Transient
Definition
A transient is a short burst of energy in an audio signal. Drum hits, plucked strings, bass notes, and orchestral peaks are transients. They last milliseconds, not bars, and they sit well above the average (RMS) level of the track.
The ratio of peak level to average level is the crest factor. Typical recorded music has a crest factor of about 10 to 20 dB. That means a passage that averages 80 dB can spike to 90 to 100 dB for an instant.
Formula
Each 3 dB of peak-to-average difference requires a doubling of instantaneous power. A 10 dB crest factor needs about ten times the average power on the peak. A 20 dB crest factor needs about 100 times the average power for that instant.
That is why an amplifier that sounds fine at a moderate average level can still clip on transients if it has no headroom.
In a stereo system
Transients are the reason wattage and headroom matter even when you do not listen "loud." The amp must supply current and voltage for the peak, not only the average.
After the peak, the speaker cone must stop. Damping factor describes how well the amplifier controls that motion. Poor control after a transient sounds like loose or lingering bass.
If transients sound harsh, compressed, or "edgy" as you raise the volume, the amplifier is likely clipping those peaks. Back off, or use an amp with more spare power.
