Calibrating an Open Theremin v3

Posted: 2/14/2018 8:39:57 PM
desmond

From: Montreal

Joined: 1/22/2018

Hi all,

I've recently begun to have some fun with the Open Theremin project.  I apologize if this has been discussed to death, but I'd like some advice, if possible. 

To those who have built their own Open Theremin v3, how do you calibrate it?  Specifically:

  • Where do you put your pitch hand while it's calibrating?
  • Where do you put your volume hand while it's calibrating?
  • How far away do you stand from the theremin while it's calibrating?
  • What does the end result of calibration look like?  I get that the zero beat is supposed to be roughly at your body (yes?  Or is it supposed to be behind it?), but what does the end result for volume calibration look like?

Thanks in advance!

Desmond

 

Posted: 2/14/2018 9:25:38 PM
Mr_Dham

From: Montpellier, Languedoc-Roussillon

Joined: 3/4/2012

Hello,

I am the guy who implemented MIDI interface on open Theremin V3.

Calibration of Open Theremin V3 should be done after a certain heating time. When components reach a stable state.

I personnaly calibrate it standing still at playing position with my arms along my body. I try to breath with a small amplitude in order to avoid disturbing the process.

When done well, if I put Pitch potentiometer at 12 o'clock, I have zero beat at my body in the 4 registers.

 

Vincent

Posted: 2/14/2018 9:33:39 PM
desmond

From: Montreal

Joined: 1/22/2018

"Hello, I am the guy who implemented MIDI interface on open Theremin V3. Calibration of Open Theremin V3 should be done after a certain heating time. When components reach a stable state. I personnaly calibrate it standing still at playing position with my arms along my body. I try to breath with a small amplitude in order to avoid disturbing the process. When done well, if I put Pitch potentiometer at 12 o'clock, I have zero beat at my body in the 4 registers.   Vincent"

Thanks for the response.

Stupid question: what exactly am I supposed to hear once the calibration is done?  Silence? Random noise?

Desmond

 

Posted: 2/15/2018 11:56:47 AM
Mr_Dham

From: Montpellier, Languedoc-Roussillon

Joined: 3/4/2012

Hello,

Normally, after calibration, if you perfectly stand still at playing position with your arms along your body and if volume and pitch pots are perfectly at 12 o'clock then you should hear a note (Middle C) during 1 second (indicating that calibration is finished) and then you should hear nothing until you move your hands. This is what we call being at zero beat position.

 

But, as this condition are not practically possible, you should hear a very low note or something like a motor running (because the note 's frequency is lower than human hear bandpass). The frequency will change slightly as you are breathing. You can tweak the pitch pot to try to have silence, a very low note or something else depending on your playing method. Of course if you put your hand close to volume antenna this sound will mute.

I won't go into long explaination here but there is one thing to have in mind:

On Open Theremin V3, zero beat position is a bit "virtual" compared to other models on which it result from a more physical principle. Due to that, quiet zone arround zero beat position is very narrow compared to quiet zone from other models.

Posted: 2/15/2018 11:26:57 PM
desmond

From: Montreal

Joined: 1/22/2018

Thanks again for the response. 

If I do as you describe, the "motor" sound at the start is audible, but I get a very "noisy" sound at the start of my pitch range, after which it sounds pretty good (note that my volume hand is on my lap)

This is what it sounds like:

https://soundcloud.com/desmond-rivet/open-theremin-range

Is this normal?  I'm assuming it's not normal.  Any insight is appreciated :)

Desmond

 

 

Posted: 2/16/2018 11:04:03 AM
Mr_Dham

From: Montpellier, Languedoc-Roussillon

Joined: 3/4/2012

Hello,

 

I am not listening in optimal audio condition (my laptop speaker) but it doesn't seem so much abnormal.

It looks like the motor sound that I am referring to. I am a bit surprised by the small gap that you seem to have between the motor sound and the note lowest "musical" note.

But maybe it is due to that my speaker cannot produce low frequency/note.

Do you have these low notes ?

Which register do you use ?

 

What I call a motor sound is a kind of "pop pop pop …" that comes from that Open Theremin V3 can produce infra-bass sound:

At infra-bass low frequency, up to 8hz, each period produces a "pop" in the speaker.

As the frequency raise you may not distinguish heach "pop"

At higher frequency you will start to hear a sound (bass, medium, then high)

 

One hint is that output signal of this device is quite loud, then the low frequency moto sound tend to be very loud.

Posted: 2/16/2018 12:30:37 PM
desmond

From: Montreal

Joined: 1/22/2018

Once again, thanks for the response.

"Hello,   I am not listening in optimal audio condition (my laptop speaker) but it doesn't seem so much abnormal. It looks like the motor sound that I am referring to. I am a bit surprised by the small gap that you seem to have between the motor sound and the note lowest "musical" note.

It's a pretty jarring shift, isn't it? I find it sounds pretty weird.

But maybe it is due to that my speaker cannot produce low frequency/note. Do you have these low notes ?

My speakers are pretty cheap, but I get the same results on better ones.

Which register do you use ?  

Everything is set to default. The register and timbre knobs are all the way to the left.  The volume and pitch knobs are at 12:00.

What I call a motor sound is a kind of "pop pop pop …" that comes from that Open Theremin V3 can produce infra-bass sound: At infra-bass low frequency, up to 8hz, each period produces a "pop" in the speaker. As the frequency raise you may not distinguish heach "pop" At higher frequency you will start to hear a sound (bass, medium, then high)   One hint is that output signal of this device is quite loud, then the low frequency moto sound tend to be very loud."

Is it not weird that there seems to be such sudden "cutoff" points?  They happen around 6s, 12s, 17s, 22s, 29s, 35s.

 

Posted: 2/16/2018 4:44:55 PM
Mr_Dham

From: Montpellier, Languedoc-Roussillon

Joined: 3/4/2012

I saw your other thread.

To conclude: I think that your OTV3 is correctly calibrated (So let's close this question) and that something is filtering low frequencies but it is another problem than calibration (So lets continue in the other thread...)

 

Posted: 2/16/2018 4:45:46 PM
Mr_Dham

From: Montpellier, Languedoc-Roussillon

Joined: 3/4/2012

Other thread : http://www.thereminworld.com/Forums/T/32058/open-theremin-v3-sounds-very-weird?post=213195#213195

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