• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

Adjusting the microphone to the interface

IncognitOz

Member
Joined
Oct 23, 2022
Messages
11
Likes
13
Hello, these days I am renewing my workstation. My purpose is mainly for measuring speakers, transducers and crossover design. The programs I intend to work with are ARTA & LIMP, and also REW. I'm getting into trouble with adjusting the interface to the microphone he has and I would appreciate it if someone could help me solve it please.

My problem is matching my microphone to the measurement system for acoustic measurement.
My connection look like this:
'Condenser Microphone' via 'External phantom power supply' to 'Cosmos ADC'.

I use "RME ADI2 dac fs" DAC converter that I am going to use as a frequency generator.

The ADC converter is the "E1DA Cosmos ADC" that I will use for sampling the measured device.

My microphone are "MicW M215L" with Sensitivity 40 mV/Pa, Impedance75 Ohms and Maximum SPL 145 dB SPL. The microphone is activated by supplying external phantom power 48V.

My question is, can I turn on the microphone and make measurements even at a high enough SPL (eg 130dB+) without a problem and not bring the Cosmos ADC input to clipping? (Max input in this ADC are 10V via XLR input)

Thank you very much.
 

wayne_handzus

Member
Joined
Oct 26, 2021
Messages
8
Likes
0
thats what the switchs are for on the bottom of the board.
to answer , yes
most assuredly yes.
wayne
 
OP
I

IncognitOz

Member
Joined
Oct 23, 2022
Messages
11
Likes
13
thats what the switchs are for on the bottom of the board.
to answer , yes
most assuredly yes.
wayne
Thanks for your answer.
I must update that I purchased only phantom power for the microphone and connected it to the Cosmos ADC. Unfortunately, I couldn't get enough gain even after playing with the DIP Switch. Finally I ordered the Cosmos APU which contains phantom power and also contains a preamplifier with a gain of 34&60 dB and now I get enough gain into my Cosmos ADC.
 

staticV3

Master Contributor
Joined
Aug 29, 2019
Messages
8,655
Likes
13,989
The Cosmos ADC's lowest input sensitivity using the XLR inputs is 10Vrms.
For your microphone to output 10Vrms, you'd have to record at 94+20*log10(10/0.04)=142dB SPL.
 

sarumbear

Master Contributor
Forum Donor
Joined
Aug 15, 2020
Messages
7,604
Likes
7,333
Location
UK
My question is, can I turn on the microphone and make measurements even at a high enough SPL (eg 130dB+) without a problem and not bring the Cosmos ADC input to clipping? (Max input in this ADC are 10V via XLR input)
1- make sure you wear ear protectors when testing levels over 130dBSPL. You can get deaf quickly otherwise.

2- Cosmos ADC is a line level device. It may work at above levels but not at normal levels. You need a preamp.

However, why not buy a USB measuring microphone and save money and reduce complexity?
 

sarumbear

Master Contributor
Forum Donor
Joined
Aug 15, 2020
Messages
7,604
Likes
7,333
Location
UK
The Cosmos ADC's lowest input sensitivity using the XLR inputs is 10Vrms.
For your microphone to output 10Vrms, you'd have to record at 94+20*log10(10/0.04)=142dB SPL.
It says 1.7V on their specs.

 
OP
I

IncognitOz

Member
Joined
Oct 23, 2022
Messages
11
Likes
13
1- make sure you wear ear protectors when testing levels over 130dBSPL. You can get deaf quickly otherwise.

2- Cosmos ADC is a line level device. It may work at above levels but not at normal levels. You need a preamp.

However, why not buy a USB measuring microphone and save money and reduce complexity?
Thanks. I agree for your 2 quotes. In any case, I did not purchase a USB microphone because of the inability to perform timing measurements with dual or semi-dual channel connection. In addition, I wanted a metal diaphragm Class1 microphone, probably a personal OCD nuisance ;)
 

sarumbear

Master Contributor
Forum Donor
Joined
Aug 15, 2020
Messages
7,604
Likes
7,333
Location
UK
Thanks. I agree for your 2 quotes. In any case, I did not purchase a USB microphone because of the inability to perform timing measurements with dual or semi-dual channel connection. In addition, I wanted a metal diaphragm Class1 microphone, probably a personal OCD nuisance ;)
There is nothing wrong with OCD but how do you know the frequency response of your particular Cosmos device in order to satisfy the Class 1 microphone quality?
 

wayne_handzus

Member
Joined
Oct 26, 2021
Messages
8
Likes
0
The Cosmos ADC's lowest input sensitivity using the XLR inputs is 10Vrms.
For your microphone to output 10Vrms, you'd have to record at 94+20*log10(10/0.04)=142dB SPL.
10volts?! Microphone?! 10V RMS is approximately 14.14427 volts peak. 28.2885 volts peak to peak. Advise recheck . I shall do so too. Done. yes the 10 volts is set using the do switchs, with no attenuation.
That is, With all dip switchs on 0 (or off) (or with an all spacing code combination.) (Binary zeros.) With that setting, 10 volts would be the absolute loudest signal, rite at the clipping point,10 volts= Full scale zero decibel full scale or 0 dBfs.
With a low gain Mic we use the 1.7 volt root means squared scale = 0 dBfs .
all switchs set on to the binary 1 position or all marking code combination.. at 1.7v rms we have a peak of near 2.4038 volts peak. Or 4.8 volts peak to peak. At that point we are at full scale decibel and we can record way down with cosmos a good hundred decibels below 0 should be excellent records. These are very accurate 32 bit pcm too. 4.29billion steps from neg 1.7 to positive 1.7 volts with noise in the middle area, so very accurate, allowing us further digital gain using 64 bit floating point math of cpu of computers. Very accurate. Computer gain is not the same as apu. Or tube pre. Push pull transistors and op amps etc increase signal level more then noise level. Where using digital gain 60db up in signal level brings the bottom end so called noise floor up 60db too.
so what was neg130 decibels is now up 60dB at neg 70dB noise floor. So using e1da apu preferred as it may only increase noise a few dB for 34dB gain. (Or some other type pre such as tubes, semiconductors, transistors, op amp etc pre). As you know, no doubt.
Later
Wayne
 
OP
I

IncognitOz

Member
Joined
Oct 23, 2022
Messages
11
Likes
13
There is nothing wrong with OCD but how do you know the frequency response of your particular Cosmos device in order to satisfy the Class 1 microphone quality?
I'm sorry, but I don't really understand your question. I have attached 2 pictures of my test equipment. One measurement shows the THD+N performance of the RME ADI2 DAC fs in a loop connection to the Cosmos ADC and the second picture shows the frequency response.
 

Attachments

  • IMG-20230331-WA0005(1).jpg
    IMG-20230331-WA0005(1).jpg
    162.9 KB · Views: 41
  • IMG-20230115-WA0007.jpg
    IMG-20230115-WA0007.jpg
    69.5 KB · Views: 178

sarumbear

Master Contributor
Forum Donor
Joined
Aug 15, 2020
Messages
7,604
Likes
7,333
Location
UK
I'm sorry, but I don't really understand your question. I have attached 2 pictures of my test equipment. One measurement shows the THD+N performance of the RME ADI2 DAC fs in a loop connection to the Cosmos ADC and the second picture shows the frequency response.
But your FR chart is empty!

index.php
 

sarumbear

Master Contributor
Forum Donor
Joined
Aug 15, 2020
Messages
7,604
Likes
7,333
Location
UK
Top Bottom