I once (1983) put a clay flower pot (roughly a 7 inch diameter which tapered toward the bottom) on my coffee table (probably on a folded towel or ? to reduce table bounce acoustics), put an omni-directional Radio Shack electret condenser mic on each side of the pot, such that the diaphrams would be about where an ear would be if the pot was a head, aimed the mics slightly outward - a relatively sloppy setup, then hit the record button on a little cassette recorder, grabbed my acoustic guitar and played it a bit.
When I played it back through headphones, before the guitar part even started, the rustling noise from me grabbing for the guitar sounded so real that I jumped up and took off the phones, thinking someone else was in my house, before I had a chance to think... the realism was astounding.
I've always meant to explore that further, but after learning about interaural crosstalk with speakers I never really got back to it. Now that so many people listen to music thru headphones with their smartphone, binaural recordings may come back. Those smartphones could soon be doing stereographic video, to be played back with a visor display device (separate display for each eye). Combining stereo graphic visual with binaural audio reproduction sounds juicy to me.
But I want to agree with someone above who feels that you don't need to have an imitation silicone rubber ear with a canal and mic diaphram right where the ear drum would be, digital EQ and etc. The ear drum has radically different EQ than a mic, in order to compensate for the acoustic effects of an ear canal and pinea. Getting all of that just right may give a slightly better result, but I wouldn't expect much difference. My sloppy set up worked incredibly well.
Linkwitz (who's very well educated and picky) did a bunch of binaural recordings by attaching tiny electret pics to the rims of his glasses, and you can buy those recordings from him. I haven't, but just that he is offering the CD's of his recordings for sale tells me he thinks that method works very well. You can learn all about it on his website linkwitzlab.com.
I can't help thinking that the protruding curvature of the flower pot between the two mics contributed significantly to the realism effect, but I haven't done any other research on this personally. Linkwitz's method didn't really have that, since the mics were at the front of his glasses, by his eyes, rather than back where his ears were.
So my feeling is that this does not need to be complicated or expensive to work very well.
When I played it back through headphones, before the guitar part even started, the rustling noise from me grabbing for the guitar sounded so real that I jumped up and took off the phones, thinking someone else was in my house, before I had a chance to think... the realism was astounding.
I've always meant to explore that further, but after learning about interaural crosstalk with speakers I never really got back to it. Now that so many people listen to music thru headphones with their smartphone, binaural recordings may come back. Those smartphones could soon be doing stereographic video, to be played back with a visor display device (separate display for each eye). Combining stereo graphic visual with binaural audio reproduction sounds juicy to me.
But I want to agree with someone above who feels that you don't need to have an imitation silicone rubber ear with a canal and mic diaphram right where the ear drum would be, digital EQ and etc. The ear drum has radically different EQ than a mic, in order to compensate for the acoustic effects of an ear canal and pinea. Getting all of that just right may give a slightly better result, but I wouldn't expect much difference. My sloppy set up worked incredibly well.
Linkwitz (who's very well educated and picky) did a bunch of binaural recordings by attaching tiny electret pics to the rims of his glasses, and you can buy those recordings from him. I haven't, but just that he is offering the CD's of his recordings for sale tells me he thinks that method works very well. You can learn all about it on his website linkwitzlab.com.
I can't help thinking that the protruding curvature of the flower pot between the two mics contributed significantly to the realism effect, but I haven't done any other research on this personally. Linkwitz's method didn't really have that, since the mics were at the front of his glasses, by his eyes, rather than back where his ears were.
So my feeling is that this does not need to be complicated or expensive to work very well.
Ooops, I was wrong about how Linkwitz did his binaural mic setup. The mics are actually back by his ears. Sorry about that. Maybe it was the other way originally. Here's the link:
Sound Picture CD
Sound Picture CD
@Bob
Some people need more or less realistic acoustical cues to recreate the event in their brain.
I'm sure your flower pot microphone can get very good results in certain situations.
The interesting test to do would be to compare it with binaural recordings of the same event.
I myself have built something similar to your microphone, which is my take on the jecklin disk spaced pair.
I used a 6 inch diameter dodge ball to mimic the shadowing effect of the head with omnidirectional microphones attached to it where the ears would be.
I have gotten very good results with it, when the event recorded is mostly in front.
Here is an example. https://www.youtube.com/watch?v=p5JdrBTiaHQ
If I had to rank the microphones I built and tested in terms of localization capability, I would put the dodge ball microphone at the bottom, then mannequin head with just pinnae, then pinnae+plastic tube and finally the anatomically accurate ear+canal.
All of them need to be equalized, even the dodge ball.
Also, the recordings sound closer to the real event in terms of individual instruments sound characteristics as we progress in the same order as above (provided that equalization is used).
It might be interesting that I think the difference between dodgeball and just pinnae is less than the one from just pinnae and pinnae+plastic tube. Which to me confirms the importance of having some kind of ear canal replica other than just the pinna.
I wouldn't get the speaker's cross talk issue prevent me from exploring binaural recordings anyway.
While it is true that binaural is ideally played through headphones to bypass the issue, the level of realism achievable through regular speakers playback is still very good and definitely much better than any other kind of recording technique out there.
Chesky has an entire line of recordings made with binaural microphones. While they rightly invite the listeners to use headphones, you can try those recordings with regular speakers and get an idea for what is possible to achieve.
I am a lover of stereoscopy (did you see Brian May's owl stereoscope?) and stereographic videos look very interesting to me too. I see that as the equivalent of binaural for sight.
As far as this not needing to be complicated, it all depends on how handy one is. Binaural microphones are not that hard to build, and the dodge ball one is even less difficult.
As per the price, one can build a pinna+plastic tube binaural microphone for as little as around $200-300 in material.
My dodgeball was about $150 when everything was said and done.
We are not talking retail prices for a Naumann KU 100 or a Schoeps KFM 6 (the equivalent of the dodge ball microphone).
@turk
That's a very good point.
Fletcher/Munson curves are luckily pretty similar in the SPL range of normal listening sessions. They look like almost translated up and down, so that helps.
I see more and more recording engineers out there advocating for mixing sessions based on realistic SPL levels of the sound being mixed. and that is encouraging to me.
Like everything else, binaural recordings can get us only close to the real experience, and I spent quite some time, energy and money to get as close as possible.
Human hearing is incredibly complex. Some people need visual cues to localize sound, for example.
That being said, as of now, binaural with the correct equalization is the closest to the real thing one can get, as far as 360 deg soundstage and realistic reproduction of the sound of instruments+venue event.
Some people need more or less realistic acoustical cues to recreate the event in their brain.
I'm sure your flower pot microphone can get very good results in certain situations.
The interesting test to do would be to compare it with binaural recordings of the same event.
I myself have built something similar to your microphone, which is my take on the jecklin disk spaced pair.
I used a 6 inch diameter dodge ball to mimic the shadowing effect of the head with omnidirectional microphones attached to it where the ears would be.
I have gotten very good results with it, when the event recorded is mostly in front.
Here is an example. https://www.youtube.com/watch?v=p5JdrBTiaHQ
If I had to rank the microphones I built and tested in terms of localization capability, I would put the dodge ball microphone at the bottom, then mannequin head with just pinnae, then pinnae+plastic tube and finally the anatomically accurate ear+canal.
All of them need to be equalized, even the dodge ball.
Also, the recordings sound closer to the real event in terms of individual instruments sound characteristics as we progress in the same order as above (provided that equalization is used).
It might be interesting that I think the difference between dodgeball and just pinnae is less than the one from just pinnae and pinnae+plastic tube. Which to me confirms the importance of having some kind of ear canal replica other than just the pinna.
I wouldn't get the speaker's cross talk issue prevent me from exploring binaural recordings anyway.
While it is true that binaural is ideally played through headphones to bypass the issue, the level of realism achievable through regular speakers playback is still very good and definitely much better than any other kind of recording technique out there.
Chesky has an entire line of recordings made with binaural microphones. While they rightly invite the listeners to use headphones, you can try those recordings with regular speakers and get an idea for what is possible to achieve.
I am a lover of stereoscopy (did you see Brian May's owl stereoscope?) and stereographic videos look very interesting to me too. I see that as the equivalent of binaural for sight.
As far as this not needing to be complicated, it all depends on how handy one is. Binaural microphones are not that hard to build, and the dodge ball one is even less difficult.
As per the price, one can build a pinna+plastic tube binaural microphone for as little as around $200-300 in material.
My dodgeball was about $150 when everything was said and done.
We are not talking retail prices for a Naumann KU 100 or a Schoeps KFM 6 (the equivalent of the dodge ball microphone).
@turk
That's a very good point.
Fletcher/Munson curves are luckily pretty similar in the SPL range of normal listening sessions. They look like almost translated up and down, so that helps.
I see more and more recording engineers out there advocating for mixing sessions based on realistic SPL levels of the sound being mixed. and that is encouraging to me.
Like everything else, binaural recordings can get us only close to the real experience, and I spent quite some time, energy and money to get as close as possible.
Human hearing is incredibly complex. Some people need visual cues to localize sound, for example.
That being said, as of now, binaural with the correct equalization is the closest to the real thing one can get, as far as 360 deg soundstage and realistic reproduction of the sound of instruments+venue event.
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well after several go's at it i dumped the idea of using an omni type capsule for binaural applications especially with respect to mounting them in a tube (why start with omni when your going to stick it in a tube and limit it's angle of reception/capture?) and after struggling with equalization routines to compensate for all the non linear behaviour of the pinnea replica's and styrofoam heads i settled on the technique i described earlier in the thread as being the easiest to replicate with consistent results with minimum compression or wild eq routines.
take a look at some of the Zoom field recorders i did a few location recordings with an H6 after using that i can't think of reason i would want to freak people out with a "dummy" head!
take a look at some of the Zoom field recorders i did a few location recordings with an H6 after using that i can't think of reason i would want to freak people out with a "dummy" head!
Binaural microphones are definitely obtrusive. There's no question about that.
That's the reason why I ended up building the dodge ball microphone.
It is a little easier on the eye when people really can't get past the head.
I'm surprised you struggled with microphone equalization. Logic Pro with MatchEQ works very good.
The reason for omnidirectional capsules is the more linear frequency response compared to directional ones.
Also, directionality in capsules is achieved through capsule mount geometry and cancellation through internal sound reflection.
This adds unwanted resonances, and I must say I don't like directional microphones even when not mounted in a ear canal.
Directional capsules also suffer from the proximity effect. I don't know if one can talk about proximity effect when mounted in a tube, but I didn't want to find out myself when an omnidirectional capsule can be used instead, with better frequency response and no resonances on top of that.
That's the reason why I ended up building the dodge ball microphone.
It is a little easier on the eye when people really can't get past the head.
I'm surprised you struggled with microphone equalization. Logic Pro with MatchEQ works very good.
The reason for omnidirectional capsules is the more linear frequency response compared to directional ones.
Also, directionality in capsules is achieved through capsule mount geometry and cancellation through internal sound reflection.
This adds unwanted resonances, and I must say I don't like directional microphones even when not mounted in a ear canal.
Directional capsules also suffer from the proximity effect. I don't know if one can talk about proximity effect when mounted in a tube, but I didn't want to find out myself when an omnidirectional capsule can be used instead, with better frequency response and no resonances on top of that.
It comes from looking at frequency response charts. Omnidirectional ones have flatter responses, generally. Plus there is the resonance issue.
MatchEQ is very easy to use.
You load the template, record, then compare.
I use white noise as template file, play it through full range speakers, record and then compare. It works quite good and it is very reliable as a method.
MatchEQ is very easy to use.
You load the template, record, then compare.
I use white noise as template file, play it through full range speakers, record and then compare. It works quite good and it is very reliable as a method.
Thanks for sharing. I hadn't thought of using a dodge ball. I imagine that could work fairly well. I've been tempted to get an 8 inch diameter plexiglas tube, mount it vertically, maybe 10 inches high, and put omnis on each side facing forward. I've also pondered the idea of using that for frequencies above about 800HZ, and using boundary mics or regular omnis spaced way far apart for frequencies below 800HZ. It would be interesting to try anyway.
The Youtube recording sounded excellent to me (through headphones). I wish there had been other sounds or instruments in the room for more imaging info, but the acoustic reflections of the room may have added significantly to the sense of being there.
that means that your full range speakers are +/- 3 db right across a 20 to 20k bandwidth and can be recorded with no room mode contributions....
and compare to what? what are you referencing?
The template of white noise looks like a flat frequency response.
Assuming that the speakers are capable of playing the white noise back, the signal recorded is the frequency response of the binaural microphone (the HRTF).
Compare the HRTF to the flat response and you have the correction filter.
The +/- 3 db is a big assumption. Let's just say that this is another thing where you can only get somewhat close to ideal.
However, acoustic cues at the extremes of the spectrum are not the primary ones that the brain needs for localization, nor the ones where most of the musical content resides, so a less than ideal speaker can also be used with virtually same results.
Assuming that the speakers are capable of playing the white noise back, the signal recorded is the frequency response of the binaural microphone (the HRTF).
Compare the HRTF to the flat response and you have the correction filter.
The +/- 3 db is a big assumption. Let's just say that this is another thing where you can only get somewhat close to ideal.
However, acoustic cues at the extremes of the spectrum are not the primary ones that the brain needs for localization, nor the ones where most of the musical content resides, so a less than ideal speaker can also be used with virtually same results.
If you mount a cardioid capsule in a tube you are blocking the rear vents turning it into an omnidirectional capsule.
Same thing happens when you hold a vocal mic (SM58) like a rapper thus blocking the vents. This turns the mic into an omni with predictable consequences: The proximity effect disappears and feedback will be an ever-present problem.
It is equivalent to some loudspeakers: A cardioid mic works like an open baffle to limit directivity by cancellation.
A shotgun mic uses the tube to limit directivity like a horn by limiting the entry/exit angles.
If you use a Zoom field recorder you get a stereo recording unless you separate l&R acoustically with an at least head-sized plate but not a binaural one which in context of this thread seems pointless.
Btw there is some eq software which linearises the output of headphones.
Itself a misguided endeavour since it appears the makers believe wrongly that a flat FR would be desirable for 'phones in general however it would optimise headphones for binaural recordings.
i wouldn't mount a cardiod in a tube nor do i suggest it anywhere.
in a live performance situation this would happen but we aren't sending the signal to a monitor nor are we cupping the mike element with a hand or fake ear.
that's the reason i use cardoid they have rejection from the rear. it's a closer analog to a "single ear"
shotgun mic's use several tubes to accomplish their ability to capture at a distance but are also frequency limited to voice band
i would rather have a good stereo recording than a bad binaural one. and the point there was the "freak" factor of the dummy head vs a piece of tech that gets most of the way there.
one of the other things about binaural recordings is the attempt to achieve complete seperation between left/right when in fact our ear/brain uses input from both simultaneously.
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