hpr-knowledge-base/hpr_transcripts/hpr0792.txt

Episode: 792
Title: HPR0792: Binaural Recording
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr0792/hpr0792.mp3
Transcribed: 2025-10-08 02:36:35

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Good morning, good afternoon, good evening. This is Mr. Gadgets and I listened with interest to episode 785 because it's actually reminded me of my roots.
My technology roots and really what got me into computers, which has been my vocation for low these 35, 40 years that I've been actually more like 40 now, that I've been, no, sorry, 35, 35 years that I've been working with computers and making my living with micro computers most of that time.
And in this particular case, it was about my neural recording. Now, I didn't touch the contributor's name. I live in that double feed and I didn't quite catch the same one.
So I'm not going to try to make a bad pronunciation of it here and really murder the pronunciation of the same.
But he was talking about my neural recording. And by now recording is very interesting subject matter, which I read on and off throughout the years. There's actually a very good technical library attached to the Hall family or, you know, the benefactor was a member of the Hall family, Linda Hall.
And I believe if I'm correct, she was married to Donald Hall, I believe it is, anyway, the original founder of all my cards. But anyway, the Linda Hall library is a technical library that's right set down in the middle of the University of Missouri, Kansas City campus.
And I used to go there and look up things, including things about my neural recording. I remember reading this really interesting paper on getting rid of his on paper quarters by this guy named Dolby.
And it's actually the most frustrating thing about the Linda Hall library is this is all very, very early or even pre-micro computers.
And so there was no computerized system to look anything up. It was the old library index card system, the Dewey decimal system.
And I would go and I would find an interesting looking article from some magazine or a very interesting book. And I would either pull it myself from the sax or sometimes the librarian would have to pull it from some special tax.
And lo and behold, it would be in German, which I speak a little bit of singers German, but actually that's the only language I had any formalized study in hitting college.
But my knowledge of German was nowhere near reading a highly technical article. And I found some vinyl recording kinds of articles there.
As this gentleman pointed out, the interesting thing about vinyl recording is it does give you the phase relationships and give you an excellent reproduction of the sound if you are listening on headphones.
Listening on even earbuds, although probably you would need a really good frequency response to really get the effect. So probably a larger set of headphones would be more appropriate, even better if you have a set of cans that was sealed with rubber caps to isolate you from the upside world.
Rather than my preference, which is to have a set of cans that has the phone and allows the outside world sound to get in.
And vinyl recording does maintain phase relationships and the differences in the amount of sound that's reaching each of the two microphones. And you only get the vinyl effect, though, if you are wearing earphones.
We in the recording studio, now this is all pre-digital recording, although that's how I got into computers, as digital audio was coming. And I taught myself everything I could find out about that and definitely learned how to program computers and have made my living ever since.
We had a Reeboks recorder, a shooter, several high-end, reel-to-row recording devices, and our primary set up in our primary hall, that was our recital hall at the Conservatory of Music, had a set up, and we actually used this also, literally, we'd go and record larger concerts in other halls that were available to us.
And it used a matrix microphone, rather than a binaural microphone. Binaural was very interesting because you can get the effect with the two mics mounted in headphones, similar to what that gentleman was describing.
The real serious binaural people even have, like, little kind of imitation heads, kind of like you'd see on CSI if you watch American TV where they had made out of the ballistic gelatin, and they tested to see how they can reproduce the wound or something.
It'd be something similar without, of course, it didn't matter to us how accurate it was in terms of how accurate a wound would be, but you would want to add to, as well as possible, mimic the human skull and the density, but it was most important, the shape of the ears.
And you would actually place the microphones within the fake ears, and then set that in the room where it is you wanted your particular player reference to be for the binaural recording.
Just because the ear itself affects the face relationships and the relative relationships of the amount of sound kidding each microphone.
The matrix recording system did a similar kind of thing and was very, very similar to a binaural recording in terms of when you listen to it with headphones.
You really got the effect of your head was exactly in the position where the two microphones involved with the matrix recording were when they were recording to place.
To the point that in our setup we had an extremely large tripod rolling base of a microphone stand that went up to approximately 10 to 12 feet, and we had a 12 foot boob counterbalance, of course, that rode on the top of that microphone stand.
And so we would suspend the microphone for our concerts that we would record and our titles that we record approximately five feet up those, and about four feet away from the front of whatever stage was involved.
And this minimized the visual impact on the audience just that then like from stand there wasn't a microphone hanging in front of the singer or in front of the piano with the NFS playing or whatever other instrument was involved and gave us a good effect of a mixture of what the room sounded like, the audience as well as picking up the entirety.
And we would use this setup for the full orchestral and concert band kinds of recordings that we would do the full concert choir with 100 some on people didn't edit size the group.
And when you listen to a recording that was made by this matrix microphone with headphones, you were hanging five feet above the head.
So 12 feet at least maybe 14 feet above the floor of the concert hall and you were suspended in mid air your head was actually suspended in mid air.
So it sounded excellent. I mean it gave you all of that effect and you could hear people walking across the stage.
The audience when the applause happened the audience was applauding and they were behind you when you had on heads up.
And of course the performers if we had a small group of jazz trio or something like that you could pick out you could hear exactly where they were in reference to that microphone position.
But the difference with thing that I'm not recording is it is the single and the best single mic position or too much involvement at a single point where those microphones were positioned the best recording that I've ever heard on speakers to give you a similar kind of experience.
It wasn't as direct and as profound as with headphones. So the audience left that you didn't get quite the effect of the audiences behind you quite as much.
But it maintained phase and it maintained the reference points for how loud on each side of the stereo effect that you're trying to go for in a way that I've never heard from any other microphone system.
Now we didn't have advanced electronics to accomplish that but the way the matrix microphone system works is you have a single microphone.
We had an anointment and godly expensive in the middle seventies when I'm talking about none of the cheaper large typhoon by a friend microphone existed that this nowadays they were all extremely expensive and mostly German.
And we had an anointment cardioid microphone that would be positioned so that the cardioid pattern was pointed right to the center of the stage.
So for the solo artist it was right about their head and pointing straight you know well not straight but at an angle down towards them it was a group that was a less oblique angle that was pointed to the back of the conductor's head essentially or just over the back of the conductor's head.
And then there was a figure eight microphone that was placed so the figure eight pattern was perpendicular well parallel to the front of the stage.
In other words the figure eight pattern was picking up a side to side of the figure eight and the cardioid was pointed straight ahead towards the sound source.
We would then take the two signals from those microphones and we ran it through a box that had two matching transformers and the two matching transformers were not doing any kind of impeach from one impeach to another.
They were equal impedance six hundred to six hundred which is typical of professional microphones and it it nearly matrix together the signals from the two microphones.
So essentially it was actually a series of four transformers I believe that was involved or it might have been two with special bindings.
I don't remember exactly but it was the side of the metal box to minimize outside influence on the transformers and what that matrix of transformers did is it took the front microphone the front facing cardioid microphone and it added that that was a part of both the less signal and the right signal.
And then it would take the figure eight microphone signal and in one case that signal was passed in in phase.
So those transformers were wired together so that it was the front facing microphone the cardioid plus the figure eight and that was your left channel.
And then the other channel was the front facing microphone was plus but it the side to side microphone the figure eight microphone was set out of phase.
So we reversed essentially because of balance microphones if you're an audio person you know what I mean by that and we took the balance and we just reversed it so it was out of phase.
And what that did and the mathematics are very complex here but by doing that you literally got your left and right signal from two microphones that were right next to one another.
There's no X, Y, 22 different directions here. There actually is one microphone with the side to side figure eight and one microphone pointing straight ahead.
They're pointed on a custom made microphone clip that would hold them in the proper positions.
You always had to have the figure eight microphone positioned in such a way that the front was always to the left because that's how you would get your left.
And the rear was pointed to the right and then when you plugged them in the right way into the matrix spot it would come out stereo on the other side.
Point plug it into the stutter or the revox depending on what kind of recorder we were using for this particular gig.
And we got a stereo sound out of that that I have not been reproduced by any pair of microphones.
Getting involved, it was all analog, there was no digital processing here of course.
But even to this day I don't know even in this day of much cheaper large-difit microphones than I am amazed at how good some of the extremely inexpensive microphones nowadays sound especially compared to the thousands of dollars that that type of microphone used to cost when I initially got into this whole recording booth.
If you're interested in playing around with this idea there is actually a company that I remember from those days that is still in this and the company was called PAIA.
You can still look up PAIA in the Google. You can Google PAIA, Google it's both a noun and a verb.
And you can Google PAIA, they still have a catalog. One of my best friends from college actually put together a equivalent of a MOOC synthesizer, or at least the poor band equivalent of a MOOC synthesizer, way back when from kits from PAIA, they still have a few kits that have to do with metalized synthesis.
So if you're a real sucker for that analog sound, there are still some nice kits that they have available that are along the lines of that PAIA catalog kits that are still available.
So one of the things they have is a little matrix microphone that you can build yourself that has an electronic circuit that will pay two electric condensers, which is what the other gentleman was talking about for his final and go back and listen to that if you're interested in experimenting with stereo mic because his technique of finding a matched pair of microphones is really, really important in this whole process.
So in fact, PAIA has done that. It has matched the three microphone capsules. So they'll give you three microphone capsules that are matched as far as the output with the equivalent inputs of sound pressure.
And it has a box that comes with it where you can mount those three one, of course, facing forward and one facing either direction. And then it has an electronic circuit because those aren't really balanced.
And it's not as easy even if you have the transformers to do the little matrix box trick. They aren't balanced microphones. And so it would be more complex to accomplish that task.
And they have a electronic circuit that does that matrix thing for you. And you could experiment around with this whole matrix microphone concept.
I don't know of anybody who is making a figure eight microphone that is as inexpensive as some of the regular large diaphragms that are available.
But as you might be able to tell, it's a point of interest with me, microphone techniques. If still something I pursue, even though I have not made my living through sound reproduction or recording low these nittyy years, but I still have an interest in it.
And since a lot of people who are listening to HDR are also involved as musicians or at least in recording a podcast and things like that.
I thought you might be interested in another microphone method, this matrix microphone method. I didn't look up on Wikipedia to see if there's any kind of entry about it.
I'm not sure exactly where my boss at the time in the recording studio got the information on building this, but he had picked it up in some technical journal of the time as a method it was quite expensive in terms of the microphones involved.
But as I say, it gave us some superb result for stereo recording both in and this is mostly live recording. This is all Billy live recording. There was no laying down tracks and then adding tracks to them.
Unless, of course, you talked about our recording of the MOOC synthesizer that was in the lab in the Ruffles Stover Building, the RS Building, which was the old Stover Mansion, Russell Stover Candies Headquarters here in Kansas City, and the old RS Mansion was a building that was adjacent to the main music school building.
And up in the high raptor, you know, third floor of the mansion was our electronic music lab that had a huge MOOC synthesizer that was at least six feet tall and anywhere from 10 to 12 feet wide.
That was not very portable, of course. And so anything that we did with electronic music was done with multi-channel recording and laying down tracks because, of course, that MOOC synthesizer didn't have the ability to do, you know, multiple notes at a time, right?
Only one note at a time and all analog for the synthesis of the notes as well as all the filtering and other kinds of effects that could be placed on it.
So, there's a little for right into, you know, my past and the history of recording as all of the matrix microphone technique.
My boss at the time with a guy named Jim Russell, I'm still in periodic email contact with Jim, and occasionally I give an email from him about one or the other technical kind of issue.
And Jim's favorite thing, and then I'll leave you to go. One of the things from back then was making your own speaker systems.
A lot of people who had stereo, you know, setups wanted to save the money, you know, students, especially would want to save money. Music students didn't exactly have all the stretch in the world.
And so one of the ways you could save money on your speaker system was to build it yourself.
And in fact, one of the major players that you would buy components to build your speaker systems was a place called McGee Radio here in Kansas City.
Most of, if not, I would say probably way over half, maybe even 70% of the build your own speaker articles, which would happen lots and lots in magazines of the time, would say at the conclusion of the article components for this, you know, speaker article are available from McGee Radio.
So 17th and McGee, 17th sets and sets for G, can't sit misery. I think it's 17th, might be 18th.
Anyway, building's still there, but of course, McGee Radio has gone by the wayside, but build your own speakers was a big thing at the time.
And one of Jim's favorite phrases about people who built their own speaker systems was, and I quote, they don't know what they want when they start and they don't know they haven't got it when they're finished.
So anyway, hope that your audio adventures are interesting. And since we did have a plea for people to call in the summer and fill up the coffers with extra small episodes, maybe a little short episodes.
Do you have something on the audio wise? Did you build your own speakers at the back of the 70s or 80s? What was your first sound system like?
How did you get interested in audio? How did you get interested in computers, of course, and make your way to Linux? All those kinds of topics here. Are you sick and tired?
Are you sick and tired of hearing Mr. Gadget throw on and on and chili frosts and falls over backwards? Call in your own episode or better yet. Use your microphone and record it.
All right, this is Mr. Gadget out here. Get ready to record something else and I'll talk to you later. Bye.
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