Motu M2 Review (Audio Interface)

[Adahn]

I'm surprised the M2's ADC SINAD is this low.

Here's the sinad specs as provided by the manufacturers:

Motu M line
Preamps: 97 dB
Line in (available only on M4): 106 dB

Scarlett 3rd Gen
Preamps: 98 dB
Line in: 94 dB

In the M2 review the preamp ADC sinad was measured, while in the M4 review the line in was used. Hence the discrepancy.

Measurements seem to confirm quoted specs. Nothing out of the ordinary here.

 

[bennetng]

oddly enough the M2 has the best filter I've seen in almost any all-in-one device

Disclaimer: my speculations, not necessarily correct. The tests were done with ASIO4ALL, if you see all other interfaces (non-DAC) measurements they were all done with dedicated ASIO drivers, including M4.

M2 also uses ES9016s.
https://prosound.ixbt.com/interfaces/motu-m2.shtml

Even higher-end chips can't achieve this level of steepness and attenuation.

As well as non-Pro chips:

You can see that the filter really struggled to achieve this level of steepness, which scarifies passband ripple and stopband attenuation.

But the filter shape looks pretty similar to the one on Windows mixer (the third screenshot):
https://www.audiosciencereview.com/...r-mirror-images-short-study.20318/post-674646

Windows mixer is "bad" when compared to something like SoX with 160dB+ attenuation, and when using non-integer resampling ratios, but it is more precise than typical on-chip filters which only use integer ratios. Played through Firefox rather than dedicated audio players to 100% avoid any potential hidden high quality SRC within the player.

That said, I tried ASIO4ALL on the Realtek but cannot reproduce the same result, it is only achievable when playing through Windows mixer. ASIO4ALL's built-in SRC performed pretty poor in my tests.

 

[Tks]

Disclaimer: my speculations, not necessarily correct. The tests were done with ASIO4ALL, if you see all other interfaces (non-DAC) measurements they were all done with dedicated ASIO drivers, including M4.


M2 also uses ES9016s.
https://prosound.ixbt.com/interfaces/motu-m2.shtml

Even higher-end chips can't achieve this level of steepness and attenuation.


As well as non-Pro chips:



You can see that the filter really struggled to achieve this level of steepness, which scarifies passband ripple and stopband attenuation.

But the filter shape looks pretty similar to the one on Windows mixer (the third screenshot):
https://www.audiosciencereview.com/...r-mirror-images-short-study.20318/post-674646

Windows mixer is "bad" when compared to something like SoX with 160dB+ attenuation, and when using non-integer resampling ratios, but it is more precise than typical on-chip filters which only use integer ratios. Played through Firefox rather than dedicated audio players to 100% avoid any potential hidden high quality SRC within the player.

That said, I tried ASIO4ALL on the Realtek but cannot reproduce the same result, it is only achievable when playing through Windows mixer. ASIO4ALL's built-in SRC performed pretty poor in my tests.

Yeah, that's the thing, for whatever reason, the M2's filter doesn't slope early like some of the Pro ESS chips' filters (while they do the proper filtering, they also have a slight downside of the cut-off starting a bit early at 19Khz to 20Khz before the wall really hits). The M2 (wish Amir could show us what it looks all the way down there) seems to not touch anything to 20Khz, and when it does brickwall, it does so properly, and deep as heck. There doesn't seem to be any appreciably worse byproducts either (maybe a wider spectrum would be needed to see if anything really nasty is occuring in the ultrasonic range perhaps?), but as is, the filter looks flawless from expectations out of the device of M2's cost..

I'm confused why the M4 doesn't have this, and of course, as stated prior, how no other filter that I've seen in a device does all of this at the same time (barring something like the Chord dedicated hardware with "million taps" ordeal). Not ESS, not Cirrus (granted I've not looked at these guys much), and certainly not AKM in any of their chips (4490, and 4499, no appreciable changes to filter choice, all pretty lazy).

 

[bennetng]

There doesn't seem to be any appreciably worse byproducts either (maybe a wider spectrum would be needed to see if anything really nasty is occuring in the ultrasonic range perhaps?)

It won't if the filter length is longer, apart from latency and intersample overs. On chip filters have fixed length so there must be some trade off in one or another. The M2 filter plot seems to have about 2x filter length than typical on-chip filters.

 

[Tks]

It won't if the filter length is longer, apart from latency and intersample overs. On chip filters have fixed length so there must be some trade off in one or another. The M2 filter plot seems to have about 2x filter length than typical on-chip filters.

So what's actually going on here? Is this filter exclusive somehow to the ES9016, and some weird magic is going on because the designer of said chip was bored or something? Or is there some dedicated hardware or processing going on besides the chip's filter itself as usually seen in basically every single other reviewed device to come across here?

 

[bennetng]

So what's actually going on here? Is this filter exclusive somehow to the ES9016, and some weird magic is going on because the designer of said chip was bored or something? Or is there some dedicated hardware or processing going on besides the chip's filter itself as usually seen in basically every single other reviewed device to come across here?

I suspect ASIO4ALL was routed to Windows mixer unexpectedly, as the test was not done using the dedicated MOTU driver.

 

[Tks]

I suspect ASIO4ALL was routed to Windows mixer unexpectedly, as the test was not done using the dedicated MOTU driver.

Wouldn't have ever suspected that to even be possible. Very interesting take, we should probably ask @amirm (for a future device) to try conducting a test to confirm this. Btw, what Windows version are you running. I see you at least have the Win 98 (or 95?) theme running pretty cleanly.

 

[bennetng]

Wouldn't have ever suspected that to even be possible. Very interesting take, we should probably ask @amirm (for a future device) to try conducting a test to confirm this. Btw, what Windows version are you running. I see you at least have the Win 98 (or 95?) theme running pretty cleanly.

Windows 7 with Aero turned off and retro theme.

 

[AnalogSteph]

Wouldn't have ever suspected that to even be possible.

Me neither. ASIO4All uses some pretty low-level APIs (kernel streaming), not sure how it could end up being routed through the entire sound stack.

 

[bennetng]

Me neither. ASIO4All uses some pretty low-level APIs (kernel streaming), not sure how it could end up being routed through the entire sound stack.

Some of my old posts regarding Kernel Streaming:
https://www.audiosciencereview.com/...p-vs-windows-volume-control.18360/post-605133

...and ASIO4ALL:
https://www.audiosciencereview.com/...-difference-in-sound-quality.7029/post-413398

The low-level part of Windows audio since Vista should be WaveRT. Kernel Streaming is a legacy (XP and older) API.
https://docs.microsoft.com/en-us/windows-hardware/drivers/audio/understanding-the-wavert-port-driver

 

[HelgenX]

Hello, I signed up just to ask a question about this unit, as I've had it for the past 3 weeks now. I came from a very old interface (Avid Mbox Mini 3 USB,) however, I understood that unit more as it felt more analog compared to digital. I feel like this Motu M2 is a bigger step up. Anyway, here's my question:

On this unit, it says it has two combo XLR/TRS ports, I'm aware of those, and know that they can take microphones or any other single line source. What I'm doing is simply plugging my turntable into the front ports, with the left side on the left and right side on the right. It's rather strange that even if I plug a single side in, it will still play sound on both sides. So I was thinking, these XLR/TRS ports, they're stereo on each side? Because if that's the case, couldn't I get a quarter inch female coupler and simply plug in to one port?

Reason I'm asking this is so that I don't have to adjust each side every time I plug my turntable in (so I can get the perfect balance.) Sorry if I sound confusing, and thanks for reading. I hope I can get an accurate response!

 

[Omid]

The XLR ports are mono. Have you pushed on the monitor button next to the input? If so the mono signal will be sent to both r and l channels.

 

[Omid]

Hello, I signed up just to ask a question about this unit, as I've had it for the past 3 weeks now. I came from a very old interface (Avid Mbox Mini 3 USB,) however, I understood that unit more as it felt more analog compared to digital. I feel like this Motu M2 is a bigger step up. Anyway, here's my question:

On this unit, it says it has two combo XLR/TRS ports, I'm aware of those, and know that they can take microphones or any other single line source. What I'm doing is simply plugging my turntable into the front ports, with the left side on the left and right side on the right. It's rather strange that even if I plug a single side in, it will still play sound on both sides. So I was thinking, these XLR/TRS ports, they're stereo on each side? Because if that's the case, couldn't I get a quarter inch female coupler and simply plug in to one port?

Reason I'm asking this is so that I don't have to adjust each side every time I plug my turntable in (so I can get the perfect balance.) Sorry if I sound confusing, and thanks for reading. I hope I can get an accurate response!

Can you explain your setup a bit. Do you have a preamp between the turntable and the motu (I’m guessing you don’t). If you don’t do you have a a step up transformer for impedance matching (because your cartridge may not play optimally at the impedance of the motu’s input).
if you use the trs input make sure the ring is disconnected for lower noise floor.

 

[Longshan]

The M2 is my interface/DAC of choice, replaced a Focusrite some time back. I get to drive my sub and Adam T7Vs off the XLR outs, and run my Axe Fx into the XLR ins. It's been great and I love the step of real VU meters over the light up rings.

You mean TRS outs?

I agree; I’m very happy with my M2.

 

[txbdan]

Hello, I signed up just to ask a question about this unit, as I've had it for the past 3 weeks now. I came from a very old interface (Avid Mbox Mini 3 USB,) however, I understood that unit more as it felt more analog compared to digital. I feel like this Motu M2 is a bigger step up. Anyway, here's my question:

On this unit, it says it has two combo XLR/TRS ports, I'm aware of those, and know that they can take microphones or any other single line source. What I'm doing is simply plugging my turntable into the front ports, with the left side on the left and right side on the right. It's rather strange that even if I plug a single side in, it will still play sound on both sides. So I was thinking, these XLR/TRS ports, they're stereo on each side? Because if that's the case, couldn't I get a quarter inch female coupler and simply plug in to one port?

Reason I'm asking this is so that I don't have to adjust each side every time I plug my turntable in (so I can get the perfect balance.) Sorry if I sound confusing, and thanks for reading. I hope I can get an accurate response!

They're mono inputs. You may need to hard pan them left and right to get proper stereo.

 

[GeorgeBynum]

The M2 has the look of other Motu products:

View attachment 109298

I like the color LED bar graphs as if you don't get sound, you know whether it is or is not getting to the product. Front panel sockets are for input sans the 1/4 headphone jack.

I find the overloaded input 2 and high outputs in general puzzling with nothing connected<big grin> Photoshop forever!

 

[Sentenza]

Hello,

I'm in the market for a 2 in / 2 out audio interface, to record a mic'ed guitar amp (via XLR input) and a digital piano (via 1/4" line input), and I'm a bit confused by the combo inputs of the Motu M2.

The combo inputs on the Motu M2 are labeled mic / line / guitar.
As with most interfaces in this price range, the mic input is on the XLR contacts, and the line and guitar inputs are both on the 1/4" contacts.
But as opposed to most other interfaces, the Motu M2 doesn't have a "hi-Z" or "instrument" button to switch between line input and guitar input.

My understanding is that on the other interfaces, the "hi-Z" button does two things: it changes the input impedance (to provide the high impedance required for guitars), and it changes the gain (to account for the lower signal level of guitars compared to line level).

Here with the Motu M2, the input impedance and the gain are the same for both line input and guitar input.

Motu M2 specs:

Line / guitar input​

- Impedance:1 MΩ (unbalanced input) / 2 MΩ (balanced input)​

- Max level in: +16 dBu (at min gain)​

- Gain range: 57 dB​

Example of another interface:
Scarlett 2i2 specs:

Guitar input:​

- Impedance: 1.5 MΩ​

- Max level in: +12.5 dBu (at min gain)​

- Gain range: 56 dB​

Line input:​

- Impedance: 60 kΩ​

- Max level in: +22 dBu (at min gain)​

- Gain range: 56 dB​

So, is it an issue to have such a high impedance for the line input on the Motu M2? And to have the same gain for line and guitar inputs?

If it is an issue, then what will be the practical implications when feeding the Motu M2 with a line signal, compared to other interfaces which have dedicated impedance value and gain for line input?

If it is not an issue, then why do the other manufacturers bother to offer different impedance and different gain between line and guitar inputs?

Thanks!

 

[Adahn]

So, is it an issue to have such a high impedance for the line input on the Motu M2? And to have the same gain for line and guitar inputs?

If it is an issue, then what will be the practical implications when feeding the Motu M2 with a line signal, compared to other interfaces which have dedicated impedance value and gain for line input?

If it is not an issue, then why do the other manufacturers bother to offer different impedance and different gain between line and guitar inputs?

Thanks!

Input impedance should be as high as possible to maximize signal. A factor of 10 is what we aim for usually. Line outs typically have an output impedance below 1k, so line in impedance is fine around 10k.

Going higher can make the input too sensitive, picking up more noise, so THD+N suffers as a result. Instrument inputs typically have worse THD+N because they're required to have a higher input impedance to accommodate the typically high output impedance of electric guitars.

If you compare the THD+N of the line input on the M2 and M4, you'll see a difference of about 6dB, both in the manual and amir's measurements. 106dB for the true line in versus 100dB for the combo one.

However, 100dB is still good enough. In comparison, the Scarlett's line in has a THD+N of 94 while the instrument input drops to 70. And even at 70 it's far from the worse I've seen for an instrument input.

 

[Omid]

Hello,

I'm in the market for a 2 in / 2 out audio interface, to record a mic'ed guitar amp (via XLR input) and a digital piano (via 1/4" line input), and I'm a bit confused by the combo inputs of the Motu M2.

The combo inputs on the Motu M2 are labeled mic / line / guitar.
As with most interfaces in this price range, the mic input is on the XLR contacts, and the line and guitar inputs are both on the 1/4" contacts.
But as opposed to most other interfaces, the Motu M2 doesn't have a "hi-Z" or "instrument" button to switch between line input and guitar input.

My understanding is that on the other interfaces, the "hi-Z" button does two things: it changes the input impedance (to provide the high impedance required for guitars), and it changes the gain (to account for the lower signal level of guitars compared to line level).

Here with the Motu M2, the input impedance and the gain are the same for both line input and guitar input.

Motu M2 specs:

Line / guitar input​

- Impedance:1 MΩ (unbalanced input) / 2 MΩ (balanced input)​

- Max level in: +16 dBu (at min gain)​

- Gain range: 57 dB​

Example of another interface:
Scarlett 2i2 specs:

Guitar input:​

- Impedance: 1.5 MΩ​

- Max level in: +12.5 dBu (at min gain)​

- Gain range: 56 dB​

Line input:​

- Impedance: 60 kΩ​

- Max level in: +22 dBu (at min gain)​

- Gain range: 56 dB​

So, is it an issue to have such a high impedance for the line input on the Motu M2? And to have the same gain for line and guitar inputs?

If it is an issue, then what will be the practical implications when feeding the Motu M2 with a line signal, compared to other interfaces which have dedicated impedance value and gain for line input?

If it is not an issue, then why do the other manufacturers bother to offer different impedance and different gain between line and guitar inputs?

Thanks!

The impedance is lower on the XLR connection. Have a look at the attached image.

 

[Sentenza]

The impedance is lower on the XLR connection. Have a look at the attached image.

Thanks, yes I know, actually this raises another question:

The microphone that I will be using is a Sennheiser E906, which has an impedance of 350 Ω.

My understanding is that the mic preamp should have an input impedance of at least 10 times the mic impedance.

The input impedance of the Motu M2 is 2650 Ω, which is "only" 7.5 times higher.
The input impedance of e. g. the Scarlett 2i2 is 3000 Ω, which is 8.5 times higher.

So the Scarlett 2i2 is still below the 10x ratio, but is above the Motu M2 (8.5x vs 7.5x).
Should this difference make me want to choose the Scarlett 2i2 over the Motu M2?