Room measurements

[vinylphilemag]

I've used REW + Tascam US-122 MK2 (and US-144 MK2) + calibrated Dayton EMM-6 (and Behringer ECM8000) with no issues.

I thought that would be the case, but appreciate the reassurance. Thanks!

 

[amirm]

Has anyone here actually tried the REW + Tascam US-122 Mk2 + calibrated Dayton EMM-6 combo and got it working? I'm about to pull the trigger on this stuff and although it looks like I should be good to go, a little reassurance in this area wouldn't go amiss...

Change out the EMM-6 for UMM-6 and you don't have to worry or buy the Tascam. Its noise floor is higher but doesn't matter for this type of analysis.

 

[Steve Williams]

I was just wondering what the Tascam does and where it fits or why it is even needed

 

[vinylphilemag]

Change out the EMM-6 for UMM-6 and you don't have to worry or buy the Tascam. Its noise floor is higher but doesn't matter for this type of analysis.

Thanks for the advice, but I already ordered the EMM-6... Audio nervousa kept me away from the higher noise floor mic, and I can put the Tascam's MIDI sockets to some use.

 

[vinylphilemag]

I was just wondering what the Tascam does and where it fits or why it is even needed

It does several things:

1. Supplies 48V phantom power to the mic.

2. Provides a way for the mic's signal to get into the measuring laptop while bypassing the usually iffy laptop mic input.

3. Provides a way for the computer generated tones to be connected to my amp.

As a bonus, it also has a couple of MIDI sockets, which are used to connect things like synthesisers and other keyboards to a sequencer.

Edit: This page has a good explanation, near the bottom is the set up I'm going to use. http://www.hometheatershack.com/for...ards/10001-rew-cabling-connection-basics.html

 

[Steve Williams]

It does several things:

1. Supplies 48V phantom power to the mic.

2. Provides a way for the mic's signal to get into the measuring laptop while bypassing the usually iffy laptop mic input.

3. Provides a way for the computer generated tones to be connected to my amp.

As a bonus, it also has a couple of MIDI sockets, which are used to connect things like synthesisers and other keyboards to a sequencer.

Edit: This page has a good explanation, near the bottom is the set up I'm going to use. http://www.hometheatershack.com/for...ards/10001-rew-cabling-connection-basics.html

and if you buy the mic Amir recommends, then you don't need it......what's there to think about

 

[vinylphilemag]

and if you buy the mic Amir recommends, then you don't need it......what's there to think about

Apart from having already ordered the EMM-6, I'd find the MIDI interfaces on the Tascam US-122 useful, if only every now and then.

Also, I'm not sure I could find a calibrated version of the mic that Amir recommended.

 

[microstrip]

Change out the EMM-6 for UMM-6 and you don't have to worry or buy the Tascam. Its noise floor is higher but doesn't matter for this type of analysis.

Amir,

Can the UMM-6 be used with a 5m USB cable? One of the nice things of my setup is that I have a 5m XLR cable and moving the microphone in the room does not oblige me to move the computer. Although getting rid of the EMU USB box would be very nice, I use it also as an audio spectrometer to check my equipment and tube quality.

A naive question - does the UMM-6 have an analogue volume or similar control? What is the 0dB level?

 

[amirm]

Amir,

Can the UMM-6 be used with a 5m USB cable? One of the nice things of my setup is that I have a 5m XLR cable and moving the microphone in the room does not oblige me to move the computer. Although getting rid of the EMU USB box would be very nice, I use it also as an audio spectrometer to check my equipment and tube quality.

5m is within USB cable max length so should work. I don't know how long the cable is that came with it but is pretty long.

A naive question - does the UMM-6 have an analogue volume or similar control? What is the 0dB level?

No analog level control. However, the latest REW version is supposed to be able to use the sensitivity setting in the calibration file that comes with it which eliminates the need to find the reference. I personally don't care about level calibration for room optimization so have not bothered to check this out.

 

[amirm]

and if you buy the mic Amir recommends, then you don't need it......what's there to think about

The one I recommended just came out in the last few weeks. Prior to that, the only solution was what was proposed with outboard USB adapter. It sure makes things simple to use and a lot less components to plug in, power up, etc.

 

[microstrip]

No analog level control. However, the latest REW version is supposed to be able to use the sensitivity setting in the calibration file that comes with it which eliminates the need to find the reference. I personally don't care about level calibration for room optimization so have not bothered to check this out.

Thanks - do you know what is the sampling rate and bit resolution of this mic? I am convinced - all I need now is to find some one supplying it in Europe!

 

[amirm]

Thanks - do you know what is the sampling rate and bit resolution of this mic? I am convinced - all I need now is to find some one supplying it in Europe!

As far as I know, it follows the sampling rate as set by the OS. Likely though it won't go above 48 Khz though.

BTW, here is a useful comparison chart of the *noise* floor of each mic:

The UMM-6 looks ugly there but note that its noise is at -70 dB. As long as you put 30+ dB into the room above that, you should be fine. Hopefully someone will make a cleaner version of this in the future.

 

[microstrip]

As far as I know, it follows the sampling rate as set by the OS. Likely though it won't go above 48 Khz though.

BTW, here is a useful comparison chart of the *noise* floor of each mic:

The UMM-6 looks ugly there but note that its noise is at -70 dB. As long as you put 30+ dB into the room above that, you should be fine. Hopefully someone will make a cleaner version of this in the future.

The 0dB is the digital clipping level? Do you know why there are such a high level of 1kHz harmonics in all the spectra? Can we assume it was a problem of the particular PC used for the measurements?

I am astonished that the EMM6a, inexpensive if we consider the typical prices of instrumentation microphones, can have a dynamic range of almost 130 dB between 1 and 10 kHz.

 

[vinylphilemag]

As far as I know, it follows the sampling rate as set by the OS. Likely though it won't go above 48 Khz though.

BTW, here is a useful comparison chart of the *noise* floor of each mic:

The UMM-6 looks ugly there but note that its noise is at -70 dB. As long as you put 30+ dB into the room above that, you should be fine. Hopefully someone will make a cleaner version of this in the future.

That noise floor graphic was one of the things that convinced me to go the EMM-6 route. I'm not made of money but the difference in price between the two approaches wasn't enough for me to forgo the EMM-6/Tascam US-122 route, especially as this is a one-off purchase.

 

[amirm]

The 0dB is the digital clipping level? Do you know why there are such a high level of 1kHz harmonics in all the spectra? Can we assume it was a problem of the particular PC used for the measurements?

It is not my test so I don't know if he calibrated to 0 dBFS. The graph is from the guy at Cross-Spectrum who calibrates these mics.

I am astonished that the EMM6a, inexpensive if we consider the typical prices of instrumentation microphones, can have a dynamic range of almost 130 dB between 1 and 10 kHz.

They are not saying that they have dynamic range of 130 db but rather, that is the maximum SPL they can handle. Here are the specs for UMM-6:

'Specifications: • Capsule type: Precision 6 mm electret condenser • Polar Response: True omnidirectional • Frequency response: 18-20,000 Hz (Calibrated) • Sensitivity at 1 kHz into 1K ohm: 10 mV/Pa (-40dBV, re. 0dB = 1V/Pa) • Maximum SPL for 1% THD @ 1000 Hz: 127 dB • S/N ratio: 70 dB (A-weighted) • Connector: USB B female • Weight: 148 grams."

 

[amirm]

That noise floor graphic was one of the things that convinced me to go the EMM-6 route. I'm not made of money but the difference in price between the two approaches wasn't enough for me to forgo the EMM-6/Tascam US-122 route, especially as this is a one-off purchase.

I hear you . But having gone from a mic with pre-amp to this plug and play USB mic, I have to say, the latter is just a joy to use. I measure so much more now that I don't have to string things together. I don't use my discreet setup anymore.

BTW, I forget who asked about the 1K harmonics . They are created I believe due to framing pulses over USB. In other words, the digital circuits are bleeding into the analog since they are so close to each other and don't have good filtering.

 

[andromedaaudio]

Although the ATB 801 now works properly it took sometime before i had everything up and running on the computer .
Nice ones ( i ve read ) that are on the market are for example the clio 10FW http://www.audiomatica.com/wp/
Or the : forever to get ready and still not in production linearx 500 http://www.linearx.com/products/analyzers/LX500/LX500_01.htm

I never understood why kirchner stopped the production of the ATB precision

 

[DonH50]

I'm on Amir's page with a USB mic for measurements. You don't need great dynamic range for that, and calibrated versions are still a fraction the cost of my earthworks measurement mic. I have not got one but it is on my list. My earthworks is an incredible mic, but I have to use an outboard preamp, and my old notebook has to use an outboard sound card, so it's a lot of stuff to haul into the media room. Then, that old notebook won't power the USB preamp I have, so I have to drag down a power supply for it, and USB hub.

Yeah, I need a new notebook too...

 

[microstrip]

Most people are referring we do need a large dynamic range for for audio measurements - however in order to properly measure RT60 we need a low noise floor. Although most of the time software interpolate RT60 from RT30, as we do not have absolute noise levels in the shown measurements, how can we be sure that these horrible spikes from the UMM-6 do not affect the decay measurements?
Yes, Amir I know you are not an RT60 dependent ...

 

[andromedaaudio]

This is the freq response of the mike i use ,http://www.nady.com/manuals/microphones/cm100.pdf
And having a precise /neutral signalgenerator off course