• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

Motu M4 Audio Interface Review

lizhuoyin

Active Member
Forum Donor
Joined
Dec 26, 2020
Messages
187
Likes
99
Location
NH
Motu 4 ADC results being better than Motu 2 ADC (104 dB vs 96 dB) is simply because other conections in the back on the M4 were used for connecting instead of the front ones on the M2, yes ?

But microphones can't be connected to M4 back yes ? So between M2 & M4 for microphone usage there would be no difference ?

Are my assumptions corect ?
I can get:
THD+N @106.5 from LINE OUT 3 to LINE IN 3 with -1 dBFS sine.
THD+N @104 from LINE OUT 3 to front IN 1 (TRS, minimal gain) with -7 dBFS sine.
THD+N @100 from LINE OUT 3 to front IN 1 (XLR, minimal gain) with -10 dBFS sine.
 

umbral

Member
Joined
Apr 4, 2021
Messages
76
Likes
31
In recording, the ADC is not the limiting factor in audio input quality as much as the noise performance of the microphone inputs, which Amir did not characterize. However, I can tell you from experience that the noise performance of the m4 is good enough to record with insensitive dynamic microphones easily, if that is your concern. Think about it, the ADC test uses an ultra clean, low distortion, low noise signal, and then digitizes it. What recording sources do you have that can perform at that level of noise and distortion? Mics have self noise, musical instruments have all kinds of noise and distortion, etc. I wouldn't get hung up on ADC quality.

I have used a few inexpensive wired and portable interfaces for recording at quiet levels with insensitive mics, and the m4 is the best of them.

Thank you very much your explanations.
I was trying to decide between M4 & M2, but it looks like M2 is enough for my needs. I won't notice anything different compared to M4 in terms of microphone quality recordings.

I will be getting this small but extremely flat condenser microphone (electret), that is a very good priced sub-cardioid (slightly wide cardioid) : http://www.lineaudio.se/CM4.html I will be using it for vocals, yes, since it is very flat and very easy to EQ later if one desires a certain style. But It also sits extremely well in the mix without any EQ.

From the producer of the microphone : "The CM4 is not sensitive to amplifier and cable load, which makes the differences smaller. " (between interfaces)

Yes, the M4 rear line inputs bypass the preamp, that's why they're cleaner.

You can't connect a mic directly to the rear line inputs. If you have a dedicated mic preamp / channel strip, then you could use the rear input for mics.

Otherwise the front mic inputs should be the same.

Thank you very much for the knowledge.
So the M2 is fine and there is no need for M4 it seems...
 

lizhuoyin

Active Member
Forum Donor
Joined
Dec 26, 2020
Messages
187
Likes
99
Location
NH
I will be getting this small but extremely flat condenser microphone (electret), that is a very good priced sub-cardioid (slightly wide cardioid) : http://www.lineaudio.se/CM4.html I will be using it for vocals, yes, since it is very flat and very easy to EQ later if one desires a certain style. But It also sits extremely well in the mix without any EQ.

From the producer of the microphone : "The CM4 is not sensitive to amplifier and cable load, which makes the differences smaller. " (between interfaces)
My kids' piano teacher got these line mics for piano recording. He likes its neutrality.
 

umbral

Member
Joined
Apr 4, 2021
Messages
76
Likes
31
I can get:
THD+N @106.5 from LINE OUT 3 to LINE IN 3 with -1 dBFS sine.
THD+N @104 from LINE OUT 3 to front IN 1 (TRS, minimal gain) with -7 dBFS sine.
THD+N @100 from LINE OUT 3 to front IN 1 (XLR, minimal gain) with -10 dBFS sine.

Thank you for the information.
If you use line out 1-2 instead of 3-4 out, would you reach around 96 dB like they did with the M2 ?
 

lizhuoyin

Active Member
Forum Donor
Joined
Dec 26, 2020
Messages
187
Likes
99
Location
NH
Thank you for the information.
If you use line out 1-2 instead of 3-4 out, would you reach around 96 dB like they did with the M2 ?
I don't think that matters, right? We are testing the inputs. It should have nothing to do with sources/outputs.
 

umbral

Member
Joined
Apr 4, 2021
Messages
76
Likes
31
My kids' piano teacher got these line mics for piano recording. He likes its neutrality.

Yey that's great, that sounds so much fun, i am actually still waiting for the microphone to be made and arrive, but i know from others that they are extraordinary, and can be used for vocals instead of the usual Large Condensers Microphones.

In mixing music with vocals, the vocals with this microphone will sit very well, unlike many other microphones that sound bright or harsh and overlap with the normal sounds in a bad way and that requires lots of EQ.

I don't think that matters, right? We are testing the inputs. It should have nothing to do with sources/outputs.

The outputs should not matter, correct. Or do you think they could affect in any way the results ?

Since there is no practical way to avoid using the front inputs for microphone, only by using separate microphone amplifier as @sharpty said with M4, only then i could use the rear input for mics. But that itself would degrade the signal a little bit i suppose too ? Maybe a more expensive external amplifier compared to the ones in M4 & M2 would result in better ADC, i suppose.

lizhuoyin do you think that M4 has in any way a better ADC for front inputs compared to M2 ?
 
Last edited:

sharpty

Member
Joined
Jan 11, 2019
Messages
76
Likes
96
Location
Queen City
If you use line out 1-2 instead of 3-4 out, would you reach around 96 dB like they did with the M2 ?
I think Amir was testing the M2 ADC at the verge of clipping, and distortion rises before clipping. In @lizhuoyin's test, the input was measured at -7dBFS, closer to the sweet spot.

1618519079245.png

EDIT: Maybe I'm not interpreting this correctly though. lol
 
Last edited:

lizhuoyin

Active Member
Forum Donor
Joined
Dec 26, 2020
Messages
187
Likes
99
Location
NH
The outputs should not matter, correct. Or do you think they could affect in any way the results ?
Yes, you are correct. Theoretically, you can use other sources to output test signal (like Amir did) to test M4 input performances as long as the source has lower THD+N. I just found it's convenient to use M4 own LINE OUT 3 as source since its THD+N is better than any of M4's inputs. That's another benefit to buy M4 for testing.
 

adg

Member
Forum Donor
Joined
Oct 14, 2020
Messages
44
Likes
91
I've been testing both the Motu M4 and Audient iD14 mkII for the last few days, and I'll post some of my usability/functionality feelings soon. I'm not going to be able to speak to recording or audio quality as I haven't done any recording yet, and I don't think I'd distinguish a sound difference by ear, but hopefully my hands on observations might help someone on the fence between these two units.
 

Attachments

  • IMG-8348.jpg
    IMG-8348.jpg
    881.9 KB · Views: 236

lizhuoyin

Active Member
Forum Donor
Joined
Dec 26, 2020
Messages
187
Likes
99
Location
NH
1618527655949.png


Testing LINE IN 3 performances using REW. Measurements were performed while connecting M4 LINE OUT 3 to LINE IN 3 with TRS cable.
Does this mean there is no ESS hump? Correction: This graph is not about SMPTE/DIN vs. dBFS. So cannot tell if ESS hump exists or not.
 
Last edited:

umbral

Member
Joined
Apr 4, 2021
Messages
76
Likes
31
I've been testing both the Motu M4 and Audient iD14 mkII for the last few days, and I'll post some of my usability/functionality feelings soon. I'm not going to be able to speak to recording or audio quality as I haven't done any recording yet, and I don't think I'd distinguish a sound difference by ear, but hopefully my hands on observations might help someone on the fence between these two units.


Was disappointed that without type C the ID14/4 MKII has very low headphone output below first generation. @ 14:00

OK, so to me this is a huge disappointment, as seen in your measurements. The ID MKII in reality doesn't even reach MK1 power levels on headphones in mW with Type A. The values drop to abysmal levels far below MK1. They should have used the USB cable to transfer data to a PC or Laptop and power the unit using a power brick. To me this is beyond comprehension what these companies are thinking when designing a product.

Also you can activate English subtitle on this video :


You can see there is a big difference in terms of sound styles, as far as he describes them. The Motu is darker, the Audient is Lighter.

What i didn't like about Audient is that for example in this video with the first generation the converters after "500 round trip test" show how bad they are despite their marketing compared to SSL2.

Both these things make me lean towards Motu M2 or M4 depending on what needs one may have. M4 is +35% more expensive than M2.

 
  • Like
Reactions: adg

617

Major Contributor
Forum Donor
Joined
Mar 18, 2019
Messages
2,403
Likes
5,296
Location
Somerville, MA
I would recommend making a choice based on feature set, usability, price, warantee and performance in that order. The reasons I like the m4 have nothing to do with audio performance.
 

adg

Member
Forum Donor
Joined
Oct 14, 2020
Messages
44
Likes
91
I would recommend making a choice based on feature set, usability, price, warantee and performance in that order. The reasons I like the m4 have nothing to do with audio performance.

I chose the Audient iD14 and Motu M4 specifically because both have a line out I can use to hook up my Bottlehead Crack headphone amp.

I’ll post the pros and cons I see between the units tomorrow or over the weekend.
 

umbral

Member
Joined
Apr 4, 2021
Messages
76
Likes
31
The M4 has a monitoring knob, where you can blend between input and playback.


Monitoring using software instead of hardware means that one can apply many effects (reverb, guitar modeling etc.) to the live signal.


Can you reproduce this blending thing that the knob does in your software ?
Is there any benefit for the knob on M4 compared to M2 that does not have it ?

How can you duplicate the functionality of the knob in software such as Presonus Studio One 5.2 ?
Would there be any benefit of M4 vs M2 on this matter ?

Does this affect in any way or makes it easier during loop-back to have this knob ?
 
Last edited:

adg

Member
Forum Donor
Joined
Oct 14, 2020
Messages
44
Likes
91
I'll write my full M4 vs iD14 mkII thoughts later, but I'm going to return the iD14 and keep the Motu 4 minimally for the reason that the M4 has a physically limited and clear volume knob that you can always see what it's set to.

I've had an issue with the iD14 not being recognized after my Windows 10 machine goes to sleep, and I have to unplug and re-plug in the id14 for it to show up in my sound devices. I just tried playing Spotify for the first time today and somehow the volume output was insanely loud. I had to immediately pause Spotify and hope there was no damage done to my 8030Cs. I'm not sure why the volume was maxed out, but the inability to see the current volume on the iD14 without actually adjusting the volume briefly or looking at the mixer is a deal breaker for me, and something that isn't an issue with the M4.

The iD14 volume knob can perform other actions, which might be a perk for some, but I'll take the M4's dedicated volume knob.
 

umbral

Member
Joined
Apr 4, 2021
Messages
76
Likes
31
I'll write my full M4 vs iD14 mkII thoughts later, but I'm going to return the iD14 and keep the Motu 4 minimally for the reason that the M4 has a physically limited and clear volume knob that you can always see what it's set to.

I've had an issue with the iD14 not being recognized after my Windows 10 machine goes to sleep, and I have to unplug and re-plug in the id14 for it to show up in my sound devices. I just tried playing Spotify for the first time today and somehow the volume output was insanely loud. I had to immediately pause Spotify and hope there was no damage done to my 8030Cs. I'm not sure why the volume was maxed out, but the inability to see the current volume on the iD14 without actually adjusting the volume briefly or looking at the mixer is a deal breaker for me, and something that isn't an issue with the M4.

The iD14 volume knob can perform other actions, which might be a perk for some, but I'll take the M4's dedicated volume knob.

Bad drivers. Audient doesn't have good drivers at all. Thank you for confirming this issue.
If you use Presonus Studio One for example and use their Atom SQ super controller, you can do anything and you no longer need the dual purpose volume knob of the ID14 : https://www.presonus.com/products/ATOM-SQ
 

617

Major Contributor
Forum Donor
Joined
Mar 18, 2019
Messages
2,403
Likes
5,296
Location
Somerville, MA
The M4 has a monitoring knob, where you can blend between input and playback.


Monitoring using software instead of hardware means that one can apply many effects (reverb, guitar modeling etc.) to the live signal.


Can you reproduce this blending thing that the knob does in your software ?
Is there any benefit for the knob on M4 compared to M2 that does not have it ?

How can you duplicate the functionality of the knob in software such as Presonus Studio One 5.2 ?
Would there be any benefit of M4 vs M2 on this matter ?

Does this affect in any way or makes it easier during loop-back to have this knob ?

Real time monitoring is extremely useful for recording voice and real musical instruments, where a small amount of latency can be distracting. Latency is dependent on your computer, applied effects, and the audio interface as well. In my experience, the latency of the M4 is low enough to record guitars with effects without a problem, and speech with effects is ok too. It's fine for VST instruments controlled by a keyboard as well.

You can't duplicate the real time monitoring with your computer as the whole point of the real time monitoring is that it is the signal direct from the inputs, not going to and from your computer.
 

umbral

Member
Joined
Apr 4, 2021
Messages
76
Likes
31
Real time monitoring is extremely useful for recording voice and real musical instruments, where a small amount of latency can be distracting. Latency is dependent on your computer, applied effects, and the audio interface as well. In my experience, the latency of the M4 is low enough to record guitars with effects without a problem, and speech with effects is ok too. It's fine for VST instruments controlled by a keyboard as well.

You can't duplicate the real time monitoring with your computer as the whole point of the real time monitoring is that it is the signal direct from the inputs, not going to and from your computer.

OK i fully agree with you.

Is there an alternative to the knob on the M4, if i buy the M2 ? Basically with M4 you can blend from Input (to hear only what i sing/play) to playback (full track sound including what i sing/play).

If i want to use the headphones on M2 for monitoring, i can only adjust the headphones volume, no also blending like on M4.

Can this blending be done using software ? Or i must simply reduce the volume of every single track in software except the vocal one i am recording ? Or just solo the track from the software will do the same thing as the knob being fully to input position on M4 ? Everything in between means i need to lower everything down manually except the vocals, yes ?

What is the most used situation normally when singing/playing ?
I am trying to see if that knob alone and two inputs/outputs (that i may never use since they are fixed volume), deserves +35% price compared to M2.

Do you find the blending useful or do you always go either full track or solo (and mute rest) when you are singing/playing ?
 

617

Major Contributor
Forum Donor
Joined
Mar 18, 2019
Messages
2,403
Likes
5,296
Location
Somerville, MA
OK i fully agree with you.

Is there an alternative to the knob on the M4, if i buy the M2 ? Basically with M4 you can blend from Input (to hear only what i sing/play) to playback (full track sound including what i sing/play).

If i want to use the headphones on M2 for monitoring, i can only adjust the headphones volume, no also blending like on M4.

Can this blending be done using software ? Or i must simply reduce the volume of every single track in software except the vocal one i am recording ? Or just solo the track from the software will do the same thing as the knob being fully to input position on M4 ? Everything in between means i need to lower everything down manually except the vocals, yes ?

What is the most used situation normally when singing/playing ?
I am trying to see if that knob alone and two inputs/outputs (that i may never use since they are fixed volume), deserves +35% price compared to M2.

Do you find the blending useful or do you always go either full track or solo (and mute rest) when you are singing/playing ?

Generally full on or off. In some cases, like with a midi controlled instrument, there is no 'real time' signal to hear.
When you record your voice or instrument in your DAW, you can monitor it in any number of ways, adjusting volume, effects, eq and so on. However, it will not be real time, and latency will increase in proportion to the number of effects applied. Having said that, latency is quite good with the m4, and I'd expect it's good enough with the m2 that you don't need the real time monitor knob at all. I rarely use the real time knob.
 

adg

Member
Forum Donor
Joined
Oct 14, 2020
Messages
44
Likes
91
Do any M4 owners have any issues with volume jumps from barely turning the monitor output volume knobs?

I usually find that around 9pm on the volume knob is a bit quieter than I'd like, but then turning the knob just a tiny bit is a bit too loud while I'm at my work from home desk. After the "bit too loud" position of the volume knob, it seems like the control is a bit more reasonable when I start listening at louder volumes. It's almost like there's an irregular volume bump on what I'd otherwise expect to be a linear volume increase.

I don't have this issue with the Audient iD14 mkII I am testing, which I believe goes up 2db per rotational click on the knob. The iD14 uses a multifunction free rotating knob in place of a potentiometer.
 
Top Bottom