system. Based on recommendations by this forum, I put together a laptop-based measurement setup to help with setting time delays.
Long story short, I was never satisfied with the results. I put away the microphone and cables, and decided to use a different set of measuring devices: my ears. I experimented for weeks, and developed a way to set TA by listening for specific cues. The results were fantastic. The reason my method, with practice, will achieve better time alignment than any sophisticated measurement system is simple: it’s customized to every individual, and their vehicle interior.
With correct application, this method achieves immediate improvements in imaging, staging, impact, and transparency. Bass should become thinner, but in a good way - lean, with great impact. The sub-bass shouldn’t come from the back of the car, or even up front – it should be completely unlocalizable. Midbass should be solidly up front along with the rest of the center image.
TA will be calibrated:
- Using your own ears
- Taking into account your own hearing (the same sound is heard differently by everybody... and much more so by microphones)
- With your head in your everyday driving/listening position
- Taking into account all in-cabin reflections and absorptions, including your own body’s effects
The method costs nothing but time and patience. An audio file of pink and white noise will be used for tuning and can be downloaded free here: Burn-in wave files: white noise, pink noise, frequency sweep, channel mix
The method assumes that your system is an active one, with each channel individually adjustable for time delay. It is developed and written for a 2-way front stage with a mono subwoofer channel and no rear speakers, though it can adapted for any other active system, no matter how many channels. Note that there is only one sweet spot per calibration.
Here’s a preview of the method for a typical 3-way system:
While playing pink and/or white noise through system,
- Isolate sub and passenger side midbass (mute all other channels). Align drivers.
- Isolate sub and driver side midbass. Align drivers.
- Isolate driver and passenger midbasses. Verify time alignment and center image.
- Isolate passenger side midbass and tweeter. Align drivers.
- Isolate driver side midbass and tweeter. Align drivers.
- Isolate driver and passenger tweeters. Verify tweeter alignment and center image.
- Verify front stage alignment.
- Normal up the system and evaluate.