Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics.

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Re: You're Blinded By Believing The Science Being Used Reveal Everything!

Posted by tomservo (M) on June 23, 2006 at 14:49:12

In Reply to: You're Blinded By Believing The Science Being Used Reveal Everything! posted by thetubeguy1954 on June 23, 2006 at 13:10:24:

Hi

Outside the tiny relatively unimportant world of esoteric audio, lies a VAST world of critically important electronics. It has been both the advancements in measurements and computer modeling that permit the understanding and design of things like cell phones and computers (digital circuitry controlled by analogue effects). Things that are minor in audio like skin effect, dielectric absorption, stray inductance are things that govern electronics in the MHz..
For there to be “something missed” would suggest that audio electronics are unlike all other forms of electronics, that the dozens of kinds of measurements used in RF and electronics do not measure some wave aberration in the signal is highly unlikely.
Consider there is only time and Voltage, if you measure the Voltage 100,000 times per second you catch the signal from an audio perspective. The rest is data display and analysis.
The problem is, if you have high resolution measurement’s, is that there isn’t much that says “what matters” or what sounds like what, or, what to do to fix it.
All of this you learn by listening and measuring, this is the art or experience part..
Understand there are lots of Types of measurements, some matter (to me) some don’t, THD isn’t useful but an FFT of the fundamental and harmonics is.
Is it possible to miss something entirely? You bet, but, its unlikely everyone else wouldn’t miss it too, over and over.

You ask about “live” and mention the Blizzard of information.
Good point, loudspeakers are by far the weakest link in the chain, they scramble the input signal up in a number of ways.
On top of that, you put it in a room and depending on its directivity, it interacts with the room too.
Mic placement and recording technique have such a huge impact it is hard to describe how the modern multi mic technique makes a modern “stereo image” except that it is painfully constructed (usually) when present. Simple (2 mic) recordings also have a following.

Think about speakers this way, an amplifier would be considered broken if it couldn’t reproduce a complex signal like a square wave (or music) mid band.
There are VERY few loudspeaker that can reproduce a square wave over any significant bandwidth or position. A Manger being one example (the best speaker “in time” I ever measured) that unfortunately has “other” flaws (like high harmonic distortion).
What are marketed as “coherent” loudspeaker’s are still not coherent “enough” to preserve wave shape. Loudspeakers, even individual drivers, are dispersive, spread an impulse out in time. People argue about absolute polarity using speaker systems that have hundreds of degrees of acoustic phase rotation “in band”, polarity of what, where do you start?.
Magazines publish response and designers use curves taken with impulsive test signals like MLS which provide a “pretend” phase curve based on a Hilbert transform of amplitude, not an actual measurement of phase.
An amplifier would be considered broken if it had 30% thd mostly 3rd harmonic, yet many woofers reach this level “at the bottom” at about ¼ rated power.
An amplifier would be considered broken if it exhibited 6 to 10 dB of non-uniform dynamic compression going from small to full level but most speakers do this.
I know this because I have measured it.
Wonder why it’s so far from real?

Tell you what, if you live near Chicago, I will let you hear what an objectivist, highly measurement based horn system sounds like if you want. Then decide if I’m barking up the wrong tree.

Tom

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