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Review: Westone AC2 dual driver custom in ear monitor

post #1 of 32
Thread Starter 






It seems fairly clear that the market for custom molded in ear monitors has really taken off over the last few years. I was just reading an old thread from 2007 where somebody was discussing their options for getting into customs: At the time the available models were in the $700 to $900 range and relatively few HeadFiers used customs. Fast forward a few years and we now have a wider variety of choices ranging from under $200 to over $1300, and a much larger user base as well.


Part of this trend can be attributed to the multitude of small companies that have popped up offering customs at lower prices than we had traditionally seen. Companies like FreQ and LiveWires offered good sound at a fraction of the normal price. At the moment we have 1964 Ears, Kozee Sound, and several others offering great entry level customs at very reasonable prices.


To attempt to capitalize on this somewhat new lower segment, well known IEM companies like Ultimate Ears and JH Audio released their own entry level customs. Both firms offer a dual driver model for $399 and both have been well received. Conspicuously missing though was one of the oldest and most well known players in the custom market, a company called Westone. Their cheapest custom model had been the single driver ES1 ($375), but from what I can find hardly anyone used that model, choosing instead to jump to the well regarded ES2 ($650). Perhaps Westone hopes to capture more of the blossoming entry level market segment with the release of their new AC series, which consists of the single driver AC1 and dual driver AC2. The subject of this review is the AC2.


The AC2 can be seen as a direct competitor to the JH Audio JH5 pro and the Ultimate Ears UE4 pro. All three are dual driver models and all three are priced at $399. Like the UE4, the AC2 is only available in clear. I assume that was a cost saving decision made by both companies, in order to devote a larger portion of the cost to things that affect the sound.


Despite being around for several months, and a decent amount of interest on HeadFi, I was unable to find an owner who could give me impressions of the AC2. They seem to have flown somewhat under the radar, possibly being overshadowed by another new release from the same company, the Westone 4 universal IEM. I hope I can shed some light on the AC2 as I feel it has a lot to offer and is somewhat unique in its price class.  


For those unfamiliar with Westone, they are one of the oldest and most well established brands in the custom IEM game, and have been around in the hearing aid industry for even longer. If you’ve ever gone to an audiologist’s office, chances are they were an authorized Westone dealer. I’ve gone to several different audiologists to have impressions done for customs and each time I’ve walked out with my impressions in a little box with Westone logos on it. Despite being an old and well established company, they remind me of a small startup when it comes to interacting with customers. I mean that in a good way. All of my emails were answered promptly, and my customs took just 10 days to be built.






The AC2 is a dual driver custom molded in ear monitor. As I mentioned, it is only available in clear. To keep it from being boring Westone puts their name in a rather nice font across the faceplate of each side for no extra charge. I never asked but I suspect this is a non-negotiable option. The shell is full acrylic (which means no heat sensitive tips like the ES series customs) and uses something called a “cold pour” technique which I’ll discuss later.


I can see inside to the drivers but I can’t identify them based on the numbers. This makes sense because Westone is large enough not to have to use off the shelf drivers, so these are probably built and numbered just for them by one of the large balanced armature makers like Knowles Acoustic. I see one fairly large driver and another smaller unit stacked on top piggyback style. The crossover seems to be attached to the larger driver, rather than floating at another location in the shell as is more common. Unlike any other Westone customs I’ve seen, the AC2 has a single sound bore; both drivers fire into a single tube which carries the sound down the tip and exits from a single hole. The merits of multiple sound bores have been debated on HeadFi with no clear conclusion, but I’ll default to Westone’s expertise in the matter. By their very nature, most or all universal IEMs have a single sound bore, so it can’t be too detrimental.


Here are the specs for the AC2:


Sensitivity: 119 dB SPL/mW
Frequency response: 20 Hz - 18 kHz
Impedance: 27 ohm



I notice they appear identical to the more expensive Westone ES2 custom. Wondering if this was just an ES2 in a different shell, I sent Westone an email with a few questions. They were very helpful in getting the questions answered, and actually forwarded my questions to their lead designer/engineer for more specifics. I’m going to paraphrase his answers because I never asked for permission to quote him and I don’t feel like bothering him with another email. The question he is answering was regarding the differences or similarities between the UM and W series models, as well as the ES line:



The Westone AC2 is designed for use on stage, and the sound signature is more like the UM2 except in a custom fit shell. 

The critical considerations for on-stage use in his opinion are the ability to clearly hear timing cues, high-hat cymbals etc., and that the earpiece is able to help convey some of the energy, particularly low frequency energy that is felt on stage. The AC and UM series products are designed more as a tool that the artist or engineer can use to extract the kind of sound signature needed to perform their best. When playing live the artist is using the monitor as a tool just like his/her guitar: it is something that helps make the music happen. 

The listening requirements for on-stage monitoring and the requirements for enjoying recorded-mastered music are in some ways very similar but in others quite different. The W series of products tries to reproduce what the artist and producer of a recording intended so that the listener can hopefully hear the final result of the artist, engineer and producer's collaboration. 


The Westone 2 is more of a cousin than a sibling to the AC2/UM2, in that they never intended it along with all "W" series product to be used as an on-stage tool. It was and is designed to do one thing - be the best "small" dual driver earpiece in the market.


The ES products kind of blur the line a bit in that they give the user of a custom-fit monitor the best fidelity, flexibility, and fit that they possibly can.


When asked specifically if the AC2 is just an ES2 with a less complex shell, he answered:


No, they actually will have a different sound signature. The AC2 is closer to the UM2 than it is to the ES2. Given a sound signature difference, the AC series products don't cut any corners with regards to components such as drivers, cable, etc.  They use the same pieces as the ES series products.


Obviously there could be different interpretations of how to accomplish the goals he discussed. And now that I think about it I notice the UM2 and ES2 share the exact same specs with the AC2. My guess here is that they all share the same drivers, but with slight tweaking for each model to produce the desired sound signature and to compensate for the differences in shell or housing. Interestingly enough, the W2 has totally different numbers, so therefore is more significantly different than the other three models.














Westone is generally known for good build quality and the AC2 doesn’t disappoint. I don’t see any bubbles or oddities inside the shell and it is generally clear and transparent. The Westone graphics on the sides are nicely done as well, adding a touch of uniqueness to an otherwise nondescript IEM. I only spot two areas that keep them from achieving perfection. First, there is somewhat of a distinct seam between the shell and the faceplate. Not a big deal, but it is worth mentioning. Secondly, there seems to be a tiny imperfection on the top area of each monitor. It is hard to explain, and was very difficult to capture in a picture, but since both sides have the same thing I’m guessing it has to have something to do with the cold pour construction process. It is a very minor thing and on a darker color shell it would probably not even be visible.


Speaking of the cold pour process: I’m no audiologist, and I admit that I don’t quite understand all the details about this process. Westone tells me that the AC2 uses a full cold pour acrylic body, which should be more durable than the UV light cure process that many competitors use. From an end-user point of view, all I can say is that the AC2 is probably one of the best fitting full acrylic customs I’ve experienced. I also notice that they seem to have a little more weight to them as compared to other dual driver customs. Not enough to be heavy by any means though. Possibly related to that is the fact that they make a somewhat different noise when the knock together or when you set them on a hard surface. Not that I go around banging my customs around… but when they do come in contact, the sound produced is more substantial, like tiny billiard balls knocking together. I can’t say if this is really an indication of quality though.


I asked that my AC2 be made to fit as deep and snug as possible, and Westone said they would do their best to accomplish that for me. Obviously that requires nice deep impressions to be taken. Mine must have been good enough because the fit on these is nice and tight and yet still very comfortable. As I tried to capture in the pictures, they are only slightly deeper than average, but more importantly the tip of the canal seems more full. I get very good isolation when I wear them, and I have to really try hard if I want to break the seal. Obviously every time they make a custom there are variables at play and this is just a single sample… but I’m very pleased with the results and have no need for a refit or adjustment.















It's hard to make it out, but the above 2 pics attempt to show the minor imperfection I spoke of.






As I mentioned above, my AC2 arrived in just 10 days time from when they received my impressions. Inside the well packed shipping box I found a retail style box similar to other Westone products I’ve seen.


Opening that box leads to the good stuff: a small zippered crush-proof case, a cleaning cloth, the usual wax loop/cleaning tool, a small amount of Oto-ease, and of course the monitors. The only option with the AC2 is a clear cable, which I absolutely love the appearance of. Unfortunately I’m less enamored with the unavoidable oxidized green look. See the posted pictures if you aren’t familiar with this phenomenon. The good news is that it is purely cosmetic, is not Westone’s fault (all clear cables do this eventually), and of course a different cable can easily be obtained if the green bothers you when it shows up.


In lieu of a hard copy user manual, Westone has included a “user information disc”. Pop it in your computer and you have access to all kinds of helpful info about the use and care of your monitors. Nothing on the disc is revolutionary, but it is well done, and once again reminds you that you are dealing with an established company who doesn’t cut corners.
















This is the gear that I used during my evaluation of the AC2:


Source: Lexicon RT-20 universal disc player, dedicated music server fronted by a Squeezebox Touch


DAC: Anedio D1, Yulong D100, Matrix Cube, Gigaworks DAC


Amps: Violectric V200, Matrix M-Stage, Yulong A100,


Portable: various combinations of Sansa Clip+, Sansa Fuze, QLS QA-350, and sometimes with the TCG T-Box or Vivid Technologies V1 as amps


In addition to the stock cable, I sometimes used a Beat Audio Supreme Rose cable for portable use, and a Beat Audio Cronus cable for home use. Just so nobody can say the stock cable was a limitation.













These are just the impressions of one guy. I do these reviews for fun, not profit, and I don't claim to be any special authority. Many people have agreed with my assessments of other gear but some have also disagreed, and I totally respect that. We all hear differently on a physical level and we all have different preferences as well, so I think it is almost impossible for one person’s impressions to apply to every other person. As with all my reviews, I hope you enjoy reading them and I hope they help our hobby to some extent, but I don't pretend that they are anything more than my opinion.





My first impression of the AC2 was that it did not sound anything like I had expected. Having owned and loved the ES3X for a while, I guess I was expecting a sort of “ES3X junior” type of sound. But what I heard was far closer to the Westone 3 – a spotlight on large bass, and slightly aggressive highs which can be good or bad depending on the recording. I haven’t heard the UM2 in a long time but I do seem to remember a similar flavor from that, so the comments made by the engineer at Westone certainly started making sense at that point. So while on the one hand the AC2 was different from my expectations, it still managed to maintain the Westone house sound that we’ve heard in other models.


The dominant aspect of the sound signature is clearly the bass. I really enjoyed it. It had excellent impact, great tonality, and mostly steered clear of the midbass hump that sometimes kept me from enjoying the W3 as much as I wanted to. I might even go so far as to call these “basshead” customs, or as close as I’ve heard to that description in the entry level price range.


When I say the word “basshead” combined with the term “entry level”, there are all sorts of negative examples that come to mind. Let me be very clear that the AC2 sounds nothing like the typical overhyped low end bass cannon that you might be thinking of. The Sennheiser CX300 is one example. What the AC2 does deliver is a rich, textured low frequency performance that approaches some of the best I’ve heard from an in ear monitor. As a drummer I know how difficult it can be to properly capture the weight and impact of a bass drum, especially when you don’t have a big dynamic driver moving a bunch of air. But the AC2 pulls it off very convincingly. It is fast, clean, punchy, and authoritative. It isn’t limited to bass drums either. Cello and double bass really shine as well, with plenty of warmth and realism to make the performance convincing. I loved listening to Julian Lloyd Webber, Yo-Yo Ma, and Mstislav Rostropovich with the AC2.


They also sound great with other less “audiophile” type music. The album “Light” by Matisyahu contains a fairly diverse collection of styles, some of which are better done than others from a sound quality standpoint. The AC2 allows this to shine through: we hear the almost subterranean bass line on “One Day” which I still wish had been recorded or mixed with more definition. We hear the punchy, almost dry sounding bass strikes on “We Will Walk”. We hear the general mushiness on “Smash Lies”, which unfortunately is just the way the song was made. The AC2 presents each track with an emphasis on the bass, but it never tries to cover up flaws or make things sound better than they should. But within the limits of the recording, the raw power and articulation are very addictive. The AC2 doesn’t quite manage to completely eliminate the midbass hump as heard in the W3, but it is diminished to the point of being far less significant. I am not bothered by this minor remaining hump and don’t find that it muddies the sound much, but I know some people are extremely sensitive to this sort of thing so it is worth mentioning. This minor issue combined with the huge presence and impact of the bass in general means that the AC2 is probably not the best choice for someone looking for an Etymotic ER4 or Fischer DBA-02 type of sound in a custom IEM.


Mids on the AC2 were initially hard for me to get a handle on. At times they seemed a little recessed, although I now realize that they are fairly neutral, and I had just been used to the slightly forward sound coming from my other customs. For that reason the AC2 required more adjustment when switching from another headphone. Eventually I decided to use it exclusively for a while, and that really helped. In any case, I’d call the mids on the AC2 somewhat relaxed and dry, although I don’t necessarily mean that in a bad way. They are very straightforward and natural, and certainly do not add any extra sweetness or wetness to the sound. At first this came across as a little boring but it grew on me and I now rather like it. It really seems to work within the context of the overall sound signature, and I’m not sure I’d want it any other way.


Although you won’t find any added emphasis in the mids like you would with something like an Audio Technica woody, it still sounds very good to my ears. Listening to Livingston Taylor’s album Ink, the AC2 allows his dulcet voice to shine through without being too sugary. I do miss a little of the immediacy present on his rendition of “Isn’t She Lovely”, which is apparent when using a higher end custom. But the AC2 manages to capture his smooth laid back vocals on “Baker Street” in a very convincing way. The neutral even tone of the mids actually highlights something that I’ve read Livingston write about with regards to music: He likes to say that a performance is not something you give, or that an audience takes away with them; it’s a conversation that relies on both the performer and the audience being prepared for whatever happens next. Obviously he has a live performance in mind, but the idea still translates somewhat to the recorded medium. The uncolored mids of the AC2 allow flexibility to adjust to whatever the recording requires. With that said, the rest of the sound signature is not as neutral, so you still get a certain AC2 flavor no matter what.


So far what we have are the makings of an absolutely amazing monitor that has a lot to offer compared to the competition, assuming of course that it fits your preferred style. Unfortunately the highs are not quite up to the same level, and will be a bit of an issue for some listeners. I find the most difficult of explaining the AC2 is properly conveying the sound and feel of the highs, but I’ll do my best. This section will be longer because there is more to describe.


For anyone who has experienced the presentation of the W3, the AC2 offers similar performance in the highs. There’s just no getting around the fact that both models add a certain amount of sibilance to vocals. I think some W3 users had their problem accentuated through a less than perfect seal, and the custom fit of the AC2 obviously alleviates that aspect. So the sibilance issue may be less for some users who never actually experienced the W3 at its best, but it is not completely eliminated. I find it to apply equally to male and female voices, and in general it appears more often in poor quality recordings than really good ones. But you just never know what you are going to get: The new album Paper Airplane by Alison Krauss & Union Station is a good example of this. The title track features vocals by Krauss and is undeniably sibilant through the AC2. Switching to the Unique Melody Merlin and the JH-13 as references, I can clearly tell that this harshness is not on the recording and it is the AC2 adding it to the vocals. Aside from that aspect the rest of the track sounds perfectly fine and meets the standards set by the competition in this price range. Moving on to the next song, Dust Bowl Children, we get Dan Tyminski’s unique vocals that sound as clear as day with no harshness or sibilance whatsoever. Skip ahead again to Lie Awake, and we get Krauss sounding much better than she did prior. There is still just a hint of extra crispness when she says an S or T sound but it is very much toned down compared to her prior track and should prove very listenable for most people. The problem in my mind is that you never know when you’ll encounter a song like my first example, which for some listeners would prompt them to skip to the next track.


The other area where I didn’t care for the highs was when listening to a subgenre of rock called “screamo”. I admit I don’t care for that name but apparently it is widely accepted so I’m using it here. Somewhat well known bands in this genre include Thursday and Thrice, both of which I occasionally listen to. Lesser known acts that I enjoy include Underoath and Dead Poetic (more specifically their album New Medicines as they have since changed their sound a bit). None of them sound terrible through the AC2 but the sibilance tends to put a damper on an otherwise very enjoyable presentation. The already harsh vocals and distorted guitar can sometimes be hard to bear at higher volumes even when using squeaky clean headphones, and any added sibilance from the AC2 can push them over the edge. Once again though we find this varying from song to song, so it’s not like you have to avoid that style of music altogether. But awareness that it is not a strong point is definitely required.


Lastly, I have to say that cymbals do not sound great on the AC2. It’s interesting because hi-hats sound very nice, and even when played somewhat open they retain their clarity. But crash cymbals end up sounding pretty similar to an open high hat strike, which is not the way they should sound. I listened to some random drum recordings that I have, and had a hard time telling the difference between different models of splash cymbals, crash cymbals, ride cymbals…. They all ended up sounding a bit homogenized. Once again good recordings fared much better than poor recordings and the more refined styles outperformed the aggressive. So Hiromi mostly sounded acceptable, but Pearl Jam could be a little rough on some tracks.


So with that being said, is there anything to like about the highs? There sure is! Detail retrieval was very good. Stringed instruments (Alison Krauss & Union Station again) were especially crisp and clear. And I absolutely loved the way they handled electronic music in general. I’ve had a resurgence of interest lately in so called “ambient” type music like Nalepa and Electronic Noise Controller, and the AC2 is one of my favorite headphones for that type of music, regardless of price. This leads me to my next point of discussion, which is soundstage.


The AC2 has excellent soundstaging. Not just for a dual driver custom, not just for a relatively cheap custom, but just excellent period. It’s a little different than others I’ve heard though. Others like the Unique Melody Merlin are extremely expansive but still maintain a fairly up front and intimate presentation. The AC2 is not really like that. In this case it seems the spacious presentation is a result of the mids being pushed back a bit in the mix. Combined with the robust bass, you get the impression that you are sitting rather far back in the performance space, maybe even back row. This was a bit off-putting at first, but after getting used to it I started really enjoying it. It’s just a different take than other customs that I’ve heard. If you tend to focus on the vocals in every song you might have a bit of a hard time here, but for most people I think it will be pleasing. I actually think they sound more like full size headphones than most in ear monitors do. That isn’t a judgment one way or the other, it’s just an observation. When I use IEMs exclusively for a while and then switch to big headphones, I almost always feel like they sound too detached and distant for the first 10 minutes or so. My ears need to adjust to the physical space between them and the drivers. The AC2 sort of replicates that feeling.






Unfortunately my Westone UM3X and W3 are both out on long term loans to friends who don’t live near me. So I was not able to do direct head to head comparisons with the AC2. But from memory, I’d say that the AC2 is a bit of a mix of those models. It starts with the basic W3 signature, but has the better bass control and especially midbass control of the UM3X. Bass quantity still approaches W3 levels though. For that reason, bass quality is superior to both of them in my opinion. I had the UM2 at one point but it’s been so long that I can’t make any conclusive statements about that. Soundstage is easily on par with the W3 (which I found to be very good), if not a bit better. High frequency extension might be a little shy of the W3, likely attributable to the smaller driver count. Overall though I think a user who moved from a W3 to the AC2 would be pleased with the result.


The Ultimate Ears UE4pro is direct competition for the AC2. They have very different sound signatures, but I ended up preferring the AC2 about 80% of the time. In comparison, the UE4 bass does not sound as realistic. This is not just a volume issue either. It doesn’t seem to capture the real, tactile feel that the AC2 can produce, and it tends to break up when asked to do too much. Mids on the UE4 are much more forward and aggressive, which is sometimes preferable and sometimes not. The only clear advantage had by the UE product is in treble clarity. While this is helpful with certain music, I often found myself thinking the UE4 was boring in comparison and ended up being willing to put up with some sibilance in exchange for some emotion. The AC2 sounded more three dimensional with more space between instruments and especially more depth to the whole presentation, making the UE4 seem a little flat in comparison.


The 1964-T from 1964 Ears is a triple driver model with dual low frequency drivers and a single driver for highs. Comparing it to the dual driver AC2 you would swear that it was the other way around. The AC2 is much more dynamic and bass oriented, and the 1964-T is more smooth and neutral. The AC2 also has sharper more distinct highs, while the 1964-T is smooth and laid back in the upper region. This illustrates perfectly why we should not judge IEMs based on driver count alone. In any case, I was split down the middle as far as which model I liked best. For some rock like Jimmy Eat World I liked the smoother presentation of the 1964-T. But for classic rock like Hendrix the AC2 did a better job of bringing the performance to life. For electronic music I usually liked the AC2 better. For vocal oriented music I generally preferred the 1964-T for female singers and the AC2 for male singers, although that was not completely consistent. I mostly preferred the 1964-T for classical but again not every single time. I could go on but basically it is goes back and forth and probably depends on my mood as much as anything. The 1964-T is fairly similar in overall tone to the Kenwood KH-K1000 and somewhat similar to the Sennheiser HD600. In contrast, the AC2 has shades of Beyerdynamic and Denon full size headphones. I’m no Beyer expert, and I confess I’m not up on all the specific differences between the various versions (pre or post 2005 editions, 32/80/250/600 ohm versions, etc). But just in general the AC2 has similar bass quantity to the DT990, with a bit more control and authority to help distinguish between notes. The DT990 can feel a little “one note” at times. Mids are somewhat of a mix between the two models, veering closer to the DT990 overall but not as recessed or shallow sounding. Highs are also similar to the DT880 in that they are very sharp and not always smooth, and especially falter with cymbals. Soundstage is definitely DT990 with lots of space and definition. Another similar headphone would be the Denon D2000. I’ve only heard it a few times so I can’t say for sure if the AC2 is closer to the Denon or the Beyers.





This is what all clear cables eventually look like in my experience. It might take 8 months, it might take 3 years, or it might never quite get this bad.... but at least some green will definitely show up at some point. 





The Westone AC2 is a very interesting custom IEM. It sounds very different than I had expected, but I’m pleased with the sound that it offers. I have yet to hear the JH5 but compared to the original LiveWires, the UE4pro, the 1964-T, and the Unique Melody Aero, the AC2 stands alone. It is hit or miss at times; on some tracks the AC2 would be the last option I’d choose, but on many others it is my first choice. The key is figuring out what type of listener you are and how you want your music presented.


When Westone arrived late to the party with their flagship ES5, people were initially skeptical. Was Westone just trying to keep up in the “driver wars” with JH and UE? But I know of several very experienced members who now list the ES5 as their favorite IEM, above the highest offerings from the other companies. So obviously it was worth the wait. After a similar wait on the lower end of the range, I was hoping the AC2 would likewise dominate the competition. And it comes surprisingly close to doing just that. I’d go so far as to say that for certain people this is the absolute best choice for a sub $500 custom IEM. On the flip side, it would be one of the worst choices for other people. It just has a much more polarizing sound. I can see most people being satisfied with the UE4 or the 1964-T, even if they aren’t completely blown away. The AC2 would have some people being huge fans and leave others rather disappointed.


So who do I recommend this product to? People who love full, juicy mids should stay away. People who want tight subdued bass should look elsewhere. People who are overly sensitive to treble might want to skip it. If none of those things apply to you, the AC2 might be a good fit. If you enjoy the Denon D2000 or the Beyer DT880 and DT990, you are a very good AC2 candidate. Or if you are just willing to spend the time getting accustomed to a somewhat unique presentation, the AC2 could be a perfect match for you.





I’ve had the above review finished for almost a week now, and I’ve since had a few ideas worth mentioning. They don’t really fit in a coherent way into the review so I’ll just add them here.


1) I still feel that the AC2 is best played at lower to medium volumes. The dynamic sound and great isolation lends itself very well to that. But when moving higher, it seems to have more of a sweet spot than my other customs. By that I mean you can sometimes wish for more mids, then crank the volume only to find that the highs get too abrasive… But if you can dial it in just right you can get the mids just loud enough without overdoing it on the highs. This is best accomplished with a very precise volume control. I use the Anedio D1 headphone output, since the volume is controlled in .5dB increments. Something with bigger steps might not work so well, and a tiny volume knob won’t help either. This is not a consistent problem though and I don’t want to overstate it.


2) I recently picked up an Audio Technica W1000 and I think it has similarities with the AC2. Not in sound signature mind you, as they are very different. But they both seem to have their own areas were they excel. When matched with the proper equipment and music, they both give an extremely competent performance that in my opinion is hard to beat. And of course the opposite then becomes something to think about, which is that they both have areas where you could do better for the money.


3) As far as the idea and intent stated by Westone that the AC2 is a tool for performers to use, I think I agree with that. As a drummer I could certainly use these to perform, and I think people who played other instruments could too. But we could get a big discussion going here as to what makes a good monitor for performing versus just listening. For me I think the fact that they are dynamic, detailed, and great at medium volumes is what makes them work for me in theory. And for the price, you could outfit a whole band with matching customs without spending a fortune.


4) Much like the ES3X, the AC2 gets better on the high end with improved source and amplification. Running straight from a Sansa Clip+ gives a pretty good sound already, but the weak point in the highs is very obvious. As you move up the chain to higher quality equipment it becomes better. At no point does it become as good as the ES3X but it does move more in that direction.


5) I get just a hint of background hiss with these. It’s barely noticeable but it is there.


6) I’ll continue adding observations as I think of them, since this is not the easiest IEM to get a handle on. But I’m definitely enjoying it.






post #2 of 32
Thread Starter 


post #3 of 32

Well done - excellent review!! A very enjoyable read indeed with lots of interesting points discussed (at length). I don't think you left anything out. These certainly sound VERY 'intriguing'.


BTW, the TF10 is a dual-bore universal IEM.

post #4 of 32

I was wondering when you were going to write something up about the AC2. It sounds like an interesting custom where people who love it or hate it.


I do have a DT880 incoming so I wonder if it will be similar to the AC2 in signature :p

post #5 of 32

I know exactly what you mean by this:


When I use IEMs exclusively for a while and then switch to big headphones, I almost always feel like they sound too detached and distant for the first 10 minutes or so. My ears need to adjust to the physical space between them and the drivers. The AC2 sort of replicates that feeling.


Excellent review. Really enjoyed the cross-comparisons and your attention to detail. Great job!

Edited by SolidVictory - 5/7/11 at 7:49pm
post #6 of 32

Very nice read, I find the idea of a quite polarizing *sound wise* custom to be very interesting. I could see some people getting the AC2 without doing their homework regarding the sound and being quite unhappy which would put them in a bit of a bind regarding the whole custom thing. 

post #7 of 32
post #8 of 32
Thread Starter 

Thanks for the kind words everybody.


music_4321 - Thanks for the info about the TF10 being dual bore. I knew there were a few around but couldn't remember which ones specifically.


Rawrster - I'm interested to hear your thoughts on the DT880. Knowing your preferences, it's not something that immediately comes to mind as a good candidate for you. But then again you never know. Sometimes it is good to have a "contrasting opinion" so to speak, to give you a different take on things. The DT880 would do that as compared to your FA-003 or 1964-T. You might end up enjoying it.

post #9 of 32

Any chance you can compare to the Westone 4? Or the ES3X? ES3X is a bit of a lopsided comparison but still.

post #10 of 32
Thread Starter 
Originally Posted by ishmael View Post

Any chance you can compare to the Westone 4? Or the ES3X? ES3X is a bit of a lopsided comparison but still.

I have no experience with the Westone 4 so I can't compare. From descriptions though it sounds like the 4 is more balanced and well rounded. That would make it a better choice for some but not for all. I've heard people call it "perfectly good sounding yet kind of boring" and things like that. The AC2 would never get a comment like that - you'd either love it or dislike it.


An informal comparison with the ES3X: They sound very different. The ES3X has way more focus on the mids,which makes for a more intimate up close presentation. Snare drums have way more body. AC2 seems distant and detached in comparison. Bass on the ES3X is more controlled and tight, yet at times I wish it was a little more robust like the AC2. Listening to acoustic bass sometimes seems more realistic on the AC2, especially the very low notes. ES3X can sort of bury the bass in the mix at times.


So while I generally think the ES3X is superior, I choose the AC2 for some music. Classic rock that was recorded a little bright/thin sounds better with the AC2. And "ambient" electronic music like Mark Houle is great on the AC2. ES3X seems a little too in your face on that stuff, while the AC2 has a better flow, and is more relaxed.


I'm rambling but I hope that gives you a general idea. 


post #11 of 32

Holy crap this review got buried quick.


Bumped for visibility.

post #12 of 32
Yes, a most excellent review.smily_headphones1.gif
post #13 of 32
Thread Starter 

Thanks! Yep, the "portable headphone, earphones, and in ear monitors" forum moves very quickly.

post #14 of 32

Thanks for the review Project86! I just got my impressions done today and placed an order for the AC2's. They will be replacing my UM2's, which I am quite happy with, other than having to buy a new set of Comply's every week to keep a consistent fit. I feel like I'm renting my earphones sometimes haha.  They will be used the majority of the time as stage monitors, but I plan on using my iPod as a source sometimes as well.


You're review reassured me that I was making a good decision, as I love my UM2's. Thanks for the contributing so much to HeadFi... and all of us newbie's out there haha!

post #15 of 32

I just saw this; great review!  From your description they seem like they are different as most customs I have heard and have read about don't offer a V shaped sound signature.  And your description of who you would recommend the product to seems similar to how I would recommend the TS842!


Keep up the great work!

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