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In Reply to: RE: Dick Heyser posted by tomservo on January 26, 2023 at 14:29:09
Or at least a couple things important to Audio.
In his day, there were ways to measure Frequency response but time blind, there was no "phase response" AND if you set up a cost no object HP network analyzer, you could get phase if close enough but the speaker was buried in time delay related phase shift and reflected sound.
His TEF machine first captured "how far away is the speaker" at the highest frequencies (most precise) with the Energy vs Time Curve and then measured the magnitude with actual loudspeaker phase. Not just that but many measurements could be taken indoors now because of the Frequency windowing (much better noise immunity than time windowing)
With that, many things could be seen like the first waterfall displays, impulse response, step response, predictions of intelligibility and many other useful acoustic tools. It did not become the dominant technique because it was patented and narrowly licensed (like Beta tape was).
I even dragged an early TEF into the great Pyramid to measure the sound in the Kings chamber.
I can attest first hand to one way his discoveries went on to effect audio.
In the video "How we hear" i was asked about "hearing" and how we sense direction and distance.
https://www.facebook.com/watch/126113687424773/423500813293005
In the part describing the notches in your hearing, Doug Jones (in the original video i linked and was a friend of Dick's) was one of those people, he used the TEF machine to take those "in ear" measurements that discovered the last bits of "how we hear" direction and height. The LEDR recording Doug and co made used those notches to make objects move in the stereo image.
Those things i described about developing the speaker were actually following along an imaginary speaker Dick described late in life in one of the papers Doug had, a broad band single point in time and space.
With his TEF machine i was able to make one as he described theoretically in that video and has been the primary type of speaker we made.
The way i found was also one that had horn loading and the directivity of a large constant directivty horn.
How was also a question the video guy asked. See the "Expansion rate" video for a dry marker scribble.
Tom
Follow Ups:
In the first place speakers and every thing else sound different in different rooms so it's a logical fallacy to assume frequency response measurements of speakers mean very much, since those measurements are never consistent for different rooms. As I mentioned yesterday in another post on this thread some of the most important characteristics of sound cannot (rpt cannot) be measured. Examples: Air, transparency, richness, naturalness, soundstage dimensionality, coherence, presence, things of that nature.
So, this is the *big conundrum* for audiophiles, one that Dick Heyser was unaware. If we can't measure all the characteristics of sound where does that leave us? It leaves us having to get skilled at listening. This is the ONLY WAY FORWARD. In order to find the golden path to audio nirvana you have to be able to analyze what you hear and figure out what's wrong in the system and how to deal with it. Most audiophiles I reckon are at least two paradigm shifts behind the power curve.
Measurements can be useful when mapping out the room to determine ideal locations of speakers and locations for room acoustics treatments. But other than that measurements or specs serve little purpose or guidance for audiophiles how to proceed. There are a great many hurdles in thinking that must be overcome. As Bob Dylan says at the end of his records, good luck to everyone.
Not sure if you are musician but if you were a bass player and had a bass with a funny neck that had one or more dead spots or was missing the low E string, these flaws would be there regardless of what room you played it in. Listen to your loudspeakers outside (an excuse for a bbq) and you hear them without the room progressively containing the bass, so outside it's very thin but good stereo image, usually better than inside.
The emphasis on loudspeaker frequency response is that magnitude uniformity if possible at least at the source is ideal like flat response is elsewhere, an indicator of linearity, no dead notes.
The frequency response is what lets you distinguish a subwoofer from a portable radio before you recognize the song.
How it interacts with the room is effected by the speakers directivity, the more directive, the larger the "near field" area is where the direct sound is significantly louder than the reflected / late sound. The larger the room, the more difficult the room becomes to have a large nearfield. One could very rightly argue it's the response at the listening position, rather than 1m response that matters and that is more tied to directivity not 1m response.
Your descriptive vocabulary is that of reviewers "Air, transparency, richness, naturalness, soundstage dimensionality, coherence, presence, things of that nature." All describe the experience, the impression if you know the hifi terms, but the connection Heyser sought was between the hifi vocabulary of the day like you use and the engineering aspects of the loudspeaker. Remember those terms are mostly from for hire writers trying to capture / sell an impression .
Put your self on the other side off the product lifespan line.
The or at least one of the dilemma the speaker designer is in is that how do you make it sound the best regardless of what or who's music is played? What's the best anyway?
For me, the only blind indicator of anything like being "signal faithful" to any music was the generation loss test. With that you can hear what's wrong as it is exaggerated but it doesn't tell you what to fix.
I know people who's musical taste is shaped by what their speakers can do and that won't do here where i have no idea who will use them..
For speakers closer to the listeners. how do you also make them disappear in the stereo image, so that your not aware of the speakers and the singer is standing concretely sonic ally but invisibly in front of you more "real" than a center channel?
Those are some of the questions i have used Heyser's measurement system to investigate since our lab got one of the first ones in the late 80's
You are hyper focusing on frequency response again. Do you think I fell off a turnip truck yesterday? Regarding Heyser, as my boss at NASA would say, never get behind anyone 100 percent. I suspect trying to analyze speakers or any other audio component involves way to many variables to make generalizations regarding their performance.
Edits: 02/10/23
Hyper focused? Perhaps go back and read what i wrote and try to look at it from an engineering standpoint "as if" you were actually designing and building a new loudspeaker yourself.
How does one convert your reviewers descriptive / subjective vocabulary in to audible reality without real engineering?
Without knowledge of what does what in the design, your effectively left wondering where is the "talent" slider on the mixing board.
"Do you think I fell off a turnip truck yesterday"
Unclear exactly what you mean, are you suggesting a possible injury from a fall?
"Regarding Heyser, as my boss at NASA would say, never get behind anyone 100 percent."
While crediting a deceased audio pioneer isn't a parallel here in my book, two bits i heard making space flight hardware that apply "keep an open mind but not so much your brain falls out" and one that applies to politics as well, "the Vector of change, while less exciting is actually more important than the Magnitude of change".
This conversation can serve no purpose any more. It's a Mexican stand-off.
Yes perhaps, reminds me a little of a reactive circuit with Current and Voltage in that one has the real and imaginary components
More like trying to solve x number of simultaneous equations in x + n unknowns.
Edits: 02/11/23
~!
The Mind has No Firewall~ U.S. Army War College.
Nt
Edits: 02/10/23
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