Recommended microphone for initial Audiolense measurement

[Yulquen74]

Hi,

I have decided to give the Audiolense a go, but would like a recommendation for a good, affordable measurement microphone, preferably one with XLR connector.

Is it correct to assume it should have a pretty flat curve from 20Hz to 20KHz, and how much deviation can be tolerated? Crap in = crap out?
The Earhworks M23R deviates only +/-0.5dB, but it is at a premium price at $700.

Thanks in advance for any suggestions.

 

[juicehifi]

Yes, crap in equals crap out. It does not have to be a high end measurement mic, but it needs to be individually calibrated with decent quality.

Anything from Earthworks is very good. Microphones from Isemcon are also properly calibrated. And I believe LinearX microphones are good too. Those very affordable Behringer microphones are ok if they are properly calibrated as well. And I believe the Umic from MiniDSP passes the bar, although it has technical limitations that may or may not give you problems. If you have a sound card with ins and outs (and not just a da converter) I strongly recommend finding a microphone that you can plug into your sound card. It is by far the most technical robust solution that is most likely to work 100% without any significant trouble shooting.

Perhaps some of the members here will share their microphone experiences too.

 

[hulkss]

This mic works well: https://www.isemcon.net/shopus/prod..._id=9&MODsid=b86f0458e8918b74fc060c69216e7e99

 

[Yulquen74]

I have looked at the isemcon mic, and on the website is says "It can normally be used without the included freefield calibration data file for compensation. In this case take the individual calibration data as proof of its superb performance".

Sorry for the stupid question, but:
What does it mean that the mic is calibrated, and what is the data file for? Does the mic deliver +/- 0.5dB linearity out of the box, or do you need the data file and software processing later in the chain to flatten the frequency curve to this spesification, or to even further improve it?

 

[hulkss]

You need the calibration data file. All mics are that way unless the correction data is imbedded in the mic itself.

All measurement software, including AL, is made to work with the mic calibration files.

ISEMCON corrections are included for free field (outdoor use with no reflections, mic aimed at source) and diffuse field (Indoor use with room reflections, mic aimed at ceiling).

 

[juicehifi]

What he said.

 

[DanDan]

There is a 'hopefully' comprehensive list at the end of this beginners guide. There are more appearing all the time. e.g. Neumann MA1

 

[deercreekaudio]

Hi,

I have decided to give the Audiolense a go, but would like a recommendation for a good, affordable measurement microphone, preferably one with XLR connector.

Is it correct to assume it should have a pretty flat curve from 20Hz to 20KHz, and how much deviation can be tolerated? Crap in = crap out?
The Earhworks M23R deviates only +/-0.5dB, but it is at a premium price at $700.

Thanks in advance for any suggestions.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We recommend miniDSP UMIK-2:

• 32bit ADC with embedded PGA for up to 60dB analog gain
• 120dB SNR, Gain control via Mac/Win application
• Sensitivity: -34 dBfs at 0dB Gain (94 dB SPL. 1 kHz)
• Noise level: -105.3dBfs (A) at 0 dB gain
• MAX SPL(0dBfs): 125dB SPL
• Equivalent Input Noise (EIN): 20dB SPL at 0dB gain

Deer Creek Audio is an authorized miniDSP dealer.

 

[deercreekaudio]

We recommend miniDSP UMIK-2:

• 32bit ADC with embedded PGA for up to 60dB analog gainUMIK-2
• 120dB SNR, Gain control via Mac/Win application
• Sensitivity: -34 dBfs at 0dB Gain (94 dB SPL. 1 kHz)
• Noise level: -105.3dBfs (A) at 0 dB gain
• MAX SPL(0dBfs): 125dB SPL
• Equivalent Input Noise (EIN): 20dB SPL at 0dB gain

Deer Creek Audio is an authorized miniDSP dealer.

 

[juicehifi]

The umik is ok, but challenging. I spend most of my support time on assuring a reliable measurement. The rest is a piece of cake. Umik is perhaps involved in 80% of those problem cases. The other side of the equation is a multichannel usb dac. Two different usb devices seems to be the most fragile combo. One device (mic connected to the sound card has 10 times better odds). And Pci(e) card with Asio is extremely reliable.

The umic with calibration is ok, but the umik driver is substandard, and maybe the hardware too. The driver does not tell the user what the microphone can’t and shouldn’t do. And sometimes there seems to be some sort of resource conflict between a usb dac and a usb microphone.So usb dac plus umic users often have a very tough journey before they settle on an approach that produces reliable measurements.

Mitch Barnett is very good at sorting these issues out … for those who uses his services … and those of you who struggle. I do my best to help to resolve problems , but I do not take the same ownership in the outcome as Mitch does. Mitch completes my work.

 

[hulkss]

For me, it is important to have a calibration for 90 degree incidence (mic aimed at ceiling).

 

[DanDan]

LOL, as often happens I forgot to add the link.... https://www.avnirvana.com/threads/some-guides-to-rew-and-acoustic-measurement.121/page-2#post-49827

 

[jrobbins50]

I’ve used both UMIK-1 and -2 mics. I had a lot of problems with the -1. I usually have no issues using the -2 version with 90 degree calibration with my Okto dac8pro MCH DAC. However, I can’t plug both the mic and the DAC into the same USB over Ethernet extender to reach my Audiolense measurement PC in my back room. There is indeed some sort of USB conflict. I have to plug the DAC into the extender and separately run a powered USB extension cable directly into a USB input on the Audiolense measurement PC to avoid the conflict Bernt references, even though both are ultimately plugged into the same measurement PC. Go figure. Perhaps if I didn’t have the investment already in the UMIK-2, I’d pick a different mic. The results with Audiolense XO, though, are great (thanks again to Bernt). Cheers. JCR

 

[wus]

I'm using the iSEMcon EMX-7150 which is also used by professionals like this one. I chose it because every unit is supplied with individual calibration files for free field and diffuse field from 10Hz to 20kHz as a standard, from the manufacturer, because it can be used at SPLs up to 145dB, and it is moderately priced. I want to make distortion measurements on PA speakers, so I do need the high SPL capability.

What I didn't know when I bought a USB soundcard for it was that not all soundcards have "true" (hardware) input attenuators. So I bought the ESI Maya 22, which is basically good (low noise, low distortion), but its attenuator is software implemented. It turned out that its mic input starts to clip at SPLs around 115dB, regardless how much I pull down the input slider in its user interface.

So I'm now looking for a better soundcard that allows to take full advantage of the iSEMcon.

Have you guys out there any recommendation?

Unfortunately my budget is rather limited, if possible please consider this if you suggest one - thank you!

 

[hulkss]

Check this out: https://www.rationalacoustics.com/products/focusrite-scarlett-solo-gen-3

 

[deercreekaudio]

For me, it is important to have a calibration for 90 degree incidence (mic aimed at ceiling).

The miniDSP UMIK includes unique 90 degree and 0 degree calibration files that is downloaded from the miniDSP website using the serial number on your own UMIK.

 

[juicehifi]

I'm using the iSEMcon EMX-7150 which is also used by professionals like this one. I chose it because every unit is supplied with individual calibration files for free field and diffuse field from 10Hz to 20kHz as a standard, from the manufacturer, because it can be used at SPLs up to 145dB, and it is moderately priced. I want to make distortion measurements on PA speakers, so I do need the high SPL capability.

What I didn't know when I bought a USB soundcard for it was that not all soundcards have "true" (hardware) input attenuators. So I bought the ESI Maya 22, which is basically good (low noise, low distortion), but its attenuator is software implemented. It turned out that its mic input starts to clip at SPLs around 115dB, regardless how much I pull down the input slider in its user interface.

So I'm now looking for a better soundcard that allows to take full advantage of the iSEMcon.

Have you guys out there any recommendation?

Unfortunately my budget is rather limited, if possible please consider this if you suggest one - thank you!

That sounds reallly weird. You should be able to attenuate the incoming signal somewhere.

 

[DanDan]

Low cost http://www.uneeda-audio.com/pads/ I would probably make a 30dB, but do ask Isemcon about the powering issue.

 

[wus]

Check this out: https://www.rationalacoustics.com/products/focusrite-scarlett-solo-gen-3

Thank you. My microphone needs 48V phantom power. I could not find anything that confirms that the Solo's mic input supplies 48V phantom power. Neither in your link nor on the manufacturer's website. Can it really be?

 

[wus]

I did some more calculations with the Solo's and my mic's specs. My EMX-7150 has a sensitivity of 7.27mV/Pa @ 1kHz, which means @ 94dB SPL. From 94 to the mic's maximum SPL of 146dB is a difference of 52dB, or factor 398. So at 146dB SPL, the mic outputs 2.894V. The maximum "overshoot" according to my unit's individual calibration files is 2.5dB (@20kHz), or factor 1.333, resulting in a maximum output voltage of 3.858V.

The Solo's maximum max. mic input level at minimum gain (!) is 9dBu equalling 2,818V. That's not quite enough

 

[wus]

That sounds reallly weird. You should be able to attenuate the incoming signal somewhere.

I can attenuate the signal, but only after the mic preamp. When I learned about this detail, I looked up the Maya's input specs: its peak input level is only -15dBu, or 138mV.

Basically, even the Solo suggested by @hulkss has the same issue, just not quite as bad.

 

[wus]

Low cost http://www.uneeda-audio.com/pads/ I would probably make a 30dB, but do ask Isemcon about the powering issue.

I did already buy a commercially available attenuator that has switch selectable 10, 20 and 30 dB attenuation and came with 3 different calibration files for the 10, 20 and 30dB settings. According to the manufacturer it should work also with phantom powered mics. But my results were very odd, attenuation didn't reach anywhere near 30dB.

 

[firedog]

I've used the UMIK with a calibration file and an Earthworks for this application and couldn't tell any difference.

 

[juicehifi]

I've used the UMIK with a calibration file and an Earthworks for this application and couldn't tell any difference.

Yes, the Umik seems to do a good job when you find a way to do a reliable measurement.

 

[hulkss]

I did some more calculations with the Solo's and my mic's specs. My EMX-7150 has a sensitivity of 7.27mV/Pa @ 1kHz, which means @ 94dB SPL. From 94 to the mic's maximum SPL of 146dB is a difference of 52dB, or factor 398. So at 146dB SPL, the mic outputs 2.894V. The maximum "overshoot" according to my unit's individual calibration files is 2.5dB (@20kHz), or factor 1.333, resulting in a maximum output voltage of 3.858V.

The Solo's maximum max. mic input level at minimum gain (!) is 9dBu equalling 2,818V. That's not quite enough

If you measure up to 140 dB you can divide the voltage in half (from 146 dB). Are you sure you need over 140 dB?