What is Dynamic Headroom?

[keyser]

Hi all,

What is dynamic headroom? I've seen it expressed in db's, but I don't understand what it means.

 

[jan.didden]

Hi all,

What is dynamic headroom? I've seen it expressed in db's, but I don't understand what it means.

Suppose your amp puts out 50W continuous under load. This is ultimately limited by the supply voltage, that sags under full load.
But with music, there is never a continuous full load, there is full load short peaks. Because of the supply caps, those short peaks can be deliverd to the speaker without the supply getting time to sag. The output power is there for higher with music, say 70 watts.
The difference between those 50 watts and the 70 watts is the headroom. 10*log (70/50) = 1.46dB headroom.

You also immediately realise now that an amp with a regulated supply has 0dB headroom.... Marketing won't like that, ma.

Jan Didden

 

[rjon17469]

So, how would you calculate that upper power figure (in the case you mentioned, 70 watts)?

Reece

 

[keyser]

Thanks Jan,
Your explanation was very clear, but I still don't get it completely. How long is such "short peak" you are talking about. What determines the speed in which the maximum voltage available from the capacitors drops? Has dynamic headroom got something to do with stability of the amp? (I mean its ability in delivering double the current in half the load)
keyser