Why milliseconds determine sound quality - practical tips for a harmonious sound image
Runtime correction in the car - what it does and how to set it correctly
If you want to achieve a perfect sound image in your car, there's one thing you can't avoid: delay correction. But what exactly does this mean and why is it so important for a realistic listening experience? In this article, we explain in simple and practical terms what delay correction is and how to set it correctly.
What is runtime correction?
In a typical car, the driver does not sit in the middle between the loudspeakers, but closer to the left side. This means that the sound from the left speakers reaches the ear earlier than that from the right. The human brain uses these minimal time differences to locate sound sources. If these travel times are not corrected, the sound image appears unbalanced or "pulled to the left".
Time alignment ensures that the sound from all speakers reaches the listener at the same time - in other words, that delays are built in to compensate for the natural asymmetry in the car.
Why is runtime correction important?
- Centers the sound image on the listener
- Improves the stage image (imaging)
- Creates a more realistic, spatial sound
- Ensures harmonious interaction between all speakers
Without delay correction, music often sounds "out of place" or intangible. With it, it seems as if the singer is standing right in front of you. The instruments "stand" in their place and are clearly locatable, as if you could point your finger at them.
How do you set runtime correction correctly?
1. measure speaker distances
The aim is for all sound sources to reach the listening point at the same time. The ideal setting is on the driver's seat. In other words, we move all the speakers away from us until they are all at the same distance from our ear. You can imagine this desired distance as an "orbit" on which the speakers are lined up.
To begin with, we measure the distance from each speaker to the driver's ear. The best way to do this is to use a tape measure or folding rule from the speaker to the headrest.
Now determine the speaker that is furthest away - it determines the orbit - and subtract the distances of the remaining speakers from its distance. You then enter the difference in the DSP for the respective channel so that they also land on this orbit. Example: The subwoofer is the furthest away at a distance of 2 m from the ear, the front left speaker is 0.80 m away. Then note the difference of 1.20 m, i.e. the necessary delay, for the front left channel. The front right speaker is 1.30 m away from your ear, so the delay value would be 0.70 m for the front right channel.
2. convert distance into milliseconds (if necessary)
A rule of thumb: sound requires approx. 0.029 ms per cm. Example: If the right speaker is 30 cm further away than the left speaker, the left speaker will have a delay of approx. 0.87 ms.
3. enter distances into the DSP or radio
Our AXTON DSPs (digital sound processors) A544DSP, A594DSP or A894DSP offer you the option of entering the runtime for each channel in centimeters or milliseconds.
4. fine-tuning with test music
Use well-produced pieces of music or test tracks to fine-tune the running times. Voices should come clearly from the center, usually somewhere between the rear-view mirror and the steering wheel, and should not "wander". So if the singer seems to have a mouth two meters wide, check your settings again.
Conclusion
Time alignment is an essential tool for getting the most out of your car hi-fi system. It corrects acoustic imbalances caused by the asymmetrical seating position and ensures a realistic, centered sound image. With a little patience and sensitivity, you can achieve an impressive difference.