Author Topic: Parabolic binaural technique by newbie. (Read 5120 times)

yeshe · « **on:** May 22, 2006, 04:02:25 PM »

Hi i am obviously new and I obviously need advice, so sorry if this is a really dumb question.

You can listen to my recordings at www.padmasoundsystem.com although I have not yet used the new mic technique I am asking about, I will this Wednesday the 23rd.

For the recordings at my website I am recording into a Microtrack 24/96 with either the mic provided by M Audio (earliest and May 17 recordings) or two small omnidirectional mics given me by a friend who is a member here and turned me onto this site, (and these files are noted as binaural recordings at my site).

My group has voices, cello, harmonium and percussion. I want to create binaural recordings but have very different recording requirements to pick up the voices as opposed to the drums and cello. The recordings thus far are often dominated by the drums and cello, sometimes losing some of the harmonic subtlety of the voices.

I came up with the idea of creating a parabolic disc for picking up and amplifying the harmonics of the voices and placing the other omni mic at the back end of the parabolic disc so they are separated by approx. 10 inches.

So using my dog's plastic collar I bought last year to keep him from licking a wound, and configuring various plastic plumbing parts to create a nice handle that fits snugly into my mic stand mic holder, I now have a 20" parabolic disc with a 5" plastic plumbing nipple/mic holder in the middle of the disc where wires can go through. I read an academic paper on parabolic mic techniques that said the mic should be placed on the central mic holder at 1/4 of the diameter of the disc from the disc's center to capture the focal point, hence the 5" nipple and the mic pointing back towards the disc.

I plan to place the mics in the center of the room with the group arrayed around it. I intend to aim the disc at the voices and have the cello and percussion opposite being picked up by the omni at the back. I think the parabolic disc acts as a J disc between the two omnis to create the binaural recording.

Any advice?

Yeshe Dorje

padmasound@cox.net

balou2 · « **Reply #1 on:** May 22, 2006, 04:10:11 PM »

I'd LOVE to see photos of this set-up when you do it.

I think you're going to run in to problems with this. Parabolic wave capture is a pretty exact process. You need to calculate distances derivative to frequency and wave size (decibals) or you're going to get a "funneled" sound. At first read, I have no ideas, other than to think the parabolic plastic piece you're describing might be to slim. A larger, shallower piece might prevent the "funnel" sound.

Post your results...I'm interested to hear it.

yeshe · « **Reply #2 on:** May 22, 2006, 06:02:56 PM »

balou2 · « **Reply #3 on:** May 22, 2006, 06:42:59 PM »

Hmmm...I'm curious about this.

First thought = reverb. It's only a small distance, but you could get minimal delay reverb on the back side. What polar patter is the mic?

I think this will only work if you're up close. By the look of the shape, which is not a true parabola, 6' away would be what I'm thinking. I'd be curious to hear the difference in sound if this were a true parabola, with a flat-rounded trough, and not the raised bushing piece that is evident.

Nevermind...just read they're omnis.

You mention the harmonics of the voices, and amplifying them. I'm not sure I understand the term "amplifying the harmonics". Do you mean amplifying the harmonies of a a multi-voice combo? Harmonics refers to the physical characteristics of the voices. Regardless, placing the percussion and cello out of the "parabolic" expansion will definitely increase the depth of resonance you get from the other voices, but will also alter the waves from the cello percussion, possibly even muddy the sound (or rather, baffle it).

Nonetheless, for what you're doing, this might just work. I'm really curious! and +t for the cool invention.

yeshe · « **Reply #4 on:** May 22, 2006, 06:48:45 PM »

So I have put up the photos and also made a test recording and posted it at my website

http://www.padmasoundsystem.com/mp3-sound-healing-downloads/ padma parabolic test#1

I take the whole stand and rotate it 360 degrees on a windy day (sorry)

As forthe voices we sing with vocal overtones so the ideais that the parabolic will be quite nice for the higher frequencies.

the front is placed six feet in front of the voices and the back points to the percussion and cello about ten feet away. Of course both mics pick up the room sound but the idea is that the parabolic binaural will help to create a more "you are there" feel with increased separation of instruments and voices.

bdasilva · « **Reply #5 on:** May 22, 2006, 07:07:28 PM »

Might be one of those see if it works... see if you like what you get.
I have a 32" Clark Parabola that i use for bird sounds... higher frequencies (birdsongs) are collected and amplified 60db... It is very directional. I'm using a AT-3032 omni mic with it.
We "focus" it by pointing it to the sun and using a piece of paper (never you mics)... we figure out where the optical focus is and set the mic elements there.
What you end up with might be stereo but it will not be binaural. That refers to mics seperated by a heads worth of mass... creating a sonic shadow on each side that our ears can hear and pick up the clues that we need to figure placment and source of sound.
Good luck with the project

yeshe · « **Reply #6 on:** May 22, 2006, 07:12:49 PM »

Actually I would dispute the point about not binaural, as what you need to create a binaural recording is a baffle or j disc between spaced mics.

Ideally you put them a head's width apart but it you listen to the test recording I created you'll hear that it is truly binaural.

bdasilva · « **Reply #7 on:** May 22, 2006, 07:14:56 PM »

There IS no baffle... your recording is Stereo

poorlyconditioned · « **Reply #8 on:** May 22, 2006, 07:18:42 PM »

Quote from: yeshe on May 22, 2006, 07:12:49 PM

Actually I would dispute the point about not binaural, as what you need to create a binaural recording is a baffle or j disc between spaced mics.

Ideally you put them a head's width apart but it you listen to the test recording I created you'll hear that it is truly binaural.

+++++++T for the crazy use of found objects. Keep up the good work!

Richard

KLowe · « **Reply #9 on:** May 22, 2006, 07:26:49 PM »

+T's for the best use of a dog E'collar I have ever seen (I'm a vet).

This rules Ts for you.

yeshe · « **Reply #10 on:** May 22, 2006, 09:37:02 PM »

Hi again Bdasilva

If you look you'll see thatthee mics are separated by the parabolic cone. The parabolic cone, dog collar, acts as the baffle. I may be missing somethting and defer to your experience but in reading about binaural technique you put something between the left and right mics. In this case it is a parabolic cone. One emic is in the cone th other is a head's width ditance away out the cak of the mic holder.

yeshe · « **Reply #11 on:** May 26, 2006, 01:29:23 PM »

In case anyone is still interested I have posted the recordings using the dual omni parabolic. One omni mic pointed at the parabolic and one out the back end. I actually covered both sides of the cone with fake fur after getting feedback from a taperssection member. I pointed the back end at the drums and cello at about 8 - 10 feet and the front parabolic mic at the voices at about 6 feet. I was moving around the device while singing and you can hear nice effects with headphones.

Still have some placement issues, could have been closer to the drums and cello but I am pleased with the results.

Bdasilva, I think it is binaural, any feedback is appreciated.

http://www.padmasoundsystem.com/mp3-sound-healing-downloads/hrih may 24 2006.mp3
http://www.padmasoundsystem.com/mp3-sound-healing-downloads/medicine buddha may 24 2006.mp3

VA_TAPER · « **Reply #12 on:** May 29, 2006, 09:42:59 PM »

this thread so reminds me of a "Radio-Electronics" magazine article that made a stereo parabolic microphone system out of two radioshack parabolic cigarette lighters (yes there was such a beast), two panasonic capsules and a converted two-beer can holding hat....very cool if you could find someone to wear it.

damn I was a f'n nerdy kid...

peace, chris

cleantone · « **Reply #13 on:** May 30, 2006, 11:06:43 AM »

I just grabbed the "hrih may 24 2006.mp3" file. Seems to be some glitches and cuts. Overall is sounds pretty damn good! I haven't read the thread in full. This was with the parabolic you posted pics of? There is defnite seperation in the stereo field. I can't picture that rig having recorded this sample. Are the people singing behind the rig and the tabla's and strings in front of it? I'll have to read the thread. Cool shit at least.

EDIT:

just read more of the thread. Now I get why you devised this and how it was placed. I think this could work very well if you tweak the placement a little more. With these performers you obviously need to record live takes. I think stereo is definitly the route to take. Is this without an audience? I assume it is. I would also try a more typical stereo micing, maybe even omni's and a jecklin and have the singers closest to the mics and everyone else further away depending on volume needs and spaced from left to right to build the imaging you need. You might get better imaging with that technic. That would be a lot of fun!! This seems to work pretty well (with more placement tweaking) but the imaging is a bit less natural IMO. Good luck. Great project! I'm a little jealous.

yeshe · « **Reply #14 on:** May 30, 2006, 02:53:06 PM »

Thanks for your interest. Now is it binaural or not?

The objective is to record music that sounds best on headphones.

These are live recordings, the glitches are my limited equipment for post production.

I will be moving the mic closer to everything this Wednesday, learned alot about placement last time. I think this creates a rich sound and perfect for headphones.

but is it Binaural? I also tried to fix glitches:

http://www.padmasoundsystem.com/mp3-sound-healing-downloads/medicine buddha may 24 2006 remix.mp3

cleantone · « **Reply #15 on:** May 30, 2006, 02:59:39 PM »

I assume these are glitches that occured during the recording? I would definitly fix that ASAP. Your using a microtrack? Are you at 24bit 96khz? Does this mean that unit isn't even capable of sustained 24/96 recording? If this is the case I suggest dropping to 24/48 to avoid those dropouts.

yeshe · « **Reply #16 on:** May 30, 2006, 03:09:35 PM »

no I was recording at 16 bit 44hZ
since i was uploading mp3's at 44.1 I recorded at this setting and at 16 bit.
switching to 24 96 this Wednesday to see if it makes a difference.

The original recordings sound much better. i am using audacity to edit on a six year old Dell Latitude, very primitive post production right now. I think things will get better with Pro Tools and a G5, have to wait for that.

Nick's Picks · « **Reply #17 on:** May 30, 2006, 05:00:10 PM »

very interesting.
+

yeshe · « **Reply #18 on:** May 30, 2006, 10:50:19 PM »

No this is not Kirtan:

Nothing against Kirtan or new age music, well maybe something against new age music, but we wanted to create original improvised world music using Tibetan Buddhist mantra. Kirtan is a specific devotional form that has nothing to do with what we're creating, other than a sense of devotion to something numinous.

We're wanting to create an edgey kind of sound, with elements of contemporary brainwave frequency science, 2000+ years tradition of mind training, and recordings intended for headphone use.

These pieces are improvised acoustic Buddhist mind altering sound mandalas.

yeshe · « **Reply #19 on:** June 01, 2006, 06:21:26 PM »

http://www.padmasoundsystem.com/mp3-sound-healing-downloads/sky%20dragon%20may312006.mp3

New Mic placement of the parabolic turned out rather well I think...