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24.21.8.3
In Reply to: RE: August Stereophile Amplifier Measurements - an observation, or two. posted by John Atkinson on July 14, 2014 at 16:24:21
John, would you be willing to share with us what you to prepare your measuring instruments for a measuring session?
Who are the mfg'ers and what models do you use and what is their age?
Are your measuring instruments recalibrated from time to time?
Also, do you do any special prep for the component or speaker about to be measured?
Thanks,
Follow Ups:
> John, would you be willing to share with us what you to prepare your
> measuring instruments for a measuring session?
A couple of hours' warm-up of both test systems and DUTs, to ensure that
all are stable. With electronics, experiments with grounding between DUT
and test system to get the noise floor as low as possible.> Who are the mfg'ers and what models do you use...
I mention these in every review. Measurements of amplifiers and digital
products are currently performed with my top-of-the-line Audio Precision
SYS2722 system. For some tests, and to check the results of others with a
different measurement system, I use my vintage Audio Precision System One
DSP and a 1999-vintage PrismSound DScope 2 with an Ayre QA-9 A/D
converter. Other products include a Fluke 87 digital multimeter, Kenwood
and Hitachi analog oscilloscopes, an 8-bit Heath digital oscilloscope,
Heath oscilloscope calibrator, and a Neutrik Minirator signal generator.
For loudspeakers, I use DRA Labs MLSSA system and SMUGSoftware's
FuzzMeasure 3.0 programs, with calibrated DPA 4006, Earthworks QTC-40,
and Mitey Mike II microphones, Earthworks and Metric Halo microphone
preamplifiers, and an Outline speaker turntable.> And what is their age?
The AP System One dates from the early 1990s, the SYS2722 from 2007, the
MLSSA system from the late 1990s. The microphones range in age from 1989
to 2006.> Are your measuring instruments recalibrated from time to time?
The System One is no longer supported by AP; the SYS2722 was last
calibrated 3 years ago and is due for recalibration. At the start of
every speaker measuring session, I measure the tweeter-axis response of
a 1978 LS3/5a and compare that with the earlier responses of the same
speaker. On a less regular basis, I compare the response taken with each
of my 3 measurement microphones with those taken with the others and to
check MLSSA, I repeat the response measurement with different hardware:
Fuzzmeasure on my laptop and a Metric Halo Firewire A/D.
John Atkinson
Editor, Stereophile
Edits: 07/18/14
Thanks for the info, John. Good stuff.
On another note, I remember you stating in I think the Sept, 2009 issue when a group of you were doing some comparisons between live piano and that same piano played back via a recording of that live session, that even though you heard some good qualities in the playback, it was your opinion that much of the live music being recorded never made it to the recording medium. (I'm paraphrasing of course.)
But I don't recall your elaborating on that point.
Anyway, is that still your take today?
Thanks,
> Thanks for the info, John. Good stuff.
You're welcome.
> I remember you stating in I think the Sept, 2009 issue when a group of you
> were doing some comparisons between live piano and that same piano played
> back via a recording of that live session, that even though you heard some
> good qualities in the playback, it was your opinion that much of the live
> music being recorded never made it to the recording medium. (I'm
> paraphrasing of course.)
> But I don't recall your elaborating on that point.
I summed up my opinion at the article page linked below.
John Atkinson
Editor, Stereophile
Thanks, John. You call that a summation? :)
Nice writing style, John, and very provocative too. You’re obviously quite deep, thorough, and well-informed. I admit that I have yet to finish reading the entire dissertation.
You bring up some very good points throughout. Too many to list actually for my limited short-term memory to recall. You dive into levels few consider, including the internal modeling, etc.
Nevertheless, there are a few points that stood out in your writings. But have you considered the possibility that:
1. Just because you dive deeper than the average bear and because you’re a thinker and a sound engineer and an editor-in-chief of a popular magazine should never automatically imply that you’re postulates are correct. Nor should one automatically assume they are wrong either. For example, you postulate that inner modelings have occurred in the listener whereas this cannot be proven right or wrong. Or that you yourself have your own inner modeling occurring that may lead you to incorrect assumptions.
2. Like any subject, one can go as deep as they want and loose many along the way. Especially when so many struggle with just the fundamentals back at the surface.
3. That in your quest to dive deep, you yourself are in uncharted territory, and in the end could be as far or maybe even further off the mark than those who remain at the surface? For example, when a gent like yourself pulls back the covers on a given topic, you are in uncharted territory and you open up a slew of new variable to consider, including those that you mention as well as those you may have overlooked including some-to-many traced all the way back to the surface.
For example, if we go back to my first question to you about your sensitive measuring instruments. You mentioned how some of your equipment was antiquated, out of production, no longer calibrated, etc. Those are potential shortcomings to others and should raise questions for those who put stock into your published measurements. Additionally, what are your thoughts about sensitive measuring instruments unable to discern differences that a well-trained ear can?
But more importantly, in your response about your sensitive measuring instruments, you neglected to mention taking any precautions whatsoever regarding the possibility of minimizing the affects of noisy AC or under controlled vibrations having potentially any effect on your resulting measurements. Nor do you make mention of what platform you use to place the component under review on nor do you mention the platform upon which your sensitive measuring instruments are placed. For example, are you using a kitchen table, an antique coffee table, a sophisticated bench, etc, and do you use the same platforms for every test made?
Another point worth mentioning is that to the best of my knowledge you’ve yet to mention the potentially inferior hearing abilities of at least a few of your esteemed colleagues. Surely, like some of us, you’ve encountered such types who quite frankly couldn't punch their way out of a music bag if their lives depended on it. Such types would potentially and significantly skew the results of any listening tests of any type.
Also, regardless of the playback system, what if in all of your endeavors you are only be hearing a small percentage of all the music information that is embedded in a recording, all of which may be processed, yet the vast majority remains inaudible due to a very high noise floor inherent in every playback system.
For example, as mentioned earlier, you stated in the Sept. 2009 issue regarding the live piano vs recorded that you speculated much of the live music never reached the recording. Moreover, Robert Harley of TAS stated in the Mar/Apr 2009 issue that he speculated that something catastrophic was occurring at the recording mic’s diaphragms so that much of the music never made it to the recording. Harley reported elsewhere that he arrived at this conclusion based on a rather simple test performed by Ed Meitner, hence we can probably assume Meitner also arrived at a similar conclusion. Then there's Jonathan Valin of TAS stated in circa 2007, “We are lucky if even our very best playback systems are able to capture even 15% of the magic of the live performance.” To Valin’s point I know a few who said even that 15% is being optimistic.
Hence, I ask, in all of your research, listening tests, and studies and postulations about hearing and listening and interpreting, what if you discovered that what we hear from a given playback system has been based on your (and everybody else) hearing perhaps only 1/3rd of all the music info embedded in a given recording, regardless of format?
Since to some exent you seem to have already admitted to this serious deficiency, as have some of your colleagues, how does that factor into your postulations?
I'd be interested to hear your thoughts.
Thanks,
On the MOMENTUM preamp...That looks like a "gear" operating the volume control/meter contraption,,,,
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