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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => Audio Measurement and Testing => Topic started by: Doug Fowler on April 01, 2015, 01:15:38 pm

Title: Measurement Interfaces
Post by: Doug Fowler on April 01, 2015, 01:15:38 pm
Discuss :-)
Title: Re: Measurement Interfaces
Post by: Ivan Beaver on April 01, 2015, 07:08:55 pm
I know I will get some flack for this, but here is a interface that simply works.

No software-no drivers.

Just plug it in and the software will see it.  Select "device" and you are good to go.

The price is right-so if you lose it-no big deal.

The cheaper one is the Behringer UMC202.  If you want balanced outputs and more inputs the UMC404.

I have been playing around with it for a little while and am pleased.

Every now and then there is a "diamond in the rough".
Title: Re: Measurement Interfaces
Post by: Jay Barracato on April 01, 2015, 07:16:40 pm
Smaart IO

FOH space is often limited on walkups so I like the low profile and not needing external power.

Sent from my DROID RAZR HD using Tapatalk

Title: Re: Measurement Interfaces
Post by: David Sturzenbecher on April 01, 2015, 08:39:28 pm
USBpre2 for quick small footprint jobs, Octacapture for multi-mic measurements. Love the digital gain adjustment. 


Sent from my iPhone using Tapatalk
Title: Re: Measurement Interfaces
Post by: John L Nobile on April 01, 2015, 11:46:22 pm
I know I will get some flack for this, but here is a interface that simply works.

No software-no drivers.

Just plug it in and the software will see it.  Select "device" and you are good to go.

The price is right-so if you lose it-no big deal.

The cheaper one is the Behringer UMC202.  If you want balanced outputs and more inputs the UMC404.

I have been playing around with it for a little while and am pleased.

Every now and then there is a "diamond in the rough".

No flack from me. Behringers always had one or 2 diamonds in the rough. I've always been impressed by what the product does for the price. As long as you don't try to compare them to hi end gear they work okay and I feel that gap is closer lately
Title: Re: Measurement Interfaces
Post by: Peter Kowalczyk on April 02, 2015, 03:07:27 pm
I've been using the MOTU 828 (mkII) that I bought used years ago as a smaart interface.  It recently suffered its second firewire port failure, and given that I no longer need its I/O count (Using Smaart 7DI; other multi-channel I/O needs covered by an X32Rack), I'm hesitant to take on another board-level repair job on the MOTU.

I have been lusting after a Sound Devices USBpre2 for some time.  However, I'm not sure if I can justify the cost when there are numerous other 2x2 balanced i/o devices at a fraction of the price, e.g. the presonus audiobox usb, or the berry-box that Ivan mentioned.

David - what about the USBpre2 made you choose it over more economical options?  Is the USBpre2 that much better?

Cheers,
P
Title: Re: Measurement Interfaces
Post by: Lyle Williams on April 02, 2015, 05:34:59 pm
As cheap and compact a transfer function rig as I could find!

Calibrated Mic: Dayton EMM-6
Interface: ART USB Dual Pre
Platform: iPad Mini
Software: Studio Six Digital's AudioTools

Title: Re: Measurement Interfaces
Post by: David Sturzenbecher on April 02, 2015, 09:55:19 pm


David - what about the USBpre2 made you choose it over more economical options?  Is the USBpre2 that much better?

Cheers,
P

I chose the usbPre2 because at the time, is was really the standard in a "measurement pre".   Also, it's wasn't my dime.   I used an EASERA gateway, before and absolutely hated it. It was very unreliable. The USBpre2 just works.  It has built in loopback which is very handy, and  selectable input routing which is pretty slick too. Oh XLR outputs... Why can't all preamps have that?


Sent from my iPhone using Tapatalk
Title: Re: Measurement Interfaces
Post by: Chris Tsanjoures on April 06, 2015, 03:54:10 pm
The Smaart IO is my main workhorse. I love that with Smaart Di it will configure itself as default - just connect it to your computer, launch DI, and you are ready to make measurements without selecting or creating a config.

That and its ability to calibrate the inputs for SPL without needing a piston calibrator (just the mic's sensitivity value), makes it a no-brainer. There are plenty of other 2 channel interfaces that have more robust features for the home-recording guy, but there aren't any others that have this gain reporting feature so the SIO works best for me, for what I do.
Title: Re: Measurement Interfaces
Post by: Miguel Angel Castro Rios on October 04, 2016, 01:54:04 pm
As cheap and compact a transfer function rig as I could find!

Calibrated Mic: Dayton EMM-6
Interface: ART USB Dual Pre
Platform: iPad Mini
Software: Studio Six Digital's AudioTools

I know you posted this long time ago, What's your opinion on the Dayton emm-6, I read somewhere that the calibration is not very good and the Mic capsule is a Panasonic?
Is this true? I have very limited budget and only need it to align subs with pa and front fills.
Title: Re: Measurement Interfaces
Post by: Scott Carneval on October 04, 2016, 02:00:54 pm
I've been using the SMAART I/O for several years, but I've recently started using my Behringer XR18 for multi-channel measurements. I was looking for a new interface when it dawned on me that the Behringer essentially IS an 18ch USB interface. It actually saves a piece of gear because it's my mixer and interface all in one.
Title: Re: Measurement Interfaces
Post by: Mark McFarlane on March 02, 2017, 11:46:43 pm
I know I will get some flack for this, but here is a interface that simply works.

No software-no drivers.

Just plug it in and the software will see it.  Select "device" and you are good to go.

The price is right-so if you lose it-no big deal.

The cheaper one is the Behringer UMC202.  If you want balanced outputs and more inputs the UMC404.

I have been playing around with it for a little while and am pleased.

Every now and then there is a "diamond in the rough".


Ivan, regarding SMAART interfaces, the UMC404 has been replaced by a newer version UMC404HD. Pretty cheap at $99 for 4 mic preamps and the XLR outs are a bonus.  It has global phantom.


Have you ever had a problem with global phantom and looping back your reference from/to your UMC202?  I had a problem years ago with an Edirol interface where the phantom power messed up the loopback signal.


Lately I've been using my GLD as a SMAART interface, but I'm starting to work on other people's systems more frequently and need at least 4 portable channels. $99 is pretty much a no-brainer investment.
Title: Re: Measurement Interfaces
Post by: Nathan Riddle on March 03, 2017, 10:47:47 am

Ivan, regarding SMAART interfaces, the UMC404 has been replaced by a newer version UMC404HD. Pretty cheap at $99 for 4 mic preamps and the XLR outs are a bonus.  It has global phantom.


Have you ever had a problem with global phantom and looping back your reference from/to your UMC202?  I had a problem years ago with an Edirol interface where the phantom power messed up the loopback signal.


Lately I've been using my GLD as a SMAART interface, but I'm starting to work on other people's systems more frequently and need at least 4 portable channels. $99 is pretty much a no-brainer investment.

I thought it was just a bad idea period to run phantom into an output. I use the an XLR-F to TRS-M for the reference signal.
Title: Re: Measurement Interfaces
Post by: Mark McFarlane on March 04, 2017, 02:33:00 pm
I thought it was just a bad idea period to run phantom into an output. I use the an XLR-F to TRS-M for the reference signal.


You are correct. I think I didn't have the right cable,... it was a decade ago.
Title: Re: Measurement Interfaces
Post by: Keith Broughton on March 04, 2017, 03:05:37 pm

Ivan, regarding SMAART interfaces, the UMC404 has been replaced by a newer version UMC404HD. Pretty cheap at $99 for 4 mic preamps and the XLR outs are a bonus.  It has global phantom.


Have you ever had a problem with global phantom and looping back your reference from/to your UMC202?  I had a problem years ago with an Edirol interface where the phantom power messed up the loopback signal.


Lately I've been using my GLD as a SMAART interface, but I'm starting to work on other people's systems more frequently and need at least 4 portable channels. $99 is pretty much a no-brainer investment.
I use the 404HD and take a TRS from out 4 (set as test out) and loop it back (TRS) to input 4.
This gives 1-3 mic channels with phantom for measurements and channel 4 is reference.
No issue with phantom on TRS inputs.
Title: Re: Measurement Interfaces
Post by: Ivan Beaver on March 04, 2017, 03:55:26 pm

Ivan, regarding SMAART interfaces, the UMC404 has been replaced by a newer version UMC404HD. Pretty cheap at $99 for 4 mic preamps and the XLR outs are a bonus.  It has global phantom.


Have you ever had a problem with global phantom and looping back your reference from/to your UMC202?  I had a problem years ago with an Edirol interface where the phantom power messed up the loopback signal.


Lately I've been using my GLD as a SMAART interface, but I'm starting to work on other people's systems more frequently and need at least 4 portable channels. $99 is pretty much a no-brainer investment.
My standard cable that I use for dual transfer functions has a TRS on one end-but only hooked up to the T and S.

There are 2 cables that come out of the connector.
The connector plugs into the headphone output.

One is a TRS-with the hot to tip and the shield to R (no connection to shield)
This goes to the TRS input of the reference channel

The other cable is a MXLR that has the tip hooked to pin2 and the shield hooked to pin 3.

This allows me to vary the SPL out of the loudspeaker, without affecting the signal displayed-since both the reference and measurement go up and down at the same time.

It is also REAL good for looking at power compression of drivers in real time.
Title: Re: Measurement Interfaces
Post by: Langston Holland on August 18, 2018, 09:44:12 pm
Hello fellow cheapskates*:

I thought this would be of interest. :)

Advertisements for the Focusrite Scarlett 2i2 Gen 2 claim it to be the best selling audio interface of its type in the world. Given its low price, good looks, massive advertising budget and great specs (except the ones they don't mention), I can see why.

Summary

Buy this thing if you use Smaart or SysTune.

It is a great USB bus powered choice for dual channel FFT measurement at 96k sample rates and below. It's output noise at higher sample rates is so bad that they shouldn't have enabled it. Input is very quiet but I still would never consider this unit for what it's advertised for (recording) because of its poor phase performance. The time domain error is the same on each channel, thus cancels out with the magic of dual channel FFT. With recording it does not cancel - it's permanently embedded in your tracks.

If Focusrite fixed the phase error on the input channels this thing would be the steal of the century for home studio tracking and even more serious stuff. My speculation is that they compromised phase in order to reduce latency as is done with digital wireless. Low latency is a big deal for monitoring during recording.

Odds and Ends

Measurement gizmos used were the Audio Precision APx515, FIR Capture, Keysight U1282A and U1733C. The Focusrite Windows ASIO driver is solid as a rock. The APx515 allows you to send or receive from a DUT through ASIO, thus allowing closed loop measurement of the analog inputs and outputs independently.

Phantom power is excellent, 47.6V unloaded and 14.3V when both channels have full 10mA loads. The outputs are unaffected by the presence of phantom power. XL input impedance is 3,025Ω from 100Hz to 10kHz, sloping down to 2,115Ω at 100kHz. This impedance is the same with or without phantom power engaged. Construction is above average disposal class; you probably have to pry off the back panel to get at the screws. Input signal and clip indicators are nicely visible, cool looking and accurate.

Measurements

This unit has analog gain adjustments for both input and output, thus you should adjust both so that you can keep the digital signal as close to full scale as possible. I chose -3dBFS for these measurements. The mfg specs use -1dBFS, which isn't safely achievable in use.

Flat lines from a dual channel FFT measurement program called FIR Capture at each of the tested sample rates:

(http://soundscapesweb.com/files/PSW/2i2review/Dual_FFT_Loopback.png)

Phase input and output:

(http://soundscapesweb.com/files/PSW/2i2review/Phase_Input.png)

(http://soundscapesweb.com/files/PSW/2i2review/Phase_Output.png)

Magnitude input and output:

(http://soundscapesweb.com/files/PSW/2i2review/Magnitude_Input.png)

(http://soundscapesweb.com/files/PSW/2i2review/Magnitude_Output.png)

Noise input and output:

(http://soundscapesweb.com/files/PSW/2i2review/FFT_Noise_Input.png)

(http://soundscapesweb.com/files/PSW/2i2review/FFT_Noise_Output.png)

Distortion at -3dBFS:

(http://soundscapesweb.com/files/PSW/2i2review/THD_Input.png)

(http://soundscapesweb.com/files/PSW/2i2review/THD_Output.png)

(http://soundscapesweb.com/files/PSW/2i2review/IMD_SMPTE_Input.png)

(http://soundscapesweb.com/files/PSW/2i2review/IMD_SMPTE_Output.png)

(http://soundscapesweb.com/files/PSW/2i2review/IMD_DFD_Input.png)

(http://soundscapesweb.com/files/PSW/2i2review/IMD_DFD_Output.png)

And my Pin 1 torture test. Very few gizmos have passed it:

(http://soundscapesweb.com/files/PSW/2i2review/Pin_1_FFT_Noise.png)

(http://soundscapesweb.com/files/PSW/2i2review/Pin_1_RMS_Noise.png)

*A cheapskate is a semisentient being that spends twice as much money at four times the grief as the buy-once, cry-once heretic.
Title: Re: Measurement Interfaces
Post by: David Sturzenbecher on August 18, 2018, 10:55:41 pm
Hello fellow cheapskates*:

I thought this would be of interest. :)

*A cheapskate is a semisentient being that spends twice as much money at four times the grief as the buy-once, cry-once heretic

Thank you for the analysis Langston!  My Scarlett 2i2 went belly up just a week or so ago. Initial observations see a bulging-open bottom electrolytic cap on the PCB. The device was great to throw in the backpack when octacapture was overkill. Still debating if it's worth tracking down the specific capacitor, and troubleshoot if there are other issues.



Sent from my iPad using Tapatalk Pro
Title: Re: Measurement Interfaces
Post by: Langston Holland on August 18, 2018, 11:46:41 pm
Quote
Initial observations see a bulging-open bottom electrolytic cap on the PCB...

Hi David:

How did you take it apart? Is it just an issue of prying off the rear panel?

Don't bother if it isn't easy, but a picture of the internals would be fun. :)

Edit: Skip it - sorry I didn't think about YouTube. (2) Screws under the rear rubber feet and you're in like Flynn. :)
Title: Re: Measurement Interfaces
Post by: Nathan Riddle on August 19, 2018, 02:44:48 pm
Hello fellow cheapskates*:

Advertisements for the Focusrite Scarlett 2i2 Gen 2 claim it to be the best selling audio interface of its type in the world. Given its low price, good looks, massive advertising budget and great specs (except the ones they don't mention), I can see why.

Langston,

I have a first gen 2i2 sitting on my desk that I've been using to take measurements, I wonder how they compare?

I am a short drive away, maybe we can meet up sometime?
I love this geek-out/test-n-review stuff you do!
Title: Re: Measurement Interfaces
Post by: Mark Wilkinson on August 19, 2018, 07:32:34 pm
Hello fellow cheapskates*:

I thought this would be of interest. :)

Advertisements for the Focusrite Scarlett 2i2 Gen 2 claim it to be the best selling audio interface of its type in the world. Given its low price, good looks, massive advertising budget and great specs (except the ones they don't mention), I can see why.



Thx Langston, and in keeping with cheapskate....have you measured the UMC404HD ?   Same price...
I know it at least has much better phase performance ...not to mention 4 ch....
Title: Re: Measurement Interfaces
Post by: Langston Holland on August 21, 2018, 02:45:14 am
Hi Mark:

I'd be glad to measure anything that would have a general interest to folks on PSW, and I think that unit fits on the low end. Anyone that really want this - just PM me and I'll figure out my schedule and you can ship it to me. I'll do it within two business days and ship it back.

There are lots of variables with audio interfaces for measurement that aren't obvious that the Scarlett 2i2 did well with. One is USB jitter and many units, including more expensive ones like the Tascam UH-7000, fail in this area and are unusable with the MLS stimulus that many still use for acoustics.
Title: Re: Measurement Interfaces
Post by: Langston Holland on August 21, 2018, 01:39:56 pm
Quote
I have a first gen 2i2 sitting on my desk that I've been using to take measurements, I wonder how they compare?

Hi Nathan:

I just did a little search and found a couple of interesting things about the Gen 1 unit:

1. It was spec'd to 96k max. Thus the (unusable IMO) 192k of Gen 2 is likely driver implemented without hardware upgrades.

2. Gen 1 now uses the Gen 2 driver (4.x series) with the same latency reduction. Maybe the Gen 1 driver (3.x series), which I can't find on the Net, would fix or reduce the phase error in the Gen 2 unit in exchange for increased latency.

It'll be fun if the mfg. fusses at me about these posts, but they won't. It'd put attention on things that would be better ignored from their POV.
Title: Re: Measurement Interfaces
Post by: Langston Holland on August 23, 2018, 08:25:41 pm
Meanwhile, on the other side of the railroad tracks...

Hello fellow buy-once, cry-once heretics!

In case you were looking for an end-game for a two channel audio interface for measurement (and recording), the RME Babyface Pro is a bargain IMO.

Build quality is Apple computer, Lectrosonics, Mercedes, etc. It's just wonderful. The Windows WDM and ASIO drivers are the best and most flexible I've ever seen. The included routing software includes basic, but excellent EQ and effects. This ain't Behringer - everything that comes with this device is something someone is proud of, not something birthed in marketing.

Summary

Sample rates from 32k to 192k show near theoretical noise floors on both input and output. Because USB is an asynchronous animal, SR's can be adjusted in 0.001% increments around the primary frequency for syncing with other stuff that's not playing by the rules (common).

Its channels have identical transfer functions, so dual channel FFT is dead accurate at any SR. Its USB bus powered or externally powered in stand-alone mode (mic preamp, D/A converter, that sort of thing). You can also use it as an interface with an iOS gizmo in class compliant mode.

Unlike the inexpensive Scarlett 2i2 Gen 2, this thing is a solid recording interface and the included EQ and effects in the routing software probably make it the world's best Podcast interface. That's what I'm going to use it for along with D/A conversion at my desk when it's not out making measurements.

Odds and Ends

Measurement gizmos used were the Audio Precision APx515, FIR Capture, Keysight U1282A and U1733C. The APx515 allows you to send or receive to/from a DUT through ASIO, thus allowing closed loop measurement of the analog inputs and outputs independently.

Phantom power is excellent, 47.3V unloaded and 13.4V when both channels have full 10mA loads. The spec for phantom is 48V +/-4V unloaded and 14V +/-1.2V loaded with 10mA. Most phantom powered mics I'm aware of draw 3mA to 5mA. The XL outputs are unaffected by the presence of phantom power. XL input impedance is 2,053Ω from 100Hz to 10kHz, sloping down to 1,850Ω at 100kHz. This impedance is the same with or without phantom power engaged as it should be. Optical digital I/O can do SPDIF or ADAT, MIDI I/O with an adapter cable is included as well. Metering is used for display feedback of operating adjustments as well as level indication. They are nicely visible, and like everything else on this unit, accurate.

Measurements

This unit has analog gain adjustments for both input and output, thus you should adjust both so that you can keep the digital signal as close to full scale as possible. I chose -3dBFS for these measurements.

Flat lines from a dual channel FFT measurement program called FIR Capture at all sample rates:

(http://soundscapesweb.com/files/PSW/RMEreview/Dual_FFT_Loopback.png)

Phase input and output:

(http://soundscapesweb.com/files/PSW/RMEreview/Phase_Input.png)

(http://soundscapesweb.com/files/PSW/RMEreview/Phase_Output.png)

Magnitude input and output:

(http://soundscapesweb.com/files/PSW/RMEreview/Magnitude_Input.png)

(http://soundscapesweb.com/files/PSW/RMEreview/Magnitude_Output.png)

Noise input and output:

(http://soundscapesweb.com/files/PSW/RMEreview/FFT_Noise_Input.png)

(http://soundscapesweb.com/files/PSW/RMEreview/FFT_Noise_Output.png)

Distortion at -3dBFS:

(http://soundscapesweb.com/files/PSW/RMEreview/THD_Input.png)

(http://soundscapesweb.com/files/PSW/RMEreview/THD_Output.png)

(http://soundscapesweb.com/files/PSW/RMEreview/IMD_SMPTE_Input.png)

(http://soundscapesweb.com/files/PSW/RMEreview/IMD_SMPTE_Output.png)

(http://soundscapesweb.com/files/PSW/RMEreview/IMD_DFD_Input.png)

(http://soundscapesweb.com/files/PSW/RMEreview/IMD_DFD_Output.png)

Finally, my Pin 1 torture test that few devices have ever passed. Passing is when the 60Hz square wave fundamental and harmonics stay below about -100dBFS. The Babyface Pro (why, oh why did they name it that?!), doesn't show any evidence that the square wave is on! The is a best ever result for me. No response whatsoever to a nasty 10V square wave shoved down Pin 1's throat. RME obviously got the memo and connected Pin 1 directly to chassis shared only with the negative power supply rail:

(http://soundscapesweb.com/files/PSW/RMEreview/Pin_1_FFT_Noise.png)

(http://soundscapesweb.com/files/PSW/RMEreview/Pin_1_RMS_Noise.png)
Title: Re: Measurement Interfaces
Post by: David Sturzenbecher on August 23, 2018, 08:33:46 pm
Meanwhile, on the other side of the railroad tracks...


Unlike the inexpensive Scarlett 2i2 Gen 2, this thing is a solid recording interface and the included EQ and effects in the routing software probably make it the world's best Podcast interface. That's what I'm going to use it for along with D/A conversion at my desk when it's not out making measurements.



Tell us more about your podcast...
Title: Re: Measurement Interfaces
Post by: Nathan Riddle on August 24, 2018, 10:09:55 pm
Hi Nathan:

I just did a little search and found a couple of interesting things about the Gen 1 unit:

1. It was spec'd to 96k max. Thus the (unusable IMO) 192k of Gen 2 is likely driver implemented without hardware upgrades.

2. Gen 1 now uses the Gen 2 driver (4.x series) with the same latency reduction. Maybe the Gen 1 driver (3.x series), which I can't find on the Net, would fix or reduce the phase error in the Gen 2 unit in exchange for increased latency.

It'll be fun if the mfg. fusses at me about these posts, but they won't. It'd put attention on things that would be better ignored from their POV.

So you think Gen1 and Gen2 hardware is same just a fresh look & newer driver?

I did have to update to 4.x driver for the G2 to work

I just so happen to have the 2.5.1 driver :)

https://www.dropbox.com/s/yfsy6tx7grvfb1t/focusrite-usb-2-driver-2.5.1.exe?dl=0


Edit: oh my goodness do NOT run G1 and G2 interfaces at the same time. Instant windows crash :(