InEar StageDiver SD-4 (Small)


500+ Head-Fier
Pros: Great fit, intimate sound, very natural and organic tonality. Great live sound.
Cons: I love bass and balanced armature drivers can't match a good dynamic driver imho
Just to give a little background, this is my first review for head-fi. I have been a relatively active member now for a few years since joining way back when circa 2009 when I was teaching English in Japan. My first foray discussing all things headphone with fellow headfi’ers convinced me then to pair a new AKG k450 with my Cowon X5, and ever since I have pursued a mission of smooth highs which has ultimately taken me away from bass and more towards neutrality. I moved from my x5/k450 setup to a Cowon J3 and the Etymotic HF5 , then a Samsung S3/Apex Glacier dac/amp to the classic ER4S. But recently I have been searching for a more immersive experience on the go, having sold off most of my home rig due to lack of use. I still have my trusty HD650s under my bed and still hold them as a benchmark for the kind of sound I love. However time is time and money is money and with a job requiring a lengthy commute by train I am firmly in IEM land for now.
From SD-2 to SD-4
I moved away from the ER4S neutrality (albeit conservatively), buying a pair of Stagediver SD-2 iems last October.  I really enjoyed the nice bump in their bass over the ER4S and the more 3D soundstage and more balanced all-round presentation. But I still found myself thinking of the nice, more laid back bassy and immersive sound of my HD650s. I have enjoyed talking with the community on the SD-2/SD-3 thread and heard about Inear’s new SD-4, a 4 driver 2 way iem. Billed as a Stagediver with a more holographic and bassy sound than the SD-2, I was eager to try it out. On a whim I emailed Marco from Inear and he was willing to send me an SD-4 for review. Lucky me!
Build Quality
Compared to the SD-2 the SD-4 on first glance is quite similar in appearance. Its shell, accommodating an extra two drivers is surprising compact, and is only slightly thicker across compared to its smaller brother. Also Inear have now moved to a black cable for all their models, as the previous clear cable (which I have on my SD-2s) turns green after a while due to natural oxidation processes. Personally I do not mind the change in colour but the black cable did look quite smart and less conspicuous so I can perfectly understand the reasoning behind the change. Also one definite improvement in build quality between my own SD-2 and the SD-4 is at the joint where the sound nozzle enters the iem main body. On my SD-2 the surface is ridged yet on the SD-4 it is totally smooth. Not an imperative feature but it is nice to see Inear striving for perfection in their products.
The SD-4 come with nearly all the same accessories I had with my SD-2. You get a nice sturdy Pelican carrying case, a zipbag with some cleaning wipes, a mini-jack adaptor for use with larger amps and of course an assortment of tips. For the purposes of the review Marco sent me the spare filters as seen in the photo. These are an extra you can purchase from Inear’s website directly. With my ER4S I waited a year to change the filters that come with that iem, and yes the change does make a sonic difference. The year long care I gave them (even taking a cue from Tyll Hertsens to use Japanese wax cleaners) could not stop some microscopic debris or dust from gathering over the grill. So getting some spare filters are a good idea in the long term imo.
The Sound
In a word, the SD-4s sound ‘natural’. Another word could be ‘immersive’. Some other descriptors could be ‘front row’, ‘in the mix’, ‘just put them in and forget they are there’, and the Michael Mercer classic ‘they just bring you closer to the music’.
So all very good things! All which distinguish the SD-4 hugely from its little brother the SD-2, which in comparison, though neutral and well implemented, in direct A-B testing comes across as more piercing and sibilant, with vocals sounding a bit more harsh and shouty in their decay and the overall experience more akin to the brain knowing you are ‘observing a nice performance’ rather than the SD-4’s more believable, though more rolled-off signature. The immersiveness does come at the cost of forward mids I found, with the bass and highs spreading around you and putting you in the midst of the performance. So the V-shape is not a bad thing. It seems to me a great approach to what the designers intended, which from chatting to Marco of Inear via Gmail, was to render a balanced and highly immersive sonic experience. Goal achieved in my book.
What I want to talk more about is the ‘ambient fuzz’. Ok what does that even mean? Well, in looking at and feeling the  differences between the neutral SD-2 and the ‘natural’ SD-4 I equated it to how it feels to witness a good recording from slightly afar next to being at the gig itself. Feeling the reverb of the slightly distorting bass off the stage cabinets and knowing you are at a live music show. This is the SD-4. What I mean by that is the rolled off treble and extra bass of the SD-4 led to my brain’s extra belief that I am right in there with the artists and enjoying them just metres away like at a live gig. Hence my review title Putting the ‘Fun’ in Pro Audio’. But let’s do some song comparisons between the SD-2 and SD-4 to elaborate. If you click through on the youtube links and are the lucky owner of a stagediver iem (or two) then my words may make direct sense but for those others reading having yet to try an Inear Stagediver iem … well take it all as points of reference. 
Some Songs for Comparisons with SD-2
Low – Words
A lovely song I constantly use for trying out new phones. Lots of space to let me see how each instrument is presented. 
SD-2 – vivid cymbals yet the bass sounds quite dry and hard edged (but nice). The vocals are also nicely separated from the lows and highs. It’s all very spacious and coherent. I found the soundstage stopped just under my skull and had descent depth. The bass is certainly there but it is the mids that really pop with energy with the highs being relatively present too.
SD-4 – the bass line is more rounded and wet sounding, and potentially a touch boomy but it sounds great and more real. Cymbals are very different! They sound flatter like they are more rolled off yet somehow they hit with more impact than on the SD-2s. Vocals are also a little further back in the mix and ‘groove’ in the song more than ‘pop’ as with the SD-2s. The bass which is in general much improved over the SD-2s can at times blend more into the mids but again I found this totally fine. Even when it does the highs are totally unaffected. Lastly, though at first blush I thought the soundstage on the SD-4 may be narrower it is due to you being more at the centre of things. Which in my book is always the preference in an iem or headphone. 
Cliff Martinez - Solaris OST 2002 – Is that what everybody wants
SD-4 – I in fact have hardly any notes with the SD-4 as I drifted off with them in my ears. All in all they just connected me with the track and its dream like composition carried me off. Total win for how effortlessly engaging and natural the SD-4 are.
SD-2 – Compared to the SD-4 they are more distant but still very coherent sounding iems. They felt more analytical and less likely to send you into a murk of music induced dreamland. Perhaps they were a touch more spacious than the SD-4s yet I felt in this spaciousness I was observing the track more than emotionally participating in it as I was with the SD-4s.
Stars of the Lid – Requiem for Dying Mothers Part 2 & Down 3
Requiem for Dying Mothers Part 2 is a great track to test how an iem can generate a nice low sub-bass rumble. The SD-4 does this very well for a BA driver iem and is really engaging and enjoyable. It is the end of the next track Down 3 however, with the recording of a tram accelerating off its station that the SD-4 shows its true quality. Compared to the SD-2 the SD-4 renders the field recording in a magical way that makes the brain think not of , again, observing something cold and in a calculated way, but how the brain may remember a similar set of sounds watching a TV in childhood. The sounds on the SD-4 appear the way the brain thinks they should. It’s all very hard to describe but emotionally it is there and is very real. By being less neutral and more analogue the SD-4s achieve a means to make you feel included in what your ears are hearing. You are there!
Few last words
One thing I also really appreciated with the SD-4 was that if there was no obvious bass in a track it was almost like they became an SD-2.5 , and the mids and highs dominated effortlessly and very coherently despite the lack of the lower frequencies.
Also I had some spintfit tips on hand to try out with the SD-4 and I found they vastly improved the comfort from the standard tips. As they pivot they allowed for deeper insertion and as the jaw moves so do they and so all round comfort is massively improved. Not that the stock tips are bad at all but if you do struggle be safe in the knowledge that the spin fits fit the Stagedivers perfectly and besides comfort also noticeably improve transparency, and with a nice seal, bass also.
So all in all would I recommend the SD-4? If you understand and are happy with the type of sound balanced armature drivers produce and want an iem with a great immersive soundstage, lovely sense of a live performance and enjoy also the unique aesthetic Inear have brought to the shell design then yes , if you can afford it, please go ahead and grab one! I doubt you will regret it. 
Thanks again to Inear for loaning me the SD-4 for 2 weeks for this review. Happy Spring! 
nice read! they sound like they are a natural sounding iem  to listen to music the way the artist intended to. i like lots of detail but sometimes there is just to much taking away the musicality of the song. great review.
Thanks Guys. Check out the Sony XBA Z5. That is my fav iem of all time. Esp balanced. 
I love Inear's Product especially SD4 and the TOTL PP8, for my ears they are some of the most natural sounding in ears, and btw i've tried Z5 and prefer SD4 by miles... nice review by tne way cheers!!


New Head-Fier
Pros: best fit for universal iem, sound
Cons: a bit recessed mids
Review Inear Stagediver 4 “Perfect Fit Mk IV” (English Review)
Writer : Mikku
Inear StageDiver 4
Price : 10 Million (IDR)

Technical Data:
2-way-system (4 drivers)
Transmission range approx. 20 Hz–19000 Hz
Output sound pressure 120 dB
Impedance 22 ohms
Cable length 140 cm / (4'7.5")

I Love reviewing audio gears somehow… I just love it, but before you read my review I suggest you to take my review with a grain of salt since most likely I won’t use any freq graph and reviewing cans based on my ears only.
I bought this SD4 secondhand with an excellent condition, just lacking some accessories like the box, and some spare filter (I guess?). I still get the original pelican case and the original 4 size tips though. Actually I prefer this kind of packaging more than a grandiose one like some of iems that I’ve seen or owned, a supremely durable pelican case with cleaning tool and some eartips is just what I need for a perfect packaging.

This is what Inears stagediver are famous for, it’s unprecedented ergonomics!! (at least for my ears lol), when it comes to fitting actually Phonak could come really close with it’s perfect fit series, but it has a different sensation from what inear offers, while phonak is lightweight and feather-like in your ears but it still has downside, not all of its series has detachable cable, only 232 and it’s using a proprietary pin, also the cables could feels a little bit stiff sometimes, in the other hand inear fits like a glove in your ear I think this is what it feels like to use a ciem (haha I don’t have a ciem yet) and it has detachable cable using a normal 2 pin type, and the stock cable is twisted and feels so durable. So yes in terms of universal iem I believe that inear is still the best when it comes to ergonomics.
Now, the sound, the overall sound of SD4 is natural, smooth, and musical. Starting from its bass you’ll realize that it’s definitely a non-neutral bass, quite big (not a basshead level though), punchy, and deep, what I love  from the bass is the texture, it’s smooth and very well defined, try a Japanese song AZU – For You, wow! Lovely! Hits the sweet spot, not many cans could reproduce such a high quality smooth-textured bass, but in the same time, it might not suitable for rock music because of its smooth texture.
Go on to the mid, I know this review will be quite different from what others say about SD4, I’ve read some review said that the mid of SD4 is quite neutral, but what I found here is quite different, since my benchmark for neutrality is er4pt, I could swear that SD 4’s mid has a warm tilt to it. Like its bass, it has also a smooth-textured mid that makes a lovely  experience when you hear a vocal song, eemmm try an example Diana Krall – Frim fram sauce, now change to Ed Sheeran – Shape of You. Even though the genres are different but the vocal stays, it’s not forward, never too prominent, but very clear and well presented without any sibilance or any annoying peaks, I could feel that somehow it’s kinda laidback.
Go on with treble…. Nothing wrong here… I mean.. in a good way.. never gets too blunt nor too piercing, just there…. I couldn’t really describe this. But I could say this is an example of how treble done right, the timbre is also spot on and could extend really well up there.
If you’re a detail lover, I’m not sure that you’ll find what  you want here, SD4 is detailed without a doubt, but it doesn’t brag about it, but instead just sound musical and flowing until you notice that you could find some micro details that you don’t usually hear.
Soundstage is vast and has a quite grand 3D aspect (wide with height, front,and back dimension) but sadly quite lacking in depth.
If you love imaging for instruments, this could be an interesting choice for you, it could portrays every instruments in a great pinpoint imaging.
Vs Shure 846 : 846 has somehow darker yet more impactful and energetic sound, livelier vocals and more punchy deep bass, but lacks the soundstage and imaging also the sweet and smooth vocal that SD4 has. I think they’re in the same class, so it’s a matter of preference.
Vs Dita The Answer : Dita is definitely more energic with more punchy dynamic sub bass and more sparkling treble, but at the same time it’s definitely more harsh with some really bad peaks and not as refined as SD4. SD4 is more lush and laidback but surprisingly more detailed and has better texture from up to bottom.
Vs Fitear Parterre : Parterre has punchier and much bigger midbass, wider soundstage, darker treble (but sometimes better timbre[dunno how… fitear’s magic I think lol]), SD 4 has better extension both upper or lower register, narrower soundstage but more 3d imaging. I love em both so it was a hard choice for me to choose one of them to buy.. but in the end SD4 suits my music better, while parterre is better in classical music.
VS SD2 : SD4 is actually like SD2 but add extension from upper to lower register and pull the vocal backward a bit and add some upper mid sweetness on it, also add better soundstage and imaging, voila!! there you go
Vs SD3 : SD3 is darker and much boomier, SD4 is definitely brighter but smoother, with tighter yet deeper bass
In The End SD4 is without a doubt a high end product with a soothing smooth musical sound, but still detailed and very capable in terms of soundstage and imaging. One of its major selling points is the unprecedented ergonomics for universal iem.
Build : 9/10
Fit : 9.5/10
Isolation : 9/10
Bass : 9/10
Mid : 8/10
Treble : 9/10
Detail : 8/10
Soundstage : 8/10
Imaging : 9/10
Layering : 9/10
Value : 9/10
Rank: S


twister6 Reviews
Headphoneus Supremus
Pros: custom-like universal shell design, very comfortable fit, great isolation, bright revealing tonality with plenty of low end impact.
Cons: slippery shell, included eartips selection could be better, additional cost of earwax replacement filters.

Big thanks to InEar and Musicteck for providing a review sample in exchange for my honest opinion.
Manufacturer website:
Musicteck website (official InEar US distributor):, also available on Amazon.

When I received my review pair of InEar StageDiver SD4s monitors, I thought they made a mistake and instead of universal StageDiver series sent me a custom one from LivePro series.  I have reviewed multiple dozens of universal and custom IEMs, but never seen such a unique shell design which looks like something generated from a custom ear impression mold.  Later I learned that SD shell was created from an overlap of over 500 different ear scans used to come up with one common shape for universal fit.  I'm probably jumping ahead of myself with design impression and will definitely come back to it later in more details, but wanted to mention that StageDiver design got my attention from the first look!
While being familiar with so many different US and Asian IEM manufacturers, German InEar was never on my radar until I was asked by their official US distributor (Musicteck) if I’m interested to take their flagship StageDiver model for a test drive.  I was pleased to learn that InEar takes care of all the development and production, uses the latest CAD tools, and implements advanced 3D manufacturing system.  Also, they target different groups of audience with products designed for pro musicians, music enthusiast, broadcasting professionals, as well as making hearing protection and communication devices for those involved in outdoor construction and car racing.
The StageDiver SD4s model represents their flagship in-ear monitor quad BA driver design and will be the focus of my review.  Just for clarification, the “s” suffix of the model name stands for “smaller” shell version which they also offer in a regular size under SD4 model name, identical in spec and performance but slightly bigger in size.  Now, let’s take a closer look to find out about my experience with SD4s after spending 3 weeks of testing.
Unboxing and Accessories.
There was nothing special about the unboxing since the packaging itself consist only of Pelican 1010 micro case with a branded company sticker on top of the cover.  In theory, you are not going to get a better protection than these common Pelican micro cases, and visiting InEar website can provide you with all the spec details.  Sometime I still crave to see a fancy packaging box, though perhaps it’s just me reminiscing good old days of brick’n’mortar stores where I as able to visit a physical place and browse the isles while looking at the packaging to read about the product inside.  But I have to be realistic, and it looks like InEar followed a robust protection case packaging route with more emphasis on a product inside.
Opening the case reveals a pair of SD4s with a surprise of a “custom” universal shell, a set of silicone single flange eartip pairs in XS/S/M/L size, gold plated 1/4” adapter, and 3 cleaning wipes (!!!).  With an adapter, I usually consider it as fillers for IEMs since many people use earphones with portable sources, but I have a feeling it was included here intentionally since InEar puts an emphasis on professional use where musicians often deal with pro equipment and 6.35 jacks.  Eartips cover different sizes, but for me personally I found an absolutely necessity to use Comply tips (T500 size).  As much as I'm not a fan of fumbling with foam tips, I needed these badly to improve the seal in order to bring up the bass and to tame down upper frequencies.  This fine tuned the sound to my personal liking.
With cleaning wipes, I’m puzzled.  Perhaps the idea of universal shell suggests sharing and maintaining a proper hygiene, thus a necessity for wipes.  Not quite sure about this one, but it was definitely something different which I haven’t seen with any other IEM or CIEM during unboxing.  Overall, unboxing experience was very basic and the amount of accessories was limited by the space inside of Pelican protection case.  Lack of packaging box is not a showstopper, but I would suggest to include at least a pair of T500 Comply tips – they do come in handy!
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The original stock cable that comes with SD4s is a typical generic OFC wire in a tight rubbery jacket, very pliable, and with hardly any microphonics.  Though it's a generic cable, the 3.5mm gold plated 90deg plug stands out with a unique flat housing and a good strain relief.  It was refreshing to see something different, and it fits all my DAPs without a problem, but I wish the collar of the plug would have been a little taller to accommodate thicker smartphone cases.  It worked ok with mine, but left hardly any margin.  I know, cable is replaceable and some don't even care about using TOTL IEMs with a smartphone, but I found a brighter SD4s signature to pair up well with warmer sound of my Note 4.
From the headphone plug you have 3 twisted wires going to a rubbery y-splitter with a good strain relief at each end.  Having a dedicated y-splitter instead of a shrink-wrapped one always a plus, but here it also means combining ground wires going down to the plug.  Does it make any difference versus 4 twisted wires with separate grounds?  I didn't hear any sound changes while comparing to my other generic OFC cables with separate ground wires, but you never know if someone decides to re-terminate their cable with a balanced plug.  Going up you have a clear tube chin-slider with just enough friction not to slide freely, and further up you have memory wire underneath of a soft flexible tube, both attached to standard 2-pin connectors marked with Red (right) dot and Blue (left) dot for easy id.
With SD4s shells having recessed sockets, these connectors went right in without any problem, though you have to be careful since the socket is slightly angled and you have to be sure not to force it in.  But as I mentioned before, this is a universal 2pin connector which should be compatible with aftermarket cables.  The big question here, is there a benefit in upgrading SD4s cable?  I will talk about SD4s sound signature later in the review, but per my own personal preference and taking into consideration a brighter and more revealing signature of these monitors - I didn't like the effect of pure silver or pure copper or SPC cables which made sound crisper and brighter.  Stock OFC wires kept the sound smooth and non-fatigue.  Your mileage may vary, but in my opinion there is no need to invest in any replacement cables to enjoy SD4s to their full potential.
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I already mentioned in the intro of the review that a shape of SD4s was derived from overlapping of over 500 ear impressions to come up with one unique universal design.  I found they fit to be very comfortable and the shell, which appears to be made from acrylic material, to be lightweight and slick.  Actually, it was a bit too slick where you have to be careful when replacing the cable because the grip is rather slippery, and I would suggest doing it over a secure surface.  There is no issue otherwise when cables are attached and the only way to wear SD4s is with a wire over your ears.
Though the shells have a black glossy piano finish, InEar offers an optional wooden faceplate veneer for an additional fee.  I love the idea of IEM/CIEM customization, though in case of SD4s I'm not so sure any additional customization is even necessary, but it's always nice to have it as an option.  Also, you have a choice of going either with a standard size shell or a smaller compact shell.  For my review I choose a smaller shell and found the fit to be just perfect with an excellent isolation.
Even so they have universal fit, I still found myself putting them in my ears and taking them out with a typical clock-wise rotation, similar to how I handle CIEMs – just a force of habit.  Due to a unique shape, the shells are not symmetric and there are plenty of clues to distinguish Left from Right sides.  As I mentioned before, the recessed socket accepts 2pin connectors which have red/blue dots, the marking on the shell has company/model and a serial number with R/L suffix, and also the nozzle has a red/blue filters which is hard to miss.
The SD4s features removable/replaceable filters, not for a sound modification purpose but rather for keeping earwax away from the drivers.  Even so SD4s has its 4 drivers partitioned in two-way system with two low drivers and two mid-high drivers, they go up to a single bore opening inside of the nozzle where sound is mixed going into your ear canal.  And to protect earwax from getting inside of the nozzle, they have replaceable cerumen (earwax) filters which are sold in a set of 15 color-coded pairs at an additional cost of $29 (here).  The set comes with a really neat dispenser which also has old filters collector, and a special tool to remove and to replace these.  Personally, I get very little earwax build up so these can last me a very long time, but it could be a different story for others.  You do have to keep in mind the additional cost of buying replacement filters, but you do get 15 pairs which could last you awhile.  Also, in a typical German engineering fashion, I found the filter replacement steps to be quite engaging.  Furthermore, keep in mind that you can get TSX500 series Comply eartips which already have earwax filter built-in.
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Filter replacement.
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The fit.
Sound analysis.
I don’t preach about burn-in, but simply state that I believe in what I hear.  Even with multi-BA driver monitors there could be a burn-in effect of solder joints and miscellaneous crossover/filter components.  The reason I’m bringing this up, out of the box I really liked how SD4s paired up with Linum BaX cable and even suggested to Musicteck who carries cables in addition to earphones, to sell it as a bundle.  75 hours later after a burn in where I left SD4s playing alone, the BaX made sound too bright for my taste, and I went back to a stock OFC cable.  Now, with stock cable and TSX500 Comply tips while being driven from my “reference” Lotoo PAW Gold source, I was ready to analyze the sound.
I hear SD4s to have a slightly V-shaped sound signature with a bright revealing tonality.  These are designed for performing artist where you typically find CIEM shell for the best fit and isolation, yet SD4s is able to accommodate all that with their universal shell design.  Often with V-shaped signature you will find a sound tuning where the mids are scooped out too much, but in case of SD4Ss I hear it more like a boost in mid-bass region and also enhanced upper mids and treble.  Actually, treble is not just lifted up but also extended pretty far to reach some piercing airy highs.
In more details, sub-bass is present and quite extended, but the rumble quantity is at a moderate level, maybe closer to a neutral level.  The star of the low end is a tight punchy mid-bass with an overall articulate bass performance, always under control and never spilling into lower mids.  In some songs I felt like upper mids/treble overpowered low end a bit, but I was still able to distinguish a tight punchy bass that always cuts through the mix with a fast attack/speed.  With a supplied silicone tips, even the largest size pair, bass was lacking in quantity until I switched to Comply which improved the seal and brought up the low end performance.
Lower mids are on a thinner side, not much contribution to the body of the sound but rather contribution to v-shaped signature due to having a slightly recessed perception.  Contrary to that, upper mids are bright, very detailed, quite revealing, and with plenty of crunch.  When it comes to vocals the focus is not on natural organic full body performance, but rather accuracy and details.  Those who prefer lush warm natural vocals need to look elsewhere since SD4s is not about that, at least not to my ears.  As a result my perception of vocals was a bit on a grainy side which became slightly fatigue over an extended listening period while using silicone tips.  Again, I strongly recommend Comply (T500) eartips which do the magic of smoothing out a few harsh peaks.
Treble is bright and clear, nicely extended, full of crunch and airiness, and very crisp.  I'm not gonna lie, with the original silicone tips a few of the test tracks got close to a threshold of my sibilance tolerance, but Comply T500 set of eartips got everything under control.  Being so used to warmer and smoother sounds of headphones I have been reviewing lately, this was quite a revelation of details that jumped right in my face, and thanks to foam eartips I was actually able to enjoy a longer listening session.  As a disclaimer, take this with a grain of salt since we all have a different threshold for high frequency tolerance.
Soundstage expansion was impressive in all 3 directions.  While not exactly on a holographic level, the width/height/depth were all above the average without any exaggeration.  Here, I can also see the effect of treble extension with extra airiness which contributed greatly to separation and layering of instruments and vocals.  There is absolutely no congestion of sound and everything could be easily distinguished.  I also found imaging to have a good placement of instruments and vocals, very accurate position where I can pin-point everything.
Last, but not least, InEar specs SD4s at 26dB of isolation which I’m not equipped to measure exactly but can definitely confirm – outside noise was attenuated significantly.  Plus with Comply foam tips, were I actually prefer to use TSX500 that have a rounded comfortable shape, I felt the isolation to improve even further.   Furthermore, with a lip around the tip of the SD4s nozzle, Comply tips always stayed on secure when taking SD4s in/out of my ears.
SD4s vs CFA Andromeda – Both have a very similar soundstage where depth/height are nearly the same, while Andro is a little wider.  Andro sub-bass also a little higher in quantity and mid-bass has a slightly stronger impact, but the speed and the articulation of the low end is similar.  SD4s lower mids are thinner and overall mids are a little recessed in comparison to a more balanced Andro signature.  Also, SD4s upper mids/treble are more revealing and slightly brighter in comparison, but not as smooth or have the same natural body as Andro.  SD4s treble extends further and has a little more airiness.
SD4s vs UM Maestro – the height of soundstage is similar, but SD4s has more width and more depth in comparison.  Maestro has deeper sub-bass, while mid-bass is nearly identical with the same amount of punch and the same fast attack.  Both have thinner lower mids, but SD4s is slightly more recessed in comparison.  Upper mids in Maestro are a little smoother and have more body, making vocals sound more natural.  Treble is very similar, bright and crisp with plenty of airiness, though SD4s has a slight edge in extension.
SD4s vs 64 Audio U6 – soundstage has the same depth and height, but SD4s is a little wider in comparison.  U6 has a deeper sub-bass with more rumble, while mid-bass punch is nearly the same.  U6 lower mids are thicker in comparison, and have more body.  SD4s upper mids are more revealing and brighter, while U6 is smoother, warmer, and more organic in comparison.  SD4s treble has a better extension, brighter, more crisp and with more airiness.
SD4s vs Sirius – soundstage has a similar depth and height, but Sirius is wider in comparison.  Sirius sub-bass extends deeper and has more weight to it, while SD4s mid-bass has a faster punch and overall bass is tighter in comparison.  Sirius lower mids are more balanced, warmer, and with more body, and Sirius upper mids are warmer and smoother and more organic in comparison to SD4s which is more revealing and brighter.  SD4s treble extends further, more crisp and brighter, and has more airiness.
Pair up.
I suspect that due to its high 120dB sensitivity, there was some underlying hissing with most of the sources, but surprisingly it was mild and not too distracting.   And with 22 ohm impedance it paired up well with all of my sources.
I found neutral-bright tuned sources to enhance the revealing nature of SD4s, though it can also make them sound a bit too bright.  For example, it paired up great with LPG, Opus#1, X7 w/AM2, and N5 but could get a bit too bright with some of the tracks (based on my personal taste).
Contrary to that, going with warmer/neutral sources such as my Note 4, X3ii, and L5Pro made the sound more organic while still keeping it very revealing and detailed.  Surprisingly, it also paired up great with my laptop which is my warmest source.
By far, the best pair up was with Micro iDSD where switching to ECO gain and High Sensitivity sub-gain reduction yielded the sound quality which actually became more balanced and even added some body.  But the most important - the sound became more natural and organic.
On their website InEar mentions the company works according to a principle of "for Musicians by Musicians".  I don’t think I could have said it better myself.  Stage musicians need monitors that are comfortable to wear, have great isolation, and have a clear and detailed sound tuned for performance.  That’s exactly what you're getting with SD4s and their custom-like universal shell with a secure and comfortable over-ear wire fit, great sound isolation which can be enhanced with foam eartips, and a performance oriented sound tuned with a great low end impact and a clear detailed crisp highs.  For an extended listening session where you are craving a smooth relaxed natural sound, these might not fit the bill exactly, but music enthusiasts who want to squeeze out more revealing details from their in-ear monitors will greatly appreciate SD4s tuning and will enjoy the comfort of their fit.
Good work as usual man.  The SD4's are some of the bests looking universals out there I reckon.
Great review, my friend!
Nice review, SD2 is the best iem in their lineup. Most neutral. SD3 & SD4 seems to tuned more for stage use.