Dynamic Headroom?

DH is an aspect of an amp that allows the amp to exceed its rated wattage by a certain number for very brief periods.


In certain movies, specifically action movies there are times when the sound level will go up drastically...explosions. The DH allows the amp to cope with this sudden, short burst of sound.


To understand DH you have to understand the way sound is measured.


For every 3 db the sound level doubles. To produce that 3 db the amp power has to double.


Let us start with an amp rated at 100 watts/channel with a DH of 1.5. This means that when called for the amp can produce 150 watts for a brief instant of time. If the DH was 3 db than the amp could go to 200 watts.


NAD has been famous for the extreme high DH. The amps I use are rated at 75 watts/channel but the DH is 6 db. That means that they can go to 300 wats when called for (75 x 2 = 150 x 2 = 300)


Just as a point of reference a DH of 1.5 is a bit low. But if you are starting with a high wattage amp, then that is not a huge problem.


Hope this helps


Lee

Lee-


"Let us start with an amp rated at 100 watts/channel with a DH of 1.5. This means that when called for the amp can produce 150 watts for a brief instant of time. If the DH was 3 db than the amp could go to 200 watts."


My math is rusty, but I believe the relevant equation for power, expressed in decibels, is L1=10logW1/W2, where L1 is decibels (dB) and W1 is power with regard to a reference power, W2. Hence, if the reference power is taken to be 100W with a desired level of 150W, our L1 becomes 10log(1.5) which is about 1.76dB. I think, running the equation to solve for 1.5dB, we get an actual power of 141 watts. The 3dB increase of 2x the starting power is of course absolutely correct.


Rather interesting is that this fairly enormous increase in power (from 100W to 200W) results in only 3dB of loudness, which to the ear is not a whole lot....it takes a difference of 10dB, or 10x the power expended, to produce a sound which is apparently twice as loud! Thus the value of either high power or high speaker sensitivity in sound reproduction, particularly in Home Theater where large shifts in level are common.....


-Aerlith