From ssiegel@rochester.rr.com Mon Jul 02 06:12:01 2012
Subject:Re: Alto amps - Peak Power and RMS

This topic is definitely a hornets nest of conflicting technical issues. One of the big mismatches is that speaker drivers have maximum power handling specifications that are measured completely differently from the way power amplifiers are measured. Speaker power handling is based on a pink noise input with 6 dB peak to average ratio; amplifiers are typically meausred with sine waves. Furthermore, the speaker rating just tells you what amount of power (or voltage) can be applied to the speaker to make it break. it doesn't mean that you can actually drive it that hard, because it may start to sound bad at 6 dB below that point. Most of us will consider the maximum USEABLE output of a speaker system to be reached when it starts to sound bad, regardless of how much average power is being delivered.

In fact, the average amplifier power doesn't really matter, either, because (as Bruce points out) music has a much larger peak to average ratio than 6 dB. For example - assuming a 10 dB peak to average ratio for music (could be more, but isn't usually too much less), an amplifier with 100 watts "peak" output would never be driven to more than 10 watts of average output. So, the rating of "how loud will the speaker get" depends on a mix of the following:

1. What is the true peak output voltage that the amplifier can (cleanly) supply to the load?
2. What is the peak level that the speaker driver can create before it sounds bad. You will NEVER find this on a spec sheet. This is what separates the men from the boys in loudspeaker driver design. Well designed drivers will sound better when operated near their mechanical limits.
3. What is the sensitivity of the speaker/acoustical system.
4. What is the spectrum of the music. Wider bandwidth requirements may reduce the max output capability of the speaker system. Typically, woofers will reach their excursion limits well before their thermal limits.

--- In CloneWheel@yahoogroups.com, Bruce Wahler wrote:
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