Microphone

Enis Ulucay

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My AV System  
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Neumann KH310A
Hi

I am new with REW and just read that a USB-Mic is needed.

Is it possible to do the measurements with a real measurement microphone with XLR connections?

Many thanks in advance for the answers.
 

Wayne A. Pflughaupt

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Sure, no problem. All you need is a simple USB interface with mic pre-amp and phantom power. TASCAM and M-Audio make some, among others. The simpler, the better – feature-laden interfaces are typically problematic with REW. A calibration file for the mic is required for optimal results.

Regards,
Wayne A. Pflughaupt
 

Matthew J Poes

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Sure, no problem. All you need is a simple USB interface with mic pre-amp and phantom power. TASCAM and M-Audio make some, among others. The simpler, the better – feature-laden interfaces are typically problematic with REW. A calibration file for the mic is required for optimal results.

Regards,
Wayne A. Pflughaupt
Not to mention a lot harder to use. I just got a MOTU 828x and while I eventually figured it out, it was a serious pain. Even so, I basically know just enough about how it works to take proper measurements. Don’t ask me anything advanced about it.
 

Matthew J Poes

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Oct 18, 2017
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Hi

I am new with REW and just read that a USB-Mic is needed.

Is it possible to do the measurements with a real measurement microphone with XLR connections?

Many thanks in advance for the answers.
As already mentioned, complicated equipment is a bit hard to use. The main reason the USB microphone is suggested and popular is that it’s easy to use.

“Real” mics, even cheap phantom powered measurement mics tend to be a little quieter than the USB measurement mics. Not a huge issue but it’s a nice advantage.
 

akl

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MANY MANY MANY
The most precise measurements I do withOUT an USB-MIC. BUT it is complicated: a polarized MIC (200 V) capsule, a special PREpreAMP, a special Preamp (with calibrated meter) and the preamp of the AD-USB-Converter. Important for me is the level calibration. I use an USB-interface with stepped (repeatable !) gain. Also the preamp is switchable in 10 dB-steps. If just a level measurement is required I use the Preamp (and the mechanical Meter).

Of course USB-MICs must not be worse than standard MICs. BUT Precision USB-MICs use two AD converters with a gain-offset, switching intelligently from one to the other. It is difficult to cover the dynamic range of a good MIC capsule, even using 24 bit converters 2^24 == approx. 144 dB (ideal converter). Required is a dynamic range of > 150 dB ! usable > 25 bit !

The UMIK-1 has problems with the dynamic range, because of the (INTERNAL ! switchable) gain of 18 dB. The max. SPL level ist quite low. 18 dB gain is quite high . The noise of the mic is much higher than the 'bottom' of the AD-converter. May be the UMIKs converter is noisy losing some bit (effective 22 bit ?). I would be happy, if the standard gain of the UMIK-1 would bei DEcreased, probably the converter improved.

If the cal-file of the USB-MIC is properly done, a digital MIC like an USB-MIC has the big advantage, that you may measure ABSOLUTE level by software, right out of the box. You have got a good SPL-Meter. Other MICs require a special calibration procedure, that may be costly and/or inaccurate, allways time consuming. Often NOT repeatable (next measurement requires a calibration again). Also the frequency response of a digital MIC is 'fixed'. It may be somewhat corrected by correction tables. Some MIC amplifiers (USB-interface) show problematic (and also varying) frequency responses (at higher gains).
An ECM8000 is half the price of an UMIK-1, but my Phantom-MIC-USB-interfaces cost 15 to 50 x of an ECM8000. Precision needs money and brain. I have measured some really bad MIC-USB interfaces.

The only USB-MIC at (very) moderate cost, that is adaptable to a level calibrator is the UMIC-1 (please correct me), Though I judge the cal-level erroneous.

You may use a DAYTON UMM-6 if the cal-level is trustworthy. A Calibration may be cumbersome. (please correct me).

And I like the easy to handle USB-MIC , a small notebook/tablet and an USB-MIC. REW is easy to use. A trustworthy cal-file required.

One of my UMIK-1 ( just to verify) :

actual value 94.2 dB SPL (desired calibrator corrected 94.4), today 0.2 dB to low. -11.2 dB FS
( max SPL at 0 dB FS --> 105.4 or 105.6 dB SPL,
this is quite low, restricted application of UMIK-1)

my cal file ( corrected )
Sens Factor =4.6dB, SERNO: 703...

org cal file
Sens Factor =-0.015585dB, SERNO: 703...
gives wrong values
six decimal places are nonsense³ .

improved cal note
max spl = 105.6 dB SPL at 0 dB FS, SERNO: 703...
or
max spl =105.6dBSPL, SERNO: 703...
my proposal

does NOT work
*AKL CORRECTED 2018sep12 max105.4
Sens Factor =4.6dB, SERNO: 703...
comment capability of cal-file and software must be improved


This possibility to calibrate the absolute level is the main advantage of a digital output MIC : USB ,
also possible: SPDIF , aes3 , AES/EBU.


HIGH SPL oder low (noise) require complicated equipment, also 40 or 80 kHz measurements.
Also high precision. Sometimes many different software may be required ( REW , arta , HPWworks , HobbyBox , digicheck , ... ). My USB-interface allows easy to handle , easy to route digital outputs. The UMIK-1 driver behaves a littel 'bitchy'.

I use RME ( www.rme-audio.com ) UC UCX UFX .

An inexpensive NON-USB-MIC will definitely allow higher SPLs than common USB-MICs.


Have a nice noise- and distortionless 2019
(and a low SPL at home, night)

- akl -
 
Last edited:

Dave1952

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Dec 12, 2018
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AKI, how can I email your mic and test procedure? I don't see an email for you.
 

Enis Ulucay

New Member
Thread Starter
Joined
Dec 13, 2018
Messages
2
My AV System  
Front Speakers
Neumann KH310A
Sure, no problem. All you need is a simple USB interface with mic pre-amp and phantom power. TASCAM and M-Audio make some, among others. The simpler, the better – feature-laden interfaces are typically problematic with REW. A calibration file for the mic is required for optimal results.

Regards,
Wayne A. Pflughaupt

Thank you Wayne

I have the Fireface UCX Interface and a class 2 measurement microphone. Will do the measurements with them and the SPL meter might via App on the phone or I'll buy one.
 
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