Thursday, May 3, 2012

Visit by Stan Ricker

A friend of George's brought world renowned audio engineer Stan Ricker over for some audio listening and testing on Wednesday afternoon.  It was very interesting hearing his observations and stories.  I wish I had realized that Stan was or may have been the mastering engineer for several of my favorite recordings.  For many years, he produced the Mobile Fidelity Sound Lab special audiophile releases of major label recodings.  According to the web, he was mainly involved with mastering the LP versions.  He might have known something about the CD versions also, one of my favorite CD's is the MFSL version gold disc version of Pink Floyd Meddle.

Like George, Stan is very interested in preserving the correct audio polarity for musical playback.  However his experience and ideas wrt polarity differ in some ways.

Like me, Stan does not believe polarity is consistently audible.  To ensure he gets polarity and other things correct, his mastering system includes an oscilloscope, and he checks waveforms visually.  I also like to use oscilloscopes for various kinds of testing, and have owned and used oscilloscopes since the mid 1970's.  George doesn't own and has only seen oscilloscope renderings on rare occasions, and believes that polarity is so audible that no such tools are necessary.  I don't believe that is true, and it has not been true for me.  Research published in the Journal of the Audio Engineering Society (JAES) suggests that playback polarity is not easy to hear, can only be heard for test signals or solo brass recordings, and even then is much harder to hear on speakers than headphones.  In a real accoustic space, the JAES engineers opined, sound reflections mask the initial polarity.  With real music, the soundfield is too complex for the human brain to sort out correct polarity.  My experience is more in line with the JAES engineers.

Stan knows what the initial impulse of many instruments looks like on the oscilloscope.  Trumpets and drums are particularly good ones to check.

Stan also commented wrt the recording of a Piano.  He likes to record grand pianos with the top removed, because the top causes out-of-phase reflections for a nearby recording mike.  He records above the piano because the hammers underneath the strings drive both string and soundboard upward for a positive initial pulse, which is most similar to what people hear from live piano.  Underneath the piano, the inital pulse is negative, which sounds wrong.  With upright pianos, the situation is different, he records those from the back because the hammers are in front pushing back.

Stan made (or knew of) one recording using a ribbon microphone with some instruments in front and a few in back.  That was the best we to get all the musicians as close as possible to the microphone for the most intimate sound.  Of course that meant that the instruments on the back side of the microphone would not be recorded in the correct polarity.  But Stan argued that the woodwind instruments on the back side did not produce consistent polarity anyway.  He said every other note would be in a different polarity.  I interpreted this as meaning that the same note played twice would not necessarily have the same polarity, there was randomness involved, and Ricker's approach sounded like an acceptable compromise to me.  To George, it was sacrilege, the correct polarity must alway be preserved in recording.  And I found out later that George interpreted Ricker's remarks differently.  He interpreted it as meaning the same note (same frequency) played twice would have the same polarity, but different notes on the scale would be different.  I conceded that if that interpretation were correct, Ricker's method would introduce a potentially audible error, but I still felt it might not be important compared with other factors, so artistic license with respect to was acceptible.  George agrees that people can mess with polarity to achieve particular affects, and that is a subjective and artistic matter, but he doesn't like such recordings, preferring always the correct reproduction of polarity.

Stan said it was also easy to see the correct polarity on recorded LP's with a microscope, and he checked that.

Stan also believed it was best to play mono records in "true mono", using a mono cartridge or summing the audible signals electronically before they reach the speakers.  George said he preferred stereo playback because it puts the groove noise at the speakers but the music in the center, making it easier to hear all the music.  I tend to agree on George with this one.  Ricker said that such playback would introduce all sorts of spurious resonances from unwanted vertical movement into the L-R, causing center image wander and drift.

Stan heard excess highs from the left channel of George's stereo, which has the speaker right against the left wall.  George says he hears no channel imbalance or high frequency reflections, and thinks many people simply image such a defect because of simply seeing the wall.

Overall, Stan seemed to like George's stereo, and spent 3 hours listening to many recodings, including a few of his recent productions which haven't been released yet.  George commented on the polarity he heard in those recordings and the others.  Almost always there was agreement wrt the polarity.  George's friend has generally only spent a few minutes at any visit, claiming he doesn't hear a good center image.  George also specifically demonstrated his newest CD dampers, and showed all the tweaks installed in his system.

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