Buy the M4 if you record a low-output dynamic, play keys, or want a published gain figure to plan against — it states 60 dB maximum mic gain, adds MIDI in and out, two extra line inputs and four outputs. Buy the M2 if you record one or two microphones, need no MIDI, and want the same -129 dB EIN preamps and ESS conversion for less money.
These two are closer than almost any pair on this site. Same ESS Sabre32 Ultra conversion, same full-color LCD metering on the front panel, same preamp design, same -129 dB-class EIN. If you are choosing between them on sound quality you are choosing on a non-issue. The decision is I/O, MIDI, and one specification gap that matters more than it looks.
The missing gain figure is the real difference
MOTU publishes -129 dB EIN for the M2, which tells you the preamp is quiet, and 115 dB of mic-input dynamic range, which tells you the converter is good. Neither tells you how much gain is available, and that is the number you need if your microphone is a broadcast dynamic.
An SM7B publishes -59.0 dBV/Pa. To know whether an interface can drive it you need to compare that against a maximum gain figure. The M4 gives you one: 60 dB, which is enough with no margin to spare. The M2 gives you nothing to compare against, so you are buying on reputation rather than on specification. In practice the M2 drives an SM7B for most voices; “in practice, for most voices” is not a plan, and this site does not estimate a figure a manufacturer declines to publish.
If that is your microphone, the honest recommendation is neither: a Focusrite Scarlett 2i2 publishes 69 dB, which is 9 dB of real margin. Best audio interfaces for the Shure SM7B is the full list.
What the M4's extra I/O is actually for
- Two extra line inputs, not two extra mic inputs. This is the most commonly misread thing about the M4. It is a four-input box with two microphone preamps. If you need four microphones, you need a different interface — see best audio interfaces for multiple mics.
- Four outputs instead of two. Useful if you run monitors plus a separate headphone amplifier, or monitors plus a hardware mixer. Wasted if you own one pair of speakers.
- MIDI in and out on 5-pin DIN. The one unambiguous win. If you play keys, this saves a separate interface, and class-compliant USB keyboards are not a complete substitute for DIN when older gear is involved. Best audio interfaces with MIDI ranks that field.
- Metering for all four channels rather than two, on the same LCD.
What both do better than most of the competition
The front-panel LCD metering is the feature that makes a MOTU worth considering at all. Seeing true input and output levels on the box, rather than alt-tabbing to a software mixer, changes how you work — it is the difference between noticing you are clipping and discovering it in playback. Combined with 120 dB of output dynamic range from the ESS conversion, these are the best-measuring boxes in their price band.
What neither has is any onboard voicing, DSP or compression. If you want character on the way in, that is the Universal Audio Volt family or the SSL 2+'s 4K switch. MOTU's position is that the signal path should be transparent, and both boxes deliver that.
Both MOTUs, plus the alternative
MOTU M4
Top pickMOTU · Four channels, MIDI and the best converters here
The pick if you want MOTU's conversion plus MIDI and a couple of extra line inputs. If you only ever record one or two microphones and do not need MIDI, the M2 does the same job for less.
Why it is here
- 60 dB of published gain and `-129 dBu` EIN is a genuinely quiet channel, and unlike the M2 the figure is published
- MIDI in and out on a box this size saves a separate interface if you play keys
- Full-color LCD metering for all four channels, which is more useful daily than any software mixer
What it costs you
- 60 dB is enough for an SM7B but without much headroom to spare
- Two of the four inputs are line-only, so it is not a four-microphone box
- No onboard voicing or DSP at all
MOTU M2
MOTU · The best converters and metering at the price
The pick if you care most about conversion quality and want to see your levels without alt-tabbing. If your mic is an SM7B and you want a published gain number you can check against the mic's sensitivity, the 2i2 is the safer buy.
Why it is here
- -129 dB EIN is genuinely quiet, and it shows on low-output dynamics
- Full-color LCD metering on the box is more useful day to day than any software mixer
- Independent phantom power and monitor switching per input
What it costs you
- MOTU does not publish a maximum mic-gain figure the way Focusrite does, so gain headroom is harder to plan around
- No onboard voicing or DSP at all
- Loopback needs the software, not a front-panel switch
Focusrite Scarlett 2i2 (4th Gen)
Focusrite · The most gain per dollar in a two-input box
The default answer for someone buying an SM7B or PodMic: it supplies enough clean gain that you never need a booster, which makes it the cheaper total purchase even when it is not the cheaper box. Look elsewhere only if you need MIDI or four outputs.
Why it is here
- 69 dB is the most gain of any interface at this price, and enough for an SM7B with headroom to spare
- 120 dB dynamic range means the converters are not the weak link
- Two inputs, so a second person does not mean a second purchase
What it costs you
- Air mode is a fixed voicing, not an EQ you can dial
- Plastic-and-metal build feels less solid than the SSL or Audient competition
- No MIDI, which matters if you also play keys
Which to buy
- One or two condensers or hot dynamics, no keys: the M2. You lose nothing audible and save real money.
- You play keys: the M4. MIDI I/O alone justifies the step.
- You run monitors and a separate headphone amp: the M4, for the four outputs.
- Your microphone is an SM7B, a PodMic or an RE20: neither, unless you specifically want MOTU's metering and accept 60 dB with no margin on the M4. A 69 dB box is the safer purchase.
