Sign in with
Sign up | Sign in
Your question

Making binaural mics

Tags:
Last response: in Home Audio
Share
April 10, 2005 10:01:00 AM

Archived from groups: rec.audio.tech (More info?)

Hello,

I am interested in making a cheap set of binaural mics for home use.
I'm not very technically knowledgable though :-( I was wondering if
anyone could help me with my problem:

I bought 2 electret mic capsules from Maplin (a UK shop) and soldered
the ends of a set of headphones onto the contacts (I've only done one
capsule so far, because I don't want to go any further until I find out
what I'm doing wrong). The solder is still in 2 blobs - it hasn't run
where it shouldn't.

I plugged the jack (gold-plated) into my PC's line-in (the pink plug)
and tried to record using the basic Sound Recorder program on Windows
XP. It picks up very occasional "spikes", but no sound to speak of.
The spikes are so small that they don't even show up on the screen in
the program, though.

Does anyone know what I'm doing wrong here? Could you please help me?
Thanks a lot for any tips.

Liam

More about : making binaural mics

Anonymous
April 10, 2005 10:56:09 AM

Archived from groups: rec.audio.tech (More info?)

"Liam" wrote ...
> I am interested in making a cheap set of binaural mics
> for home use. I'm not very technically knowledgable
> though :-( I was wondering if anyone could help me
> with my problem:
>
> I bought 2 electret mic capsules from Maplin (a UK shop)
> and soldered the ends of a set of headphones onto the
> contacts (I've only done one capsule so far, because I
> don't want to go any further until I find out what I'm doing
> wrong). The solder is still in 2 blobs - it hasn't run
> where it shouldn't.

Are the headphone wires shielded? Do they have one insulated
wire in the middle and the other one wrapped (or braided)
around it (the shield)? Many headphone cables are NOT
shielded because headphone use doesn't require it. But
microphone signals DO require shielded wiring. If you don't
use shielded wiring, you will pick up all sorts of environmental
electromagnetic noise and interference. But since you can't
hear anything yet, you likely haven't discovered this issue.

> I plugged the jack (gold-plated) into my PC's line-in (the
> pink plug) and tried to record using the basic Sound Recorder
> program on Windows XP. It picks up very occasional "spikes",
> but no sound to speak of. The spikes are so small that they don't
> even show up on the screen in the program, though.

1) The "pink" connector should be the Mic input. The Line-In
is traditionally blue in my experience. If you truly plugged
your microphone into the LINE IN (of whatever color) it will
almost certainly not work. Those electret capsules require
power which the line input does not provide. Also mic level
is >1000 times lower than line level so the mic input has a
lot more gain.

2) Even if you had the mic plugged into the MIC input, the
way most computer mic jacks are wired won't work with
your intened wiring. First, most computer mic jacks are
monaural. Second, they use the tip connection for the mic
signal, and the "ring" connection for the mic power. Your
mic is wired more like the ones used for portable sound
recorders (MD, etc.) or video camcorders, etc.

If you want a better test of your creation, plug it into a more
suitable device. You didn't state what is your intended use
of your binaural microphone. If you want to use it with a
computer, you will likely need something with a STEREO
mic input. Some plug-in sound cards likely have stereo mic
inputs, but you should assume that they don't unless they say
otherwise.

> Does anyone know what I'm doing wrong here? Could you
> please help me? Thanks a lot for any tips.

You should also confirm that everything else is set up
properly (your sound card recording input selector and
input level controls, etc.) I would use a known good
conventional computer mic first just to confirm that all
the setup stuff is correct.

Good for you to experiment with your binaural mics.
Most of the people here would be happy to continue to
answer questions and help you with your project.
Anonymous
April 10, 2005 8:26:58 PM

Archived from groups: rec.audio.tech (More info?)

"Richard Crowley" <rcrowley7@xprt.net> wrote in message
news:115ic3t1turdd5c@corp.supernews.com...

> Are the headphone wires shielded? Do they have one insulated
> wire in the middle and the other one wrapped (or braided)
> around it (the shield)? Many headphone cables are NOT
> shielded because headphone use doesn't require it. But
> microphone signals DO require shielded wiring. If you don't
> use shielded wiring, you will pick up all sorts of environmental
> electromagnetic noise and interference. But since you can't
> hear anything yet, you likely haven't discovered this issue.

I've knocked up dummy head binaural stereo microphones using Yoga omni
lavalier mikes (from Maplins) and a cannibalised headphone lead, simply to
get the suppleness lacking from normal screened leads. (Suppleness is
important as the "dummy head" is my own!) I record to my MiniDisc mike
input, and have had no problem so far with hum pickup, and I'm certainly not
short of sensitivity. The headphone leads are so well twisted together that
there's very little space between signal and earth return (the insulator is
simply coloured varnish), and I guess this helps in keeping the hum to an
acceptable level. (However, I have heard hum when recording close to the
25kV electric overhead lines on the West Coast Mainline - but that was using
a single point stereo electret with a conventional looking screened(?)
microphone lead.)
My lead lengths are short, so I haven't needed to investigate balanced
leads.

--
M Stewart
Milton Keynes, UK
http://www.megalith.freeserve.co.uk/oddimage.htm
!