High Efficiency Speaker Asylum Need speakers that can rock with just one watt? You found da place.

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Dynamic range power

Posted by gymwear5@hotmail.com (M) on January 7, 2009 at 13:50:16

These are shots of the dynamics of the right channel of Frampton's famous "Do you Feel Like We Do" direct from CD and then from iPod compressed AAC. All volumes maxed and the CD was played out of a USB audio interface from my Dell laptop and the ipods analog out headphone jack (EQ out). The signal was input as an analog signal into a sound meter's electrical input (B&K Type 2270). You are looking at 1 second intervals of the complete 13+ minute song. Level are dBV re 1 uVolt (1 volt equals 120dB) Blue curve is the maximum instantaneous voltage (+ or -) for each second, The Green and Black curves are the RMS Fast Max and Min levels for each second and the Red is the RMS Maximum Slow levels for each second.

The difference between the Red and the Blue is the crest factor in the signal. The highest peak value was reached at the end "shredding" session - 121.2 dB on the ipod and 119.0dB on the CD. Though both topped 118dB may times. The interesting thing is that the crest factor is almost always above 10dB and averaged 12.8 for both signals reaching a maximum at around 20.4 for the CD 19.5 for the iPod.

The of the red curve as the RMS power your amplifier is using and the blue curve as the part of the signal you don't wish to clip. That means you need 20dB or 10x more voltage than what the RMS voltage is for this recording.

Lets say your power amp is cruising along at 1 watt RMS - hey you like the song cranked up - your frugalhorns are putting out 95dB at your listening seat. Is your 10Watt SET good enough? Well 10 watts gives you a 13dB headroom factor (adding 3dB for the move from RMS to Peak), but is clipping mightily throughout the playback - at least until the middle section of the song where it will just clip occasionally. And for the highest peaks you are going to need 100Watt to pass without clipping.

High efficiency rules! Can you imagine an 85dB loudspeaker (pick your favorite) needing 1000Watts just to NOT clip!

This post is made possible by the generous support of people like you and our sponsors:

Atma-Sphere Music Systems, Inc.

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