Below is an article I figure is written really good, and is worth sharing. With his permission, I am just going to paste this right here.
A very big THANKS to Audio Technica Singapore for lending me the whole 6 models of the relatively new Audio Technica Professional In-Ear Monitors, the IM series!
(FYI, I’m not working for Audio Technica, or their affiliate.)
I have around more than 2 weeks with these excellent sounding IEMs. Every day I try a model for the whole day. I used them during daily commute, in office, at home, and with different players, DACs, and amplifiers. Basically I'm quite impressed with the new IM series. With the right player / amp, none of them have any annoying frequency irregularities problem. I consider all of them, even with their own unique sound characteristic, more or less sound fairly neutral. Meaning, frequency responses are generally smooth. Some lean toward detail and clarity, some toward smooth and organic sound. Some emphasize on detail & clarity, some smooth & natural, and some are rather bass heavy. Still, their tonal balance can be considered fairly neutral. It’s simply awesome to have 6 IEMs with different variations of natural & rich sound signatures!
The Audio Technica IM series in this review:
ATH-IM01 : Single Balanced Armature driver IEM (47 ohms)
ATH-IM02 : Dual Balanced Armature driver IEM (36 ohms)
ATH-IM03 : Triple Balanced Armature driver IEM (34 ohms)
ATH-IM04 : Quad Balanced Armature driver IEM (14 ohms)
ATH-IM50 : Dual Symphonic 8.8 mm dynamic driver IEM (10 ohms)
ATH-IM70 : Dual Symphonic 8.8 mm dynamic driver IEM (10 ohms)
I received demo sets, without box and accessories, and came only with the medium size of silicon tips. The retail package will come with S, M, L silicon tips, and a pair of medium size Comply tips. The cable is detachable, 1.2 meters Y cable, with memory wire on the earphone ends. I find the new IM connector for connection to the earphone is very good. It clicks and locks the cable very well, and it seems durable. The connector shaped with polarity orientation, so no chance for cable to be plugged with reverse polarity.
I have no issue with comfort, I found they are all very comfortable on my ears after some adjustment of the memory wire. Good fit, and I could wear them for hours without getting fatigue. But we all have different size and shape of ears, so YMMV.
I found that the BA driver IEMs require proper pairing with the headphone amplifier / player for optimum sound, more than the dynamic drivers. The dynamic drivers IM50 & IM70 in general are easier to drive. Some of the BA IEMs affected quite significantly with the output impedance of the headphone amplifier (including player's build-in headphone amp). Some BA IEM get veiled and muddy with the increase of amp's output impedance, some get brighter in the treble, and some get their optimum performance at certain output impedance. That's might be one of the reason we sometime hear very different opinions of the same product. Different pairings different sound. Although there are many other factors that contribute to the sound quality, in this review I found that amp's output impedance is one factor that's worth to be observed. It will be elaborated more in this review.
The following players, DACs, & Amplifiers are the most used equipment in this review. Thanks to my friend Ong Wee Liang for lending me his Astell&Kern AK100!
The output impedance value is indicated in the bracket.
Violectric HPA-V200 (0.06 ohm)
Fiio E12DIY (0.19 ohm)
Yulong DA8 headphone output (0.26 ohm)
Audioquest Dragonfly v1.0c (0.40 ohm)
Fiio X3 (0.46 ohm)
iPod Classic 6th Gen 80GB (4.69 ohm)
Centrance DACport (9.78 ohm)
Astell&Kern AK100 (21.57 ohm)
Hifimediy UAE23 (203.26 ohm)
Except for Violectric HPA-V200, which output impedance value is taken from the Violectric website, the rest are results of my own measurement. I don't have lab grade instrument, only a simple digital Oscilloscope, Velleman PCSU200. So don't expect lab grade accuracy. The measurement results are only to be used as estimation of the amp's output impedance.
From here, I will use 'Out Z' for amplifier output impedance, to shorten it.
I noted on the following articles:
That Dragonfly indicated to have 12 ohms Out Z on the first article, and 0.65 ohms Out Z on the second article. Mine bought last Dec 2013 from Amazon ($ 99), version is v1.0c, after multiple measurement on my Dragonfly, the result consistently less than 0.5 ohm Out Z, 0.40 ohms to be exact.
Unfortunately my order for the Geek Out DAC has not been delivered during the review, so I cannot test Geek Out DAC with the IM series.
For the DACs, I used Foobar v1.3.1 on Windows 7 as the player, with WASAPI driver (WASAPI event).
ATH-IM01, ATH-IM02, & ATH-IM03, are natural sounding IEMs with very good clarity & transparency, leaning more toward the analytical sound signature, when compared with the rest. IM02 is the most analytical, but in a good way, and also the most realistic & spacious sounding, that with proper pairing, sounds way beyond its price point. I vote IM02 as the best value among the three.
IM01 & IM03 are less analytical than IM02. And though still have a very good level of detail; they are more forgiving to recording & amps pairing. I vote for IM03 for being the most musical sounding between the 3 models. IM03 has a very good balance of detail, transparency, and smoothness, while offering the most natural tonal balance.
ATH-IM04 offers natural tonal balance & good bass in a different way: smoother, warmer, and very intimate. It seems enough to have 3 models within the variety of clean & transparent sound signature, IM04 took a different approach. While still offering good and smooth frequency coverage from bass to treble, IM04 sounds much warmer, very intimate on vocal, but less detailed & spacious than IM02 & IM03. I think vocal is what IM04 is good at.
IM01, IM02, IM03, & IM04 generally have good & rich sounding bass, but the bass level is on the natural level, not the level for bass head.
ATH-IM50 & ATH-IM70 have excellent, big and powerful bass, with very beautiful vocal sound. Bass head & vocal lovers should try these models. Tonal balance is pretty close between the two, rather bass heavy but overall tonal balance still sounds natural and in good balance. They have pretty good clarity too, no muddy midrange like I use to hear with other bass heavy IEMs. Both have smooth & organic sound signature, with very good & realistic dynamic. Vocal is very beautiful on IM50 & IM70, full bodied, nice balance between warmness & smoothness, with good clarity and silky smooth treble that extends pretty high. Although clarity is good, IM50 & IM70 are not as airy & transparent as the IM02 & IM03, and they are not the analytical type.
FYI, I use the term ‘organic’ to describe the opposite of analytical sound.
In a very simplified analogy, IM50 = IM70 + subwoofer. Bass sounds bigger on IM50, also slightly more boomy. IM50 bass level is almost on my maximum tolerable bass that is still enjoyable. More than IM50 bass level, the tonal balance will be started to get out of balance, and the bass would be too dominant. IM70 bass is tighter, with better overall clarity. IMHO It is not about which one is better, both are excellent in its own way.
Other good news is, there are similarities of IM50 & IM70 sound signatures with their bigger brother, the famous full size headphones, ATH-M50! Meaning, those who like the sound signature of ATH-M50, most probably will love the sound signature of IM50 & IM70. It seems that Audio Technica has managed to pack most of the goodness of ATH-M50 in a much smaller package!
I predict IM50 and IM70 will be as famous as the ATH-M50. Well, let’s see
Kudos to Audio Technica for offering these giant killers in this price range!
Comparison with Ultimate Ears TripleFi 10
Let me try to compare the BA IEMs with the famous Ultimate Ears TripleFi 10.
Generally all the BA IEMs in the IM series have rather more natural tonal balance than TF10. TF10 IMHO is a bit colored, especially on the mids. TF10 sounds smooth and warm, but the mids sometime lacking of clarity for classical music, especially with high output impedance such as AK100. From experience, TF10 sounds best with low output impedance, such as with Dragonfly & Fiio X3. As for smoothness, warmness, detail, and transparency, TF10 is about in between IM03 and IM04. When all paired with matching amplifier, generally, IM03 is more detailed & transparent than TF10, and TF10 is more detailed & transparent than IM04. But also depends a lot on player and amplifier. With AK100 for example, TF10 sounds too warm for my taste. I prefer TF10 to be paired with Dragonfly.
Comfort wise, the IM series is more comfortable for me compared to TF10. The cable of the IM series is also more flexible and doesn't have the coiling memory effect like TF10 cable.
IM01 on AK100 sounds a tad more open than TF10, not much. TF10 has better frequency extension, better bass, and treble extension. But sometime for classical music IM01 may sounds rather more natural in tonal balance, and slightly better imaging.
IM02 has slightly more emphasized on the mids and treble, sounds more open & transparent (although sometime may sounds a bit harsh), TF10 sounds smoother and slightly warmer. Bass level and impact is about the same. IM02 is more revealing, TF10 sounds smoother and more forgiving. For vocal generally TF10 sounds better than IM02, smoother and warmer. But for good audiophile recording of acoustic instrumental and classical that sound best with more transparency and spaciousness, IM02 is better, sounds more open, transparent, with more focus and spacious imaging.
IM03 (on DACport) has better and fuller bass than TF10, and a more even frequency response from bass to treble, more homogeneous sound signature throughout the spectrum, while TF10 treble sometime sounds a bit on a different color and can be a bit detached from the mids. IM03 sounds more open and transparent than TF10. IM03 mids a bit more laid back in presentation than TF10 mids, but more open sounding. Overall IM03 sounds more natural than TF10, especially for classical music, where IM03 has better detail and transparency. Generally I prefer IM03 over TF10.
IM04 is slightly warmer than TF10, so for vocal TF10 is slightly more transparent than IM04.
Comparison with JVC HA-FXD80, Yamaha EPH-100, TDK IE800, & vSonic GR07 Bass Edition
For the dynamic drivers, let me simplified this comparison by listing what I like most to what I like less, top to bottom:
ATH-IM50, ATH-IM70, & JVC HA-FXD80
Yamaha EPH-100 & TDK IE800
vSonic GR07 Bass Edition
IM50 & IM70 sound signatures are different than the ‘Natural V-Shape’ sound signature of JVC HA-FXD80. All of them have excellent bass & dynamic. IM50 & IM70 IMHO are a better all-rounder, more natural tonal balance, and sound much better on vocal. I like the JVC HA-FXD80 better, for Classical, acoustic instrumental, and other recordings that sound best with airy & sparkling treble. JVC HA-FXD80 also slightly better on imaging, with wider imaging. But IM50 & IM70 imaging are also pretty good, and don’t sound congested. I like the three equally; they are good in their own ways.
Yamaha EPH-100 has closer sound signature to IM50 & IM70 than the others, but IM50 & IM70 have better bass and treble extension than EPH-100. While TDK IE800, another IEM with dual drivers that work in different fashion than the Dual Symphonic drivers of IM50 & IM70, doesn’t have the full sounding and tight bass of the IM50 & IM70. IE800 sounds clearer and more airy, and could be nicer for classical orchestra, but it doesn’t have dynamic as good as the IM50 & IM70.
vSonic GR07 Bass Edition sound signature maybe closer to TDK IE800 than others. But if I have to choose between the two, I prefer the TDK IE800 for smoother treble, and better overall tonal balance. But they are pretty close.
Recommendation on Recordings:
Audiophile & Classical recordings, recorded with natural tonal balance and natural stereo imaging as the goal, and best enjoyed with spacious sounding earphones, IMHO the BA IEMs: IM01, IM02, & IM03, are the better choice. They sound very natural, with excellent detail, transparency, spacious, focused & realistic imaging. For my classical collections & binaural recordings, IM02 & IM03 are my favorite.
Modern music that mostly recorded with closed miked approach, pop, vocal recording, and electronic music that best enjoyed with realistic level of bass, smooth, rather warm, & intimate midrange, the IM04, IM50, & IM70 are the better choice.
IM04 sounds quite different than IM50 & IM70, with flatter and more natural tonal balance. While IM70 has bigger bass than IM04, IM50 has even bigger bass. For house music, it is best with IM50 with its big and full sounding bass. As for my Stockfisch albums & other closed miked vocal recordings, they sound best with IM50 & IM70.
The sound signatures of IM50 & IM70 may seem to be more appropriate for modern genres. But they actually have good enough clarity and detail for classical music as well. After listening my favourite classical albums with IM50 & IM70, I found they are pretty enjoyable for classical as well.
Recommendation on Players and Headphone Amplifiers:
Although we can start with the general recommendation of the matching value of output impedance from the in-depth review, there are many more factors that contribute to the final sound signature, so personal audition is still the way to make the final judgement.
The BA IEMs are more affected with the value of output impedance. So if audition is not possible, it is better to choose the model that is more output impedance friendly, such as the IM03. For low power players and smartphones, that usually have medium to high output impedance, IM50 and IM70 are the safer models to choose. For example, on my smartphone, Samsung Galaxy S2, that I measured has around 50 ohms output impedance, it sounds best with IM50 & IM70. For those with better, dedicated music player, or good headphone amplifier, may consider the BA IEMs for more transparent and spacious sound.
For me, I like natural realistic type of sound signature. I like good clarity, transparency, rich treble sparkle, with spacious imaging, and not so much of a fan for warm sound signature.
Realistic level of bass is a must for me. Though I'm not a basshead, and I don't like oversized bloated boomy bass, but I want bass with proper level and strength, not anaemic bass.
From the 6 models, I really like the IM02 and IM03 clear & transparent sound signatures, while I also get addicted with IM50 and IM70 for their big, smooth & organic sound. Although I know IM04 will have its own fans, IM04 is not my cup of tea, too warm for my taste. In the end, I bought for myself the IM50, and my brother bought the IM03. IM50 is quite unique to my collection. I have mostly in my collection, clear and transparent, more analytical sounding earphones, so an earphone that sounds like having a build-in subwoofer, but still sound natural and clear, is something that I didn't have. And listening vocal recording through IM50 is highly addictive
Some Albums mostly used in this review:
ATH-IM01: The Purist. It’s not that I've tried so many single BA driver IEM before, but from memory, IM01 might be one of the best sounding single BA driver IEM I ever tried, and it competes well with other single BA driver IEM that cost more. It has natural and flat tonal balance, fairly rich & open sounding, with good level of detail.
Although IM01 doesn't have the low bass and upper treble extension of the higher models, it always sounds rich, musical and enjoyable. I don’t really feel IM01 is bass anemic, bass is quite sufficient. But IM01 bass will sounds anemic if compared to IM50 bass. Low bass extension is present, but not as powerful as IM02. And though not as transparent and airy as IM02, with AK100, I never felt IM01 is lacking in treble. Clarity and detail are good (especially on AK100). Not as revealing as IM02, IM01 is more forgiving with less than good recording. Dynamic is pretty good, but not as realistic as IM02. On AK100, Imaging is very good. Good depth and spaciousness. Imaging is even pretty close with IM03, when IM01 is paired with AK100. But IM01 doesn't perform that good on other players / amp, less open and spacious.
I had a chance to listen to Fitear 111 a few months ago, using my Fiio X3. It’s only a brief listening, no extensive testing on Fitear 111, and I couldn't do AB testing with IM01. From memory, I have a better impression with IM01.
IM01 is one of the best choices for long hours listening. Magically very good sounding with Astell&Kern AK100.
Output Impedance recommendation: Around 20 ohms.
For IM01, so far no other player sounds better than Astell&Kern AK100. It seems like IM01 is made for AK100 (20 ohm Out Z). Treble a bit too soft, and lack of transparency with very low Out Z amp. IM01 also doesn't pair well with DACport (10 ohms), sounds kind of hollow, lacking of bass and midrange body. Surprisingly quite ok with Fiio X3, but doesn't have the transparency, dynamic, spaciousness, and richness as when paired with AK100 (20 ohms).
IM01 on AK100 sounds better than IM02 on AK100. But on other players with low Out Z, IM02 is superior. For AK100 users, if IM03 is way out of your budget, IM01 should be on your list. It just sounds much better on AK100 than any other players I tried.
ATH-IM02: The Realist. One of the most detailed and revealing IEM I ever heard. The level of detail and transparency of IM02 is quite breath-taking, very realistic. When paired with a matching amp, IM02 sounds way beyond its price tag. Very open, transparent, and extremely detailed with spacious imaging. Instruments separation is very clear and focused, with clear space in between them. Tonal balance is natural with matching amp. Bass is on the level of natural bass, not for bass head, but bass sounds rich and detailed. Midrange & treble are also sound rich, with plenty of treble sparkle. IM02 is very revealing; it reveals recording quality really well. It is not friendly with 'not so good recording', but with excellent recording IM02 is very rewarding.
I vote IM02 as the best value earphone from the BA driver models. But not without warning, as IM02 is also the pickiest in pairing with the right amplifier. It is generally sounds best with very low output impedance amplifier (< 1 ohm).
IM02 has a unique characteristic, which the sound signature varies significantly by the increase of headphone amplifier output impedance. The higher the Out Z, the brighter the sound of IM02. I found this characteristic when tested IM02 with Hifimediy UAE23 (USB DAC). I and my friend were shocked when IM02 sounded so horribly bright and metallic on UAE23. After I did some observation, I suspected that output impedance is the culprit of the horrible metallic sound. So, I measured the output impedance of UAE23, and I got a second shock, to find out that UAE23 has >200 ohms of output impedance.
Then I tested IM02 with various players and amplifiers, with various output impedance (listed above), and the result is quite consistent. With all the low impedance players and amplifiers (< 1 ohm), IM02 sound signature is nicely balanced from bass to treble. The treble is very good, clear & transparent, natural and very balance with the mids and bass, no hint of excessive brightness with low Out Z amps. The treble is still at an acceptable level with 5 ohms output impedance of Mytek 192-DSD headphone output. It is started to sound rather bright with DACport (10 ohm). With AK100 it is definitely too bright for me. And this was quite surprising as I never knew AK100 for being a bright player. Comparing AK100 and Fiio X3 to check how much brighter IM02 on AK100, I had to increase the treble on Fiio X3 by 4 stops to match the brightness of IM02 on AK100. 4 stops increase of treble on Fiio X3 is quite a lot!
Output Impedance recommendation: As low as possible (below 1 ohm).
With high Out Z, Treble can be too bright and harsh. IM02 is not for AK100 with 20 ohm output impedance, treble is too bright. IM02 sounds pretty good and natural on iPod (5 ohms). Fiio X3, Dragonfly, Yulong DA8, and Violectric V200 all sound excellent with IM02. In the test, it sounds best with Dragonfly (v1.0c) & Yulong DA8 headphone output. IM02 is truly a good all-rounder when paired right.
ATH-IM03: The Musical. Natural, Smooth, open & transparent. A very musical sounding IEM. As open and transparent as IM02, and more friendly to players, amplifiers, & various recording quality. IM03 maybe has the most natural tonal balance in the IM series. Tonal balance is more natural than IM02. Smoother than IM02, IM03 is also the most musical sounding IEM in the BA series. Even though IM03 has very good detail, IM03 is not as revealing as IM02. But with IM03 music sound much easier on the ears. IM03 is a good all-rounder, from pop, vocal, jazz, to classical. But not for bass heavy material such as house music. Bass is about as good as IM02. Main difference with IM02 is on the midrange area. IM02 tonal balance has slight emphasize on midrange that makes midrange sounds fuller, where IM03 has a more natural level, flatter midrange. Midrange is more laid back on IM03 when compared with IM02, but not recessed, just on the right level, very balanced with the rest of the spectrum.
IM03 is a great transparent IEM. Maybe some might imagine that IM03 would sound bright, in fact it is quite natural, with nice silky and transparent treble that extends smoothly, especially with matching player / amp. IM03 may starts to sound rather bright with some players / amps that have Out Z lower than 1 ohm, but not always.
Another good news is, although Out Z still affecting the sound signature, IM03 doesn't change sound characteristic as much as IM02 with the change of amp Out Z. The increase of Out Z will smoother and soften the treble, but not drastically, and in a nice way (up to 20 ohm). IM03 sounds good with almost all the players and amps I have for testing, from low impedance amps to rather high Out Z, AK100.
For those who like smooth, warmer sound, may pair IM03 with AK100. On AK100, IM03 mids to upper mids is rather more dominant and forward sounding then the rest of the spectrum. Vocal is smoother, warmer, more forward and intimate. Less transparent, but sibilant free, while overall is still quite clear and natural. While for those who prefers more transparency & treble sparkle, may try IM03 with lower Out Z amps. On Fiio X3, Dragonfly & Violectric V200 treble sometime may sounds a bit peaky with mild sibilant on vocal. IM03 tends to be more analytical with low Out Z players. Some low impedance amp in the test that sounds very good with IM03 is Yulong DA8 headphone output & Hifiman HM-901. I had a brief chance to test IM03 on Hifiman HM-901 with Minibox Amplifier Module, around 0.56 ohms Out Z, which also sounds excellent on IM03. Sound a bit brighter than with DACport, but still very2 good. One of the best pairing for IM03 is with Centrance DACport (10 ohm), best synergy of clarity and smoothness. So either Centrance DACport or HM-901 would be my player of choice for IM03.
With DACport, IM03 can handle bright recording really well, something that really amazed me. How an open and transparent sounding IEM such as IM03 can handles bright recording quite well when paired with DACport. This is simply a good example of how a proper pairing is crucial.
IM03 is quite player friendly, and not difficult to drive. iPod Classic 6th Gen 80GB, with only around 30 mW per channel, and around 5 ohms Out Z, could drive IM03 nicely.
Output Impedance recommendation: 1-20 ohms.
IM03 is less affected to variation of Out Z, than IM02. For IM03 Lower Out Z increases the treble and transparency, and might cause rather thin sounding midrange and some mild sibilant on bright recording. IM03 sounds excellent on Centrance DACport with around 10 ohms Out Z, good mix of smoothness and transparency. But IM03 also sound excellent with some lower Out Z player / amp, such as Yulong DA8 headphone output, and Hifiman HM-901 with Minibox Amplifier Module.
ATH-IM04: The Romantic. The King of Pop, the most romantic sounding IEM in the group. IM04 is not about detail and transparency, but intimacy, warmness, & smoothness. Overall tonal balance is very natural, very good balance from bass to treble. Bass more or less the same as IM03, but IM04 is not as detailed and transparent as the lower models. For those looking for warm and intimate sounding BA IEM, IM04 is the one. Vocal is might be the strength of IM04. The warm and smooth sound signature of IM04 ensures fatigue free long hours music listening.
Some IEMs / Headphones best when played soft, some better when played loud. ATH IM04 is better when played loud. IM04 is the hardest to drive among other new IM series in this review. It requires higher voltage and power to sound best. IM04 sounds smoother and darker compared with IM01, IM02, and IM03. Although it doesn't sound muddy, IM04 is less transparent and less detailed compared with IM02 & IM03. Don't get me wrong, it doesn't mean that IM04 is lacking in detail, it's just because IM02 & IM03 have a very high level of detail and transparency. Less detailed is not always a bad thing, as with some bright recording and system, when the IM02 & IM03 started to sound rather harsh and fatiguing, IM04 is a better choice. IM04 is an IEM that can be used for hours without causing ears fatigue.
In my opinion, IM04 and IM03 are complementing each other for users with different sound preferences. Not like IM01 to IM03, where IM03 can be considered an upgrade to IM02, and IM02 an upgrade to IM01, IM03 and IM04 have different sound signature. Those who prefer clarity and transparency suits better with IM03, while those who prefer smoother and a bit darker sound signature might find IM04 a better choice. Vocal recording and modern Electronic music like Dubstep, might sounds better on IM04.
Tonal balance wise, IM04 sounds natural, slightly dark, and it has nice wide frequency coverage from low bass to upper treble, smooth with very good balance, without any emphasize on any frequency region, and no annoying frequency irregularity. I think Audio Technica has done a very good job to blend the color of sound of all the 4 drivers nicely. The sound signature of the 4 drivers blend really well, I didn't notice differences in the sound signature between the drivers, they match each other quite well.
Although the sound signature of the 4 drivers match really well, I started to hear some phase incoherence on IM04, that I didn't really notice on IM03 and IM02. Well, this is quite normal with multi-drivers BA IEM, and multi-ways speaker as well. The crossover circuit that splits the frequency spectrum to each driver will cause some phase distortion between the frequency regions. Crossover circuit is always one of the biggest challenges in designing multi-ways speaker. The more 'ways', usually the more obvious the phase incoherence distortion will be. The phase incoherence is resulting in less transparent sound, and less focus on instruments separation. But I would say the phase incoherence distortion in IM04 is mild, in fact, it creates a smoother and warmer sound signature that complements the other models in the IM series.
I prefer to pair the sweet, smooth, and warm IM04 with DAC+Amp that has good dynamic and transparency. On my setup, Dragonfly (v1.0c, 0.4 ohm output impedance) pairs quite well with IM04, sounds more transparent than DACport (10 ohm output impedance). Generally it is better to avoid pairing multi-drivers BA IEM with high output impedance amp, as the tonal balance might vary significantly. But of course that is not always the case, there are some multi-ways BA IEMs that quite friendly with Out Z variation as well. Playing the IM04 using my smart phone (Samsung Galaxy S2, with 50 ohms Out Z) really doesn't do justice, as general smart phones don't have the capability to drive IM04 to the optimum level. Generally IM04 is not as easy to drive as IM03. High end player / amp with very low Out Z is recommended.
IM04 is not so suitable with classical, and has better chemistry with closed miked recordings of modern genres. Listening Stockfisch recordings on IM04 through Yulong DA8 headphone output is simply a sheer enjoyment.
Output Impedance recommendation: As low as possible (below 1 ohm).
IM04 has better detail and openness with low Out Z amp. The increase of Out Z increases the warmness, and reduce the detail and openness. For example, it sounds very warm on AK100, yet still quite enjoyable, and with pretty good bass. Personally I prefer to pair IM04 with low impedance player / amp, such as the Dragonfly, Yulong DA8, and Violectric V200. In my opinion, IM04 sounds best with Yulong DA8 headphone output.
ATH-IM50 & ATH-IM70:
There are more similarities than differences between the two. As mentioned in the summary, the simplest way to describe the differences between IM50 and IM70 is, IM50 is like IM70 with an additional subwoofer. The bass difference is not too much, but well perceived.
Both have natural tonal balance with emphasize on bass. Bass is big and quite realistic on both, IM50 has bigger bas, and IM70 has tighter bass. On the midrange, IM50 vocal sounds fuller, and IM70 vocal slightly leaner but clearer.
I often recommend ATH-M50, the famous full size headphone from Audio Technica to my friends, and most of them very happy with the sound. Sometime they ask me if there is any earphone that has sound signature close to ATH-M50, for smaller setup & daily commute. Before I knew IM50 and IM70, my answer would be simply: “not really”. But now I’m happy that I can say: “Yes, there is!”
It is amazing that Audio Technica could pack most of the goodness of the bigger M50, the famous ‘M50 house sound’ into smaller packages of IM50 and IM70. Listening to IM50, IM70, and the full size M50, although they are not totally sound the same, but I imagine they seem to have been designed & tuned by the same company / engineer. They have the same house sound, organic, full sounding bass and midrange, good clarity, & smooth treble. Excellent on vocal, and a good all-rounder.
Comparing the 3, IM70 sound signature is closer to M50 than the IM50. Again, not about which one is better. Their sound quality, in my opinion, are about in the same category. M50 slightly has better clarity, and IM50 has slightly fuller bass. For vocal, I tend to like IM50 more. But it is all depending on the combination of player and recording. I simply like all of them, and could happily live with any of them.
The dynamic dual symphonic-driver is amplifier friendly, and not really affected by high Out Z. So I think it is not necessary to give recommendation of amp output impedance for IM50 and IM70. They sound good on all the players, DACs, and amplifiers I used in the test. Also sound good with smart phones, although not as good as the dedicated players and DACs. Generally I set the volume lower when listening to IM50 and IM70, they are quite efficient.
Even though IM50 and IM70 have a lot of similarities, I will try to describe in more detail the difference between the two.
ATH-IM50: The Gentle Giant. IM50 sounds BIG. It has the biggest most awesome bass in the IM series. Bass level is almost on the max of my tolerance level of good bass. Definitely a must try for bass head. Electronic and House music sound absolutely awesome on IM50, big and full of bass presence. But for IM50, big bass is not necessarily in the expense of clarity as what I often experience with other IEMs tuned for big bass. IM50 surprisingly still has pretty good clarity! Beside big bass, mids are smooth, full sounding with pretty good clarity, so vocal is full & sweet, not muddy. Treble is smooth and extended. Imaging although not as spacious as the BA drivers, but not congested either. Instruments separation is quite clear and focused. In the test almost all players and amps sounds good with IM50. Blessed with the goodness of the ATH-M50 house sound, IM50 handles bright pop recording extremely well.
The IM50 I bought, out of the box, sounds fairly identical with the demo unit that I guess already used for many hours. So burn-in is not necessary for IM50 to sounds good.
ATH-IM70: The Gentleman. IM70 sounds like a refined model of IM50. Bass is tighter, less boomy, with better overall clarity & transparency. If IM50 is excellent for bass head and house music, IM70 might be a better all-rounder that also equipped with tight and good quality bass.
At last, thanks for reading the rather long review!
And once again kudos to Audio Technica for the new IM series!
The New ATH-IM Series Cable
I really like the new IM series detachable cable. No fancy looking, simply good design and good quality cable. 1.2 meter Y cable, with L shaper 3.5 mm stereo mini jack. The cable is quite flexible and doesn’t have the annoying coiling memory effect.
The cable equipped with memory wire on the earphone ends. Personally I prefer without memory wire. Memory wire needs proper adjustment to become comfortable. I find it more practical and comfortable to wear over the ears without the memory wire (other IEMs).
Left and Right channel are on separated cable. This is good, no shared ground wire that causes high level of crosstalk (see my post of Crosstalk on Audio Technica M50)
Separated left and right cable also mean that the cable can be terminated for balance connection, to be used with balanced amp.
The detachable cable comes with new connector. The connector is properly coloured for left and right marking, and also shaped for proper polarity orientation. Not like the UE TripleFi 10 connector that can be plugged with reversed polarity, it is not possible to plug the IM connector with reverse polarity. Another good design from the connector is the locking ‘click’. It clicks really well, sometime a bit hard to detach the cable. This is to ensure good and secure connection; the connector will not become loose to quickly after frequent plugging and unplugging cycles.
The distance between the 2 pins is exactly the same as UE TripleFi 10 connector.
I hope there will be more variety of cable for the IM series, by Audio Technica or other third party cable. And I hope there will be the balanced version as well
More on Amplifier Output Impedance
I recommend this excellent article to learn more about amplifier output impedance:
Let’s take the extreme case with ATH-IM02. As mentioned before, when comparing IM02 on AK100 & X3, IM02 sounds much brighter on AK100 than on X3. The treble level of IM02 on AK100 is about equal to X3 with 4 stops treble boost.
I tried to lower down the AK100 high Out Z, using low Out Z amplifier. For this test I used Fiio E12DIY (0.19 ohms). With amplifier, the IM02 treble level back to normal. In this case, the amplifier acts as impedance converter. That’s one good reason, why sometime we need a headphone amplifier, not only for the power, but in many cases as an impedance converter, to have better pairing with the earphone.
I also tried the other way around, to increase the X3 Out Z, to simulate the treble rise on high Out Z player. I made a stereo mini jack extension with 22 ohms resistor terminated inside the mini jack connector to simulate 22 ohms output impedance. I plugged the mini jack extension on Fiio X3, and IM02 on the extension. And the result is quite consistent; I heard the treble rise up when I use the 22 ohms extension. Although the sound is not quite the same as with the AK100, but the 22 ohms resistor in the extension does increase the treble of IM02.
This is a good lesson for me, to put more attention in matching and pairing, especially for BA and multi ways driver IEM, and not to judge an earphone by using only one player.
original site link: head-fi earfonia