This is a review and detailed measurements of the MOTU M6 professional audio interface. It is on kind loan from a member and costs US $400 as of this writing.
The layout is clean as you see although that comes at the cost of not having input selection type (that is decided based on cable connection type -- see below). The LED have a grainy look to them but otherwise, nicely indicate clipping. Interesting to see dual headphone out, implying good drive capability. We will test this.
Power is provided through a 15 volt, 0.5 amp adapter (NOT USB):
It is unclear whether the achieved DNR and THD+N are at the max levels indicated or some other.
MOTU M6 DAC Measurements
Two outputs are provided: Line Out and Monitor Out. Later is impacted based on volume position. Performance was the same in both so I stayed with Monitor Out so I could adjust the levels as needed:
I read the spec as distortion and noise being down 110 dB which my measurements show to be conservative. As is, performance is very good for an interface:
We can sweep the input to find the best performance range:
So the +16 dBu spec is confirmed.
Here is the dynamic range:
This gives us the 120 dB number given in the spec.
Multitone distortion is extremely good for an interface and in general:
IMD is very good as well:
As is jitter:
Same for linearity:
Filter is as expected but with better attenuation > 24 kHz as I expected:
As a result, wideband THD+N measurement results are good for class:
MOTU M6 ADC Measurements
DAC measurements went well seeing how we essentially achieved company specs. The situation reversed itself for input/ADC side. I used TRS cable as indicated which gave me 6 dB lower gain which was well needed. But when I fed the M6 a 4 volt signal and adjusted its gain to near 0 dBFS, I got severe distortion with SINAD dropping to just 39 dB! Backing off to -3.5 dB, regained fair amount of distortion:
We can see the issue here as I sweep the levels:
As you see, the input starts to saturate at around -10 dBFS. Going with the dashboard value, performance is good but could be better had this not been an issue:
Which is sadly worse that MOTU M4.
IMD test confirms the same saturation issue:
At least we are able to kind of get to +18 dBu spec, albeit with a lot of distortion.
Here is our dynamic range:
Finally, response is more or less frequency independent:
EDIT: Line In 5 & 6 seem to have better specs so let's measure that:
Line In 5 & 6 ADC Measurements
18 dBu signal still causes saturation but not as bad as the combo inputs:
Backing off to our standard 4 volts input, gets us much better results:
Resulting in performance now matching the Motu M4:
We are still shy of the spec but if we sweep, we find that we can actually beat the it by a bit near clipping:
There is no improvement in dynamic range as predicted in above graph:
So if you are willing to give up the trim controls, you can do better with Lines In 5 and 6 inputs.
MOTU M6 Headphone Amplifier Measurements
Headphone output is usually an after taught in many interfaces and such is the case here:
Conclusions
I was very hopeful that we had a good interface in our hands after testing the DAC. A number of issues I am used to seeing in MOTU interfaces were ironed out. Alas, the ADC performance was not able to keep up with the DAC. Seeing how this is the main job of an interface, I am somewhat disappointed although what it delivered is not too bad if you stay well away from 0 dBFS. Headphone output was not too bad at high impedance but awful with low.
I am going to recommend the MOTU M6 based on its reasonable price and doing well on DAC tests. It could have gotten higher rating if a bit more care was put in the ADC (or better specification on how to achieve their numbers).
------------
As always, questions, comments, recommendations, etc. are welcome.
Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
The layout is clean as you see although that comes at the cost of not having input selection type (that is decided based on cable connection type -- see below). The LED have a grainy look to them but otherwise, nicely indicate clipping. Interesting to see dual headphone out, implying good drive capability. We will test this.
Power is provided through a 15 volt, 0.5 amp adapter (NOT USB):
| Connector type | Dynamic range (A-weighted) | THD+N (unweighted) | Max level | |
|---|---|---|---|---|
| Line Output | 1/4" TRS, balanced, tip hot | 120 dB | -110 dB | +16 dBu |
| Line Input | 1/4" TRS, bal/unbal, tip hot | 115 dB | -107 dB | +18 dBu |
| Mic input | XLR, balanced, pin 2 hot | 115 dB | -129 dBu EIN | +10 dBu (at minimum gain) |
| Phones | 1/4", TRS stereo | 115 dB | -110 dB | +12.5 dBu |
It is unclear whether the achieved DNR and THD+N are at the max levels indicated or some other.
MOTU M6 DAC Measurements
Two outputs are provided: Line Out and Monitor Out. Later is impacted based on volume position. Performance was the same in both so I stayed with Monitor Out so I could adjust the levels as needed:
I read the spec as distortion and noise being down 110 dB which my measurements show to be conservative. As is, performance is very good for an interface:
We can sweep the input to find the best performance range:
So the +16 dBu spec is confirmed.
Here is the dynamic range:
This gives us the 120 dB number given in the spec.
Multitone distortion is extremely good for an interface and in general:
IMD is very good as well:
As is jitter:
Same for linearity:
Filter is as expected but with better attenuation > 24 kHz as I expected:
As a result, wideband THD+N measurement results are good for class:
MOTU M6 ADC Measurements
DAC measurements went well seeing how we essentially achieved company specs. The situation reversed itself for input/ADC side. I used TRS cable as indicated which gave me 6 dB lower gain which was well needed. But when I fed the M6 a 4 volt signal and adjusted its gain to near 0 dBFS, I got severe distortion with SINAD dropping to just 39 dB! Backing off to -3.5 dB, regained fair amount of distortion:
We can see the issue here as I sweep the levels:
As you see, the input starts to saturate at around -10 dBFS. Going with the dashboard value, performance is good but could be better had this not been an issue:
Which is sadly worse that MOTU M4.
IMD test confirms the same saturation issue:
At least we are able to kind of get to +18 dBu spec, albeit with a lot of distortion.
Here is our dynamic range:
Finally, response is more or less frequency independent:
EDIT: Line In 5 & 6 seem to have better specs so let's measure that:
Line In 5 & 6 ADC Measurements
18 dBu signal still causes saturation but not as bad as the combo inputs:
Backing off to our standard 4 volts input, gets us much better results:
Resulting in performance now matching the Motu M4:
We are still shy of the spec but if we sweep, we find that we can actually beat the it by a bit near clipping:
There is no improvement in dynamic range as predicted in above graph:
So if you are willing to give up the trim controls, you can do better with Lines In 5 and 6 inputs.
MOTU M6 Headphone Amplifier Measurements
Headphone output is usually an after taught in many interfaces and such is the case here:
Conclusions
I was very hopeful that we had a good interface in our hands after testing the DAC. A number of issues I am used to seeing in MOTU interfaces were ironed out. Alas, the ADC performance was not able to keep up with the DAC. Seeing how this is the main job of an interface, I am somewhat disappointed although what it delivered is not too bad if you stay well away from 0 dBFS. Headphone output was not too bad at high impedance but awful with low.
I am going to recommend the MOTU M6 based on its reasonable price and doing well on DAC tests. It could have gotten higher rating if a bit more care was put in the ADC (or better specification on how to achieve their numbers).
------------
As always, questions, comments, recommendations, etc. are welcome.
Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
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