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Author Topic: miniDSP AmbiMIK-1 Ambisonic Mic  (Read 1741 times)

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Offline MIQ

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miniDSP AmbiMIK-1 Ambisonic Mic
« on: May 09, 2020, 04:45:34 PM »
I saw this new ambi mic from miniDSP this week.  Wondered if anyone else was checking it out?  Connects directly via USB cable.  https://www.minidsp.com/products/acoustic-measurement/ambimik-1  It looks neat.

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Offline IronFilm

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Re: miniDSP AmbiMIK-1 Ambisonic Mic
« Reply #1 on: June 23, 2020, 10:43:10 AM »
That was an emotional rollercoaster:

EXCITEMENT! "This is a very affordable ambisonics mic"

disappointment.... "oh dear, it is a USB mic"

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Re: miniDSP AmbiMIK-1 Ambisonic Mic
« Reply #2 on: June 23, 2020, 12:01:59 PM »
Wondering if it can be used directly into a phone..
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Re: miniDSP AmbiMIK-1 Ambisonic Mic
« Reply #3 on: June 23, 2020, 01:09:04 PM »
Wondering if it can be used directly into a phone..

From the specs:

USB Audio   
Linux/OSx/Android Driverless

ASIO compatible driver for Windows

iOS support with USB camera adaptor  (This is how the output of the new Sonosax M2D2 goes into an iPhone.  But what recorder app will do 4 channel 32 bit up to 192 kHz??)

However the VST plugin that controls it is only Windows/Mac.

??

Offline MIQ

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Re: miniDSP AmbiMIK-1 Ambisonic Mic
« Reply #4 on: June 24, 2020, 09:54:51 PM »

But what recorder app will do 4 channel 32 bit up to 192 kHz??)


Auria will do 24/96 multi-channel on the iPad but I don't know if it will recognize the AmbiMIK-1. 

I still don't see much multi-channel audio (beyond stereo) on the iPhone yet.  The Mofonix app I use for in ear monitor mixing will create multi-channel mixes on the iPhone but its tight if you are looking at more than one mix.  Looks better on an iPad.  Doesn't record yet.

https://mofonix.com/mofonix-app.html
« Last Edit: June 24, 2020, 10:00:16 PM by MIQ »

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Re: miniDSP AmbiMIK-1 Ambisonic Mic
« Reply #5 on: June 24, 2020, 11:07:07 PM »
its really difficult to do more than a few channels on ios lightning connector due to bus power limitations
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Offline MIQ

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Re: miniDSP AmbiMIK-1 Ambisonic Mic
« Reply #6 on: June 25, 2020, 12:13:05 AM »
its really difficult to do more than a few channels on ios lightning connector due to bus power limitations

I don't think Core Audio (the audio engine in Apple products) has any channel limitations for the lightning connector and the processors in most phones these days are plenty powerful to do many channels of audio.  If you get the $40 Apple camera connection kit with the charger port, buss power is not an issue at all.  I run 24 channels in, 24 out, with my Motu Ultralight Mk4 connected to an iPad or iPhone running the Mofonix App almost every day without any issues.  The buss powers the iPad, the Motu plugs into the wall.  You could power the iPad with a USB battery supply connected to the camera kit if you really wanted to, but you still need to plug the Motu into the wall or find another way to power it. 
« Last Edit: June 25, 2020, 12:21:00 AM by MIQ »

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Re: miniDSP AmbiMIK-1 Ambisonic Mic
« Reply #7 on: June 25, 2020, 12:18:22 AM »
that motu doesnt look bus-powered to me. theres a 15V DC jack on the back
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Re: miniDSP AmbiMIK-1 Ambisonic Mic
« Reply #8 on: June 25, 2020, 12:23:32 AM »
Yes I noted that, but that's how the device is powered.  I can't change that.  It's not the lightning connector that reduces the channel count is my point.  If you want to be battery powered with multi-channel audio on an iOS device you can do it.  It's not the lightning connector holding it back.

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Re: miniDSP AmbiMIK-1 Ambisonic Mic
« Reply #9 on: June 25, 2020, 12:35:23 AM »
Yes I noted that, but that's how the device is powered.  I can't change that.  It's not the lightning connector that reduces the channel count is my point.  If you want to be battery powered with multi-channel audio on an iOS device you can do it.  It's not the lightning connector holding it back.

again, bus power was the only limitation that i mentioned. im not aware of any 4 channel bus-powered devices

there are numerous devices like the motu that dont require bus power and work with OS
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Offline MIQ

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Re: miniDSP AmbiMIK-1 Ambisonic Mic
« Reply #10 on: June 25, 2020, 01:00:01 AM »
Sure, using the USB buss as a power source for the audio interface is not going to take you very far.  Are you expecting the iPhone or iPad to power your multi-channel interface? 

My point is that enabling multi-channel data on the lightning connector doesn't have anything to do with the buss power limitations.  As you noted, powering a multi-channel device with P48, a bunch of LEDs etc from USB power using the same lightning connector is not possible since it can't support that kind of power draw.

Motu Microbook II is 4 channel in "bus powered" but I think you still have to plug it into another USB port to give it enough power.  https://motu.com/products/motuaudio/microbook


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Re: miniDSP AmbiMIK-1 Ambisonic Mic
« Reply #11 on: June 25, 2020, 01:15:25 AM »
Sure, using the USB buss as a power source for the audio interface is not going to take you very far.  Are you expecting the iPhone or iPad to power your multi-channel interface? 

no, hence the post. I'm quite impressed that it can power 2 condenser mics a gain stage, and an ADC like with the d:vice, but thats nearing the limit of the power available
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Offline MIQ

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Re: miniDSP AmbiMIK-1 Ambisonic Mic
« Reply #12 on: June 25, 2020, 01:31:24 AM »
Yea d:vice is really neat.  I wish I could afford one.  ;D  This thread’s Ambi Mic with built in electrets and a2ds integrated inside the mic may have a chance of being buss powered like the d:vice. 

Offline Len Moskowitz (Core Sound)

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Re: miniDSP AmbiMIK-1 Ambisonic Mic
« Reply #13 on: July 13, 2020, 10:50:09 AM »
It's a first-order, generically calibrated microphone. For $349.

With a bit of luck, as a microphone it'll perform slightly better than the Zoom H3-VR recorder, but without the integral recorder. The Zoom retails for $249.
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Re: miniDSP AmbiMIK-1 Ambisonic Mic
« Reply #14 on: July 13, 2020, 01:52:22 PM »
Len,

When you write "generically calibrated mic", what does that mean?

Offline Len Moskowitz (Core Sound)

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Re: miniDSP AmbiMIK-1 Ambisonic Mic
« Reply #15 on: July 14, 2020, 11:15:40 AM »
"Generically calibrated" is the opposite of "individually calibrated."

Ambisonic microphones work on principles that depend on the very small differences between their capsules, plus a bunch of other factors. In this case and for the Zoom H3-VR, just because a microphone has four capsules mounted on a tetrahedral mount, that doesn't mean that it will work well.

It turns out that every microphone capsule is different. They might all meet the manufacturer's specifications, but those specifications have ranges of variation, and those variations are incredibly important for ambisonic microphones.

There are also other sources for variations in addition to the capsules.

Calibration is the process that measures the variations and provides corrections for them.

Because it takes time and equipment and manpower to test each of the capsules and then match them into sets, and because it costs money to test each assembled ambisonic microphone to develop correction files for each complete microphone, the manufacturers compromise. They make the assumption that all of their capsules are sufficiently matched, and all of their assembled microphones are sufficiently identical to use a single generic calibration correction.

From the beginning the assumptions are wrong. And as the microphones age, the assumptions get even worse. You're still stuck with the original generic calibration.

That's why each ambisonic microphone needs to be individually calibrated, and supplied with its own correction file. And as it ages, it will need to be re-calibrated.

Ideally, each set of capsules should be matched for a bunch of specifications - not just frequency response and/or sensitivity. And then when they're assembled into the microphone mount, each microphone should be measured so that its performance can be corrected with an individual calibration file.

All Core Sound OctoMics and TetraMics are individually calibrated. We recommend re-calibration every two to three years, depending on application. We offer a recalibration service for our microphones.

(We also offer an initial calibration service for other manufacturers' ambisonic microphones, including those from Rode, Sennheiser and the old Soundfield.)



« Last Edit: July 14, 2020, 12:46:03 PM by Len Moskowitz (Core Sound) »
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Re: miniDSP AmbiMIK-1 Ambisonic Mic
« Reply #16 on: July 14, 2020, 12:34:58 PM »
Hi Len,

I appreciate you taking the time to explain that.  When they state that they worked to create a "VST plugin specifically calibrated for the ambiMIK-1 with over 1200 measurements", they are talking about taking measurements of the mics in development and applying those measurements/calibrations to all the mics they produce, regardless of the slight differences in the individual capsules actually being assembled. 

I've read a fair bit about mic calibration, even the old Soundfield design (I'm a big fan of Gerzon), and can see how the costs could quickly get out of hand for a budget minded product.  As usual, the more accurate you get, the more time and money it takes. 

Offline Len Moskowitz (Core Sound)

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Re: miniDSP AmbiMIK-1 Ambisonic Mic
« Reply #17 on: July 14, 2020, 12:39:57 PM »
When they state that they worked to create a "VST plugin specifically calibrated for the ambiMIK-1 with over 1200 measurements", they are talking about taking measurements of the mics in development and applying those measurements/calibrations to all the mics they produce, regardless of the slight differences in the individual capsules actually being assembled. 

Yes. And the variations in mounting the capsules in the capsule mount. And the effects of the cables behind the capsules on the venting of the capsules. And others.

Some of the "slight differences in the individual capsules" are not slight. Some are quite large and significant.
« Last Edit: July 14, 2020, 12:45:18 PM by Len Moskowitz (Core Sound) »
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Re: miniDSP AmbiMIK-1 Ambisonic Mic
« Reply #18 on: July 14, 2020, 12:50:56 PM »
Len, how do you know for certain whether or to what extent other manufacturers calibrate the capsules for their ambisonic mics?  Or what those manufactures' internal specs are for the capsules they use in their ambisonic mics?
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Offline Len Moskowitz (Core Sound)

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Re: miniDSP AmbiMIK-1 Ambisonic Mic
« Reply #19 on: July 14, 2020, 01:05:18 PM »
Len, how do you know for certain whether or to what extent other manufacturers calibrate the capsules for their ambisonic mics?  Or what those manufactures' internal specs are for the capsules they use in their ambisonic mics?

We buy their mics and test them. As they do for ours.

We know that all the manufacturers match their capsules. Some do a better job than others. Some clearly don't test other important specifications. None of them calibrate completely assembled microphones, except perhaps one, and we think that they don't do a very good job. Almost all use a generic calibration.

In one case a generic calibration is warranted because they use MEMS elements as capsules; they are reliably long-term stable. They're noisy though.

The rest of the manufacturers use standard electret capsules. No matter how tightly matched they are during manufacture, two years (or less) downstream they've drifted.

One microphone manufacturer provides individual calibrations that correct for sensitivity variations only. They buy their capsules (they don't manufacture them) and presumably decided that correcting errors is less expensive than sorting for tightly matched capsules. They don't provide individual calibrations for the assembled microphones.

If you really want to know how good an ambisonic microphone is, look at its decoded polar directivity patterns - for example on a tetrahedral first-order microphone, look at the B-format's omni and the figure-8 channels . If they don't publish them, ask them why.

If they publish a frequency response specification, does it provide tolerances? If not, it's not real - it's a marketing specification. (Individual calibration allows for roughly two more octaves of bass.)

« Last Edit: July 14, 2020, 07:38:47 PM by Len Moskowitz (Core Sound) »
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