This and That:
Basic black cardboard box with Pai Audio logos. The same that is also used for the DR1, MR2 and MR3.
Same accessories as well. Only a soft pouch and no hard case, which is inappropriate for the price of the MR4.
The cable is the same one, too, and lacks a chin-slider. Not very supple.
Good build quality.
Dual-bore design with dedicated dampers; protective mesh at the end of the nozzle. Visible drivers, crossover components and acoustic routing, which I like.
Sound:
Low impedance sources, largest included silicone tips.
Tonality:
In short, I would describe the MR4 as having a relatively balanced and natural tonality with a quite smooth and easy-going character. It is just moderately on the warmer and bassier side of neutral (ER-4S and UERM as reference).
So yeah, I would say the MR4 sounds mostly like the Pai Audio MR3 from the lows to the midrange but lacks the MR3’s treble brightness and is noticeably more even and smoother sounding up there.
Bass quantity is spot-on identical to the MR3 which has got about 5 dB more bass than my ER-4S and ca. 2 dB more than my UERM. So it has got a still fairly neutral lower end that is quite similar to that of my InEar StageDiver SD-2 and the Jays q-JAYS, so there is enough impact so that the in-ear does not sound too sterile or flat, but is still mostly balanced and natural sounding in the lows.
The lows’ emphasis starts to climb somewhere around 500 Hz and reaches its climax around 180 Hz. From there on, it extends flat down to 45 kHz and rolls somewhat off down to 20, which makes its lower end sound and measure exactly as that of the MR3, except for that the MR3 measures to have just slightly more sub-bass quantity.
The mids are then pretty much neutral and flat sounding, with just a very slight hint of warmth due to the lower and lower middle root lift.
Between 1.5 and 5 kHz, level is evenly somewhat in the background, giving bright voices a fatigue-free yet not too relaxed or dark character.
Above 5 kHz, the level comes back broadly around 6 kHz but is still a bit relaxed, somewhat below zero.
Around 8 to 9 kHz, I can spot a minor elevation past zero.
Past 12 kHz, the super treble rolls off, so here could be a little more subtle sparkle above 10 kHz, but I don't really miss anything.
So yeah, basically an MR3 with a relaxed and smoother sounding central treble and less brightness, and slightly darker upper mids.
Resolution:
The bass is pretty tight, quick and features good control, just like most other multi-BA in-ears in this price range with non-vented woofers.
The treble sounds adequately detailed and especially very even and natural. Still, compared to other multi-BA in-ears around and below $400, the MR4's highs appear somewhat less differentiated and refined - including the cheaper MR3 that appears more resolving and better, more cleanly differentiated in the highs; just more refined overall.
While the mids are tonally really good, they appear somewhat veiled. Certainly not bad and not blunt yet, but in terms of midrange details, other comparably priced in-ears are ahead, including the MR3 and my Logitech UE900. While speech intelligibility is good, the MR4's mids appear veiled, as if they were behind a thin and translucent curtain.
Soundstage:
What I am happy to hear is that the MR4 has adopted a key feature of Pai Audio’s other multi-BA in-ears: its soundstage is really good and does not only feature pronounced spatial width but also a decent amount of depth and sounds precise, with good separation, but it especially especially the high authenticity that makes it stand out from the rest, as only very few comparatively priced in-ears (such as my InEar StageDiver SD-2 and Audio Technica ATH-IM03) sound as three-dimensional and spatially convincing, realistic, as the MR4 does.
Compared to that of the MR3, the MR4’s soundstage has got more spatial width and a little less depth but still layers nicely.
Instrument placement and separation as well as three-dimensionality are really good and generate the impression of a very authentic spatial presentation. The soundstage’s airiness and the generated air/empty space around instruments help with that as well.
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Compared to other Multi-BA In-Ears:
Pai Audio MR3:
Both have the same shells, accessories and cables.
Both have got mostly similar bass quantity and extension but the MR3 appears slightly less bassy as its treble is more forward.
In the mids, the MR4 sounds just very minimally warmer/darker but a slight bit less distanced than the MR3.
The MR3 is brighter in the treble and extends somewhat better above 10 kHz but the MR4 is more even and therefore smoother and more coherent sounding in the treble in comparison.
Both have similar bass quality and control whereas the MR3’s mids are a bit more detailed. When it comes to the treble, the MR3 appears a little more differentiated and separated as well.
The MR4 has got the somewhat wider soundstage while the MR3’s is a little deeper. Both are however identically precise and especially authentic.
Logitech UE900:
The UE has got the superior cables as well as accessories.
Both head into a more or less comparable tonal direction.
Both have got about similar bass quantity but the UE does not roll off in the true sub-bass whereas the MR4 does slightly.
In the mids, the UE appears a little skewed and tilted to the darker side whereas the MR4 seems more realistic in comparison.
In the middle treble around 5 kHz, the UE is a bit more relaxed but has got the brighter, more sparkling upper treble.
In terms of bass quality, the MR4 has got the slightly quicker attack while both are equally controlled.
In the mids, while the MR4 is tonally more correct, the UE900 is slightly more detailed although its midrange’s details also slightly lack behind its bass and treble.
In the treble, the UE appears a bit better differentiated and layered than the MR4.
However, when it comes to soundstage, the MR4’s is wider, has got more depth and is also better layered and has got the superior separation while the UE’s appears a bit more compact and lacks depth in comparison and does not sound as precise or authentic.
Fischer Amps FA-3E:
The FA-3E has got the superior accessories and cables.
The FA-3E is ultimately somewhat more neutral, with slightly less bass quantity. The MR4 is somewhat warmer in the root/lower mids.
In the mids, the Fischer Amps sounds a little brighter than the slightly warm MR4.
In the treble, the MR4 is somewhat more relaxed and smoother sounding, except for directly around 5 kHz where the FA-3E is more relaxed.
The MR4’s bass is a little quicker while in-ears are comparatively controlled.
In the mids, the Fischer Amps appears a just slightly more detailed, but in the treble, the Pai Audio is somewhat more refined and differentiated.
While the FA-3E has got a pretty nice and well-rounded soundstage from what I perceive, the MR4’s is somewhat wider and also a little deeper. The Pai Audio’s stage is also better layered and somewhat more differentiated with the ultimately higher authenticity and better portrayal of emptiness around instruments.
Conclusion:
The Pai Audio MR4 sounds smoother and more relaxed in the treble than the MR3, however the MR3 resolves better in the mids and highs and offers the slightly more circular soundstage. And it costs less.
MR3 over MR4? Definitely yes.