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AMPLIFIER POWER, FREQUENCY AND SPEAKER POWER RATINGS
Here’s what you need to know about pink noise and speaker power ratings to optimize the performance of a mobile audio system. WORDS BY DAVID MACKINNON
Over the years, several amplifier manufacturers have created four- and six-channel amplifiers designed to produce dramatically different amounts of power from each pair of channels. My first interaction with an amplifier like this was back in 2005 with a Lightning Audio Strike-Series S2.800.4 four-channel. This amp was rated to produce 50 watts of power from the front channels and 150 watts from the rear channels.
Why Stagger Power Production Capabilities? It could have been Lightning Audio’s intention that you powered the tiny 3.5-inch speakers in the front of your Monte Carlo or Mustang with the 50-watt channels and a set of 6x9’s from the 150-watt channels. No matter what they had in mind, they were on to something. Read on to find out why this is an idea that could do with some revisiting.
Signal Power Versus Frequency Have you ever sat and stared at a frequency response graph of pink noise? No? Just me? Okay, pretend I didn’t ask. Pink noise is the test signal we use to make acoustic measurements of an audio system using a real-time analyzer (RTA) and a microphone. A pink noise signal is comprised of sine waves
A frequency response measurement of a laptop computer speaker system. of varying frequencies at very specific amplitudes. What makes pink noise unique is that each octave has the same amount of energy as the adjacent octaves. When you look at pink noise in the spectral domain (a frequency versus amplitude graph), it slopes downward at a rate of 10dB per decade as frequency increases. Explained differently, pink noise has the same amount of energy the octave between 100Hz and 200Hz (let’s call that 100 steps) as it does between 1,000Hz and 2,000Hz (which would be 1,000 steps). As there are ten times as many steps, each step has 1/10th the energy.
A frequency response analysis of a pink noise test track created at a 192kHz sampling frequency. 48 Mobile Electronics June 2019
