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Digitaly Matching Microphones w/ Voxengo CurveEQ

Posted: Mon Dec 18, 2017 12:50 pm
by 12strings2hands
The Voxengo CurveEQ can generate an EQ curves based on the input, in this case they use pink noise through 2 microphones and you can use the curves to make one mic match the other.
Given that there are a lot of other differences between mics, I can see a lot of uses for something like this.
Is there a linux equivalent?
Here's a couple of links to the subject:
https://groupdiy.com/index.php?topic=67322.msg0
https://www.youtube.com/watch?v=0qoGEpOuY6U

Re: Digitaly Matching Microphones w/ Voxengo CurveEQ

Posted: Tue Dec 19, 2017 2:13 pm
by CrocoDuck
Hi there!

I am not sure whether there is a Linux equivalent, but you can do it on Linux I think.

Here I wrote a tutorial to do Audio response measurements using JAPA (still work in progress). There is a section on how to measure the relative response of two microphones.

With reference to that, what I think you could do is to put an EQ (Calf EQ for example) right between mic 1 output and JAPA in_1. Then, you could tweak the EQ until you obtain a flat horizontal line on JAPA. This would give you the EQ that matches mic 1 response to mic 2 response.

If the EQ you use adds too much latency (see soundcard measurement to see the effects of latency), just put the same EQ between mic 2 and JAPA in_2, but set that to flat.

Although I know that the reference method works (as I use it everyday for my job) I never tried it with JAPA. I plan to do some more experiments during the xmas break, when I will be back to home to play with my mics :wink:

Re: Digitaly Matching Microphones w/ Voxengo CurveEQ

Posted: Tue Dec 19, 2017 2:35 pm
by sadko4u
I think we can add something similar to the long-long TODO list of LSP Plugins.

Re: Digitaly Matching Microphones w/ Voxengo CurveEQ

Posted: Thu Dec 21, 2017 12:36 am
by 12strings2hands
CrocoDuck wrote:Hi there!

I am not sure whether there is a Linux equivalent, but you can do it on Linux I think.

Here I wrote a tutorial to do Audio response measurements using JAPA (still work in progress). There is a section on how to measure the relative response of two microphones.

With reference to that, what I think you could do is to put an EQ (Calf EQ for example) right between mic 1 output and JAPA in_1. Then, you could tweak the EQ until you obtain a flat horizontal line on JAPA. This would give you the EQ that matches mic 1 response to mic 2 response.

If the EQ you use adds too much latency (see soundcard measurement to see the effects of latency), just put the same EQ between mic 2 and JAPA in_2, but set that to flat.

Although I know that the reference method works (as I use it everyday for my job) I never tried it with JAPA. I plan to do some more experiments during the xmas break, when I will be back to home to play with my mics :wink:


That's brilliant! I'm going thru the tutorial - it will take a while :-)
I don't know if Calf EQ will be precise enough to flatten the A/B graph, but I'll also be spending some xmas time on this. :D
Thanks.

Re: Digitaly Matching Microphones w/ Voxengo CurveEQ

Posted: Sat Dec 23, 2017 8:37 pm
by 12strings2hands
CrocoDuck wrote:Hi there!

I am not sure whether there is a Linux equivalent, but you can do it on Linux I think.

Here I wrote a tutorial to do Audio response measurements using JAPA (still work in progress). There is a section on how to measure the relative response of two microphones.

With reference to that, what I think you could do is to put an EQ (Calf EQ for example) right between mic 1 output and JAPA in_1. Then, you could tweak the EQ until you obtain a flat horizontal line on JAPA. This would give you the EQ that matches mic 1 response to mic 2 response.

If the EQ you use adds too much latency (see soundcard measurement to see the effects of latency), just put the same EQ between mic 2 and JAPA in_2, but set that to flat.

Although I know that the reference method works (as I use it everyday for my job) I never tried it with JAPA. I plan to do some more experiments during the xmas break, when I will be back to home to play with my mics :wink:


I tried JAPA as you suggested. I started an Ardour session and told it to use Jack. I added a couple of Audio Tracks in Ardour and told them to use my hardware microphone inputs. I started "japa -J" in another window (it was a nice surprise to see the japa inputs automatically show up as output options in in each the Ardour Audio Tracks).

I fed some pink sound into pairs of mics and fiddled around with the JAPA buttons and Ardour faders to match the input levels. It was interesting to see the frequency response as well as the difference (by selecting "A/B" from the A input options) between the 2 mics.

I think I avoided the latency issue you described in your tutorial https://linuxmusicians.com/viewtopic.php?f=19&t=17759 by inserting Calf 12 band eq's in each track, but only using one on the mic that I wanted to match to the reference. I checked this by setting both inputs to the same mic. JAPA indeed showed a straight line.
Image

Re: Digitaly Matching Microphones w/ Voxengo CurveEQ

Posted: Mon Dec 25, 2017 7:25 pm
by CrocoDuck
12strings2hands wrote:I think I avoided the latency issue you described in your tutorial viewtopic.php?f=19&t=17759 by inserting Calf 12 band eq's in each track, but only using one on the mic that I wanted to match to the reference. I checked this by setting both inputs to the same mic. JAPA indeed showed a straight line.
Image


Nice one! Did you attach a picture? I think I cannot see it.

Anyway, I was not able to do more experiments on my side. Guess what: my Scarlett 2i4 broke as I pressed the +48V button to power up a couple of mics. It is the second time this happens to me, but the first time it happened while the unit was still under warranty... I guess I am not gonna buy another Focusrite card. So bad, cause they work just great under Linux.

Re: Digitaly Matching Microphones w/ Voxengo CurveEQ

Posted: Sat Dec 30, 2017 12:09 am
by 12strings2hands
I made a little entry on my music blog to host the image of the JAPA session. There's an explanation also:

http://www.artsulger.com/2017/12/digital-mic-matching-using-japa.html