Custom IEM Review: Ambient Acoustics AM4 Pro
I first found Ambient Acoustics in my search for custom IEM manufacturers in 2011. At that time flagship product was the AM2. I contacted them in English to get more info but never received a response and let it go. Once I found out they now had 3 and 4 driver models so I decided it was time once again to reach out, but this time in Russian thanks to a friend. This time I did receive a response and found out more. The regular models have enhanced bass while the pro models are more of a reference design.
In my email exchanges with them, all in Russian, they told me they are interested in selling internationally and can take orders in English. After further communication, I was sending in my ear impressions for the AM4 pro. I chose between the bass enhanced AM4 and the more neutral AM4 pro, and decided on the neutral presentation since I know how good something neutral can sound when done right. All of this was done in Russian, but their site is supposed to be updated with English also, and a way to order internationally. A few months later the monitors arrived sans the typical accessories, as they informed me they would be sending only the monitors.
How to Order, Warranty, Options
Ambient Acoustics website can be found here, and although it is in Russian, Google Chrome will automatically translate it for you (or ask if you want it translated). They can communicate in English, Russian, and Ukrainian, however currently their order form is only in Russian and since it is a PDF, it can’t easily be translated in Chrome.
Options: The cable can be black, white, beige, or silver. There is an option for cable down configuration, however the cable will not be detachable. Artwork.
Warranty: 30 days for fit, 1 year for parts.
Design and Fit & Finish
The AM4 pro uses 4 balanced armature drivers in a 3-way configuration with an acrylic shell, 3 sound tubes, and has a detachable cable. The cable is non-standard; see the cable section for more information.
The outside finish of the AM4 pro is very nice, with no external artifacts, a perfect fit from my impressions, and the canal length is longer than many others such as the JH16 and IERM while not as long as the musicians fit 8.A or the SE 5-way. In other words, the canal length is a great length that allows for quick insertion along with a better seal and noise isolation than the shallower insertion CIEMs. Note that I do make ear impressions that are very deep.
On to the internal build of the AM4 pro. The internal drivers and electronics are well organized and positioned. The internal portion of the shell isn’t perfect, as upon close inspection the inside of the back plate is not smooth. This doesn’t affect the overall quality look or detract from the outward astetic qualities of the AM4 pro unless you inspect it closely and compare it with something that is smooth both inside and out, such as the Dunu DC4 and Heir Audio products. Fit & finish score: 8/10
The AM4 comes with a Dolphin case, cloth pouch, cleaning tool, and desiccant, however my AM4 pro only came with a cloth pouch, so I have used the accessory images from the Ambient Acoustics site.
The cable is unlike any custom IEM cable I have seen before as it is similar to that of the clear MEElectronics M6 cable, but thicker below the Y-Split. This cable appears more durable than a standard custom IEM cable, but the cable has a mind of its own, being very elastic and not wanting to stay wrapped. While that is a problem when trying to put the AM4 pro away, the cable is OK when in use. Ergonomics of the cable are similar to the Minerva and better than the i9pro, plus you can replace the cable if the ergonomics bother you. This is a clear cable that won’t turn green over time and does have a robust feel.
Isolation is a bit above average for an acrylic shelled custom IEM with a hollow shell due to the slightly longer than average canals. 6/10
Disclaimer: My review is a comparative review, and since I have many similarly priced custom IEMs, my perspective is based on equal competition. My goal is not to tell you how great the product under review is, but to explain the sound signature and characteristics as well as bring you a balanced account of the strengths and weaknesses to help you decide if this particular custom IEM is for you. This critical look at the product will almost always result in both strengths and weaknesses being revealed. It is my firm belief that you should buy a product based on the sound you prefer, or the sound for your particular purpose. If you don’t know what you want, read through the reviews and try to imagine if you would like the described aspects of the sound.
The AM4 pro received 100+ hours of burn in as is customary before I do my serious listening. The following custom IEMs were used for comparison: Dunu DC4, Alclair Reference, Fabs Fabulous Earphones, Thousand Sound TS842, Minerva Mi-3, Dream Earz aud-5X, and Wan Xuan i-9pro. After comparison with the previously mentioned CIEMs, Even though in different price points, I decided to also compare with the Ultimate Ears IERM and ACS T1 Live! as well as the Vsonic GR07.
The AM4 pro is designed with a balanced sound across the spectrum and upon my first listen that is what I got. I was pleasantly surprised with the overall sound quality and the sound signature balance gave a great tonality to the presentation with no glaring weaknesses. The monitor was very listenable out of the box. Over time I didn’t hear much, if any change, however I really didn’t listen for any.
Bass: Bass is near neutral with a slight lean to the enhanced side, but quite capable with the ability to recreate slam, rumble, and impact when the track calls for it. If you think the CK10 or ER4 have neutral bass, the AM4 pro will seem enhanced, however it is more that those two don’t have the capability to sustain bass notes to produce the full body and weight that is in the original track. While the bass is close to neutral, the dynamic range can make bass heavy tracks sound enhanced compared to many lower cost headphones and IEMs that don’t have the dynamic range that the AM4 pro has. The bass output capability is impressive for the sound signature and price level, but does trail the two dynamic driver CIEMs I have in the price range and the aud-5X. But the difference isn’t huge with a source that has driving power.
Detail levels and texturing is very good with the ability to rumble yet recreate the small nuances within the music from the well controlled drivers. It is not necessarily warm, nor lean, just neutral. Speed is excellent with the ability to keep up with just about anything, but it isn’t the fastest out there, which is a tradeoff due to the other fantastic qualities. The bass starts to gently roll off at 30 Hz, providing sensation down to 16 Hz and still having good weight at 20 Hz. While not the highest performing in the bass department, the combination of control, detail, texture, and capability place it in the to p 3 within the price range.
Midrange: Compared to reference monitors such as the Alclair Reference and IERM, the midrange is more forward and quite similar to a presentation such as the ACS T1!, which is a stage monitor. Many CIEMs in the price range are more mid-forward such as the DC4, Fabs, Mi-3, and SA-12 for example. Depth of the presentation is the best in the price range, close to the EM3 Pro, which allows the AM4 pro to image well and present music with excellent layering. Compared to others within the price range, the resolution within the soundstage, instrument separation, and instrument detail are all above average. Tone of vocals is spot on with both male and female vocals, providing a balance of clarity, warmth and brightness to vocals that all in a beautiful balance, not overdoing or under doing any part of the spectrum. Integration and balance of the midrange with the rest of the spectrum is excellent. The bottom line is the midrange is immersive, accurate, and musical with a presentation somewhere between a stage monitor and studio monitor.
Treble: Rounding out the balanced frequency response, the treble provides a bit of brightness, but not to the level of the IERM and TS842 and has more treble presence than others such as the TS842 and DC4. The treble has air, detail, good extension, and very good note attack and decay leading to a pleasant, articulate, and realistic sound. Detail levels are good considering the note decay, as brighter sound and faster decay accentuates the details, but doesn’t sound as natural. With a high quality, natural sound, the treble provides the finishing touch to the excellent presentation across the entire frequency spectrum.
As the source quality decreases and/or the volume increases, the treble becomes more analytical and sharper, reducing the overall quality that is so good at lower volumes.
Presentation: Every part of the frequency spectrum comes together quite well While there is nothing wrong with any part of the frequency spectrum, the real strength of the AM4 pro is the overall presentation. Everything is integrated together quite well resulting in great coherence. The forward midrange gives more of a stage monitor sound than a studio reference monitor, but it could still work for the studio. Depth of the presentation is impressive, rivaling CIEMs with prices over double, but the width is more reminiscent of the price range. This impressive depth of presentation, like the bass, doesn’t come through unless it is in the recording, so it doesn’t sound off when tracks don’t have the depth.
Note decay is not analytical, but not too smooth; a nice balance that is detailed, but not in an analytical way. In a similar fashion to the presentation depth, the AM4 pro is one of the better performers as far as detail and resolution goes, but still lags behind CIEMs at double the price and more. The AM4 pro is revealing yet forgiving of poor tracks. Speed is fine for all genres, and while it doesn’t sound slow, other CIEMs such as the 5X, TS842, and more expensive CIEMs have a better sense of speed. Dynamics are excellent and transparency is above average.
Reference Master: While there are distinct differences, these two both present with a balance from top to bottom, not overdoing any part of the spectrum. From a soundstage perspective, the AM4 pro presentation is more mid-forward with similar width, but the AM4 pro has a good deal more depth to the presentation, better clarity and slightly better resolution within the soundstage space. The Reference does have better instrument separation and more black space between instruments resulting in better imaging, but the left to right coherence results in a lack of a fill in the middle part of the soundstage. The AM4 pro advantages result in a more realistic and immersive experience. Instrument detail levels are close, but the AM4 pro edges out the Reference by a bit and also has better dynamics. Transparency is very similar between the two and the Reference is slightly more forgiving.
Due to the more upfront presentation of the AM4 pro, the bass is a bit more up forward resulting in the perception of more bass emphasis when comparing the two, however in relation to the rest of the spectrum, the bass is similarly balanced. The bass, and especially the deep bass is more palpable with the AM4 pro, as the bass drivers have more ability to kick and rumble. Warmth is very similar. The vocals of the AM4 pro are more prominent, cleaner, and clearer. Even though the midrange is further back with the Reference, the upper midrange on up is close, which gives more emphasis to the Reference than the AM4 pro, if just by a bit. Since the AM4 pro has a better soundstage focus, the treble is cleaner, although pretty close in quantity. Note decay in the treble is close, but the AM4 pro does have a slightly longer note decay that sounds more natural.
With similar but different sound signatures, and considering the price, these two might be best being purchased from their respective regions: the Reference for people in the US and the AM4 pro for people in Europe. In a nutshell the Reference gives you a more laid back sound with a better overall presentation while the AM4 pro is more upfront with better instrument detail and dynamics resulting in better engagement within the presentation. The Reference represents someone in the audience listening to a presentation while with the AM4 pro you are involved in the performance.
Aud-5X: Tonal differences and presentation give these two different feels and sonic signatures, with the aud-5X having a more spacious presentation while the additional upper midrange of the AM4 pro give it a brighter feel. Both have spacious soundstages, but the AM4 pro has a good deal more depth to the presentation than the 5X. Even with a thicker note and smoother presentation, the 5X is slightly more detailed with more resolution of the overall presentation. Dynamics are fairly close, but the 5X pulls ahead while the AM4 pro is the easy winner in clarity and imaging. Speed is similar and transparency goes to the 5X. The AM4 pro is pretty forgiving, but the 5X is even more forgiving of poor tracks.
The three bass drivers of the 5X can really generate some rumble and impact, and while the AM4 pro isn’t bad in this region, bass heavy songs have noticeably more weight with the 5X, which also carries over to the mid-bass warmth and thickness. The midrange of the AM4 is more forward and engaging while in comparison the 5X midrange seems a bit recessed, yet still thicker and not providing quite the clarity. The upper midrange of the AM4 is in line with the midrange, but with the 5X it seems a bit more pronounced in comparison with the midrange. The treble of the AM4 is more pronounced while the 5X treble is a bit smoother, yet still retaining the detail.
These two are very different in presentation, but not in capability. The AM4 is more forward, brighter presentation that has neutral bass and nice clarity while the 5X is quite capable in the bass region and will satisfy those looking for a smoother and thicker presentation across the spectrum. They complement each other well and both have exceptional performance considering the price.
i9pro: The AM4 pro has a more intimate presentation compared with the more open, spacious, and laid back presentation, the i9pro. The soundstage is a good deal wider, but not quite as deep as the AM4 pro, resulting in a different feel. And the FST technology of the i9pro does add depth, but the depth is different than typical. Imaging and placement are better with the AM4 pro, giving a better focus of the overall presentation vs. the more spacious sounding i9pro. Instrument detail levels are about the same while the resolution of the presentation is better with the AM4 pro. They both have a natural note attack and decay, but the AM4 pro is quicker while the i9pro can sustain a note better. Dynamics and coherence favor the i9pro, but the AM4 pro is more clear and transparent.
Bass of the i9pro is hits deeper, is more enhanced and more capable, giving a more powerful and bass skewed presentation. The i9pro is also warmer that leads up to a more relaxed midrange. The AM4 pro midrange is clearer and more concise as well as more intimate. The upper midrange and treble of the AM4 pro are more prominent, leading to a brighter sound and less variance of brightness between tracks. The i9pro did sound a bit dark in comparison with the AM4 pro in a few tracks.
With two very different sound signatures, the AM4 pro and i9pro will hit different markets. The AM4 pro is for those that want a more reference sound and more intimate presentation, and brightness. The i9pro will satisfy bass heads and those that want a warm, lush, and non-offensive presentation.
Fabs: The Fabs share a mid-forward presentation with the AM4 pro, but the Fabs aren’t quite as forward nor do they have the same technical ability. Overall there are quite a few differences, with the AM4 pro providing a full range presentation from top to bottom while the Fabs is more of a mid-focused presentation that doesn’t convey the entire presentation. The Fabs soundstage isn’t as wide or deep, the detail levels are less, there are less dynamics, imaging isn’t as good, and the focus within the soundstage falls short of the AM4 pro. The Fabs competes quite well with select tracks, but with the majority of my tracks display a large discrepancy. But it is not all bad for the Fabs as the clarity levels are close to the AM4 pro and coherence and transparence is actually a bit better. The AM4 pro is more forgiving of poor tracks even though it is brighter.
There are huge differences in bass levels as the Fabs are not a full shell and don’t insert deeply into my ears. The AM4 pro is more capable and fuller in the bass region while the Fabs become thicker in the midrange. Midranges are similar, but the Fabs is more liquid in the midrange but with lower detail levels, which is good for some tracks in comparison but not for most. Vocals are have a nice quality to them with the Fabs while the AM4 pro sounds more realistic and detailed. The Fabs treble slowly rolls off at a slow rate while the AM4 pro treble is more extended, but the Fabs has a thicker, smoother treble note which prevents cymbals from really shimmying. This gives the AM4 pro an air feel in comparison.
The Fabs will appeal to some, in part for the inline mic/remote capability, in part because of the music they listen to, which would be classical and easy listening/vocal type music, and in part due to the half shells. Paired with an iPhone, the differences are smaller than a high end source, but the AM4 pro still wins technically. Unless you have specific needs mentioned above or are treble averse, the AM4 pro is the better choice.
Mi-3: With a more distant and overall more spacious sound, the Mi-3 has a more laid back presentation that puts you in the audience. Given the difference in presentation location, both share forward mids, but both ends of the spectrum are quite different. The AM4 pro has a nice balance across the spectrum while the Mi-3 seems a bit rolled off on both ends. Technically the AM4 pro is superior in most ways including dynamics, detail, clarity, and speed while transparency and coherence are similar. Dynamics are a bit one, as the AM4 pro sounds more alive and punchy to go with more depth of the presentation and more refinement within the soundstage.
Both ends of the spectrum sound a bit lacking from the Mi-3 in comparison with the AM4 pro, and bass heavy tracks are significantly different, especially in rumble and impact. The thicker note of the Mi-3 and not as bright of a performance gives the Mi-3 a warmer presentation. The AM4 pro midrange is not only closer to you, but more detailed, cleaner, and clearer. The upper midrange and treble of the AM4 pro is a good deal more prominent, which is responsible for pulling the presentation forward. Overall the quality of both is very good with nice smoothness, but the Mi-3 is more liquid while the AM4 pro is more detailed and resolving.
The AM4 pro and Mi-3 have different feels, with the AM4 pro having a brighter, yet more bass capable sound that is more up front, especially in comparison with the laid back yet mid-forward Mi-3. Bass presentation is significantly different, as is the treble. The Mi-3 would make for a good casual listening CIEM if you don’t have bass heavy tracks while the AM4 pro is great for hearing more within the presentation and those that want a more upfront and involving presentation.
TS842: These two are quite a bit different with the TS842 having more of a U shaped frequency response while the AM4 pro is more mid-forward. Even with a more mid-forward presentation, the AM4 pro has a bit wider soundstage and a good deal more depth to the presentation. The TS842 is analytical in the midrange on up and the dynamic bass driver is a quick and accurate driver, but still has a richer and thicker presentation while the AM4 pro is more consistent from top to bottom in note thickness. This give the AM4 pro a significant lead in coherence while dynamics and detail levels are slightly better with the TS842. With a more prominent midrange, better imaging, and a sharper focus within the soundstage, the AM4 pro has better clarity. The AM4 pro is a bit more transparent and slightly more forgiving of poor tracks.
Bass is usually similar, but there are times when a song has deep, reverberant bass where the TS842 has an altogether different feel due to the dynamic bass driver. This feel conveys more power as well as better texturing, yet the bass of both is quite neutral. Overall the TS842 does have a bit more bass and warmth. The midranges are very different as the AM4 pro has a bit of a forward midrange while the TS842 has a laid back midrange. This results in a more engaging presentation from the AM4 pro and the better imaging, presentation depth, and focus make for a more involving midrange. The upper midrange of both is different in that the AM4 pro upper mids are an extension of the midrange while the TS842 has a ramp up, making that section brighter with the AM4 pro. However, once you get into the treble region, the TS842 is brighter in relation to the midrange. Both have an analytical edge to the treble, but the TS842 more so.
Choosing between the two should be easy…do you want an up-front presentation or a laid back one? All else is minor differences on top of those major differences. Things such as the bass power of the TS842’s dynamic driver, or the involving midrange of the AM4 pro. But, both stopped me from reviewing to just listen.
DC4: The upper midrange and treble presentation take these two in different directions as the AM4 pro is brighter in comparison with the slightly bass enhanced and warmer DC4. Both present very similarly other than the warmth and brightness differences, however the AM4 pro is a good deal clearer due to the added brightness. Size wise, the AM4 pro has better depth and width which gives the DC4 a more personal presentation, however imaging is close. Detail levels and resolution within the soundstage are close, with the DC4 pulling slightly ahead of the AM4 pro in both. Combining the presentation and clarity with a slightly better focus, the AM4 pro sounds clearer and makes the DC4 sound slightly veiled in comparison. The DC4 also has better dynamics, coherence across the frequency spectrum, and transparency, but note attack and decay has more range with the AM4 pro resulting in a more realistic note and a bit more speed for fast music. The DC4 is more forgiving of poorly mastered tracks.
While the DC4 has more bass, both in enhancement and in capability to output rumble, the AM4 pro isn’t too far behind and has a much tighter low end that has better texturing. The DC4 is warmer and thicker throughout the entire presentation. While the midrange is presented similarly, the larger soundstage of the AM4 pro gives a more open and spacious feel in comparison with the intimate and somewhat veiled DC4. The upper midrange on up through the treble of the AM4 pro is more pronounced resulting in a brighter and clearer sound. Quality is good with both, but the AM4 pro sounds more realistic.
Both share their presentation style, but offer different flavors, with the AM4 pro having a brighter presentation wrapped in a larger overall soundstage that is more neutral while the DC4 is more intimate with more bass emphasis and warmth. Neither makes the other sound bad, and it comes down to what you are looking for and availability. Technically they are close, but the AM4 pro edges out the DC4.
T1 Live!: The AM4 pro puts you closer to the performance with a more mid-forward presentation, but the spaciousness combined with the forwardness of the presentation grabs you more than the T1. Tonality is quite close between these two. The T1 Live! has a bit wider presentation but the AM4 pro has better depth of presentation. The T1 Live! bests the AM4 pro in clarity within the soundstage, although both suffer from reduction in clarity within the soundstage at louder volumes. Dynamics of the T1 Live! are a better in the mids and treble while the bass dynamics of the AM4 pro are superior. The AM4 pro has a bit more speed to the presentation and is more forgiving however the T1 Live! is more transparent and coherent.
The AM4 pro bas more kick down low with better extension and more weight for bass heavy songs. The quality of the bass is a bit better with the T1 Live!, but given the AM4 pro can output more bass, that is a limiting factor for the T1 Live!. Warmth is quite similar. The midranges are where the two diverge the most as the T1 Live! is more laid back and gives a more airy, wide presentation while the AM4 pro is more up-front and personal with exceptional depth of presentation. Resolution and detail levels are a bit better with the T1 Live! There is a bit more treble presence with the T1 Live! while the AM4 pro treble sounds more natural and of higher quality.
Essentially, the AM4 pro is a more mid-forward, slightly less bright, and more bass capable version of the T1 Live!. Now, it isn’t as simple as that, but the comparison is there. Of course, the T1 Live! is easier to get, easier to service, uses silicone, and has mics for ambient feedback, but from a pure sound perspective, the price difference and not too large sound differences should make you think.
IERM: Both are reference monitors, so I decided to compare the two despite the price difference. The overall presentation of the IERM is larger and makes the AM4 pro sound mid-forward in comparison. Detail levels and attack/decay capability are close, with the IERM slightly edges out the AM4 pro in both. Transparency is better with the IERM, but the AM4 pro is more coherent. Dynamics are similar, except in the bass where the AM4 pro pulls ahead of the IERM. Imaging and soundstage space are superior on the IERM even though the AM4 pro has excellent soundstage depth, the overall size doesn’t quite compare. Clarity, while very good with the AM4 pro is bested by the IERM.
The AM4 pro outputs a larger quantity of bass that extends deeper conveying more power with better bass detail and has slightly better texturing. While not necessarily warm, the AM4 pro is warmer than the IERM. With a more mid-forward presentation, the AM4 pro’s places vocals closer while giving them a more clear and concise presentation, but with a bit more upper midrange and treble presence, the IERM is overall clearer with a greater sense of air, however with anything but the best mastering, the IERM is much harsher than the AM4 pro to my ears.
Fans of bright and spacious will prefer the IERM vs. the more mid-forward and balanced AM4 pro. The IERM does outperform the AM4 pro from a technical ability standpoint, but the AM4 pro offers a presentation that combines a musical performance with analytical flair. Those that want more bass will prefer the AM4 pro even though both are fairly neutral. The IERM has more of a monitoring sound while the AM4 pro would be better on stage.
GR07: This comparison isn’t focusing on the higher levels of detail, better clarity and dynamics, etc., but instead on the sound signature differences. The upper bass of the GR07 is more prominent while the deep bass rumble and performance is similar. The midrange of the GR07 is more laid back while the AM4 pro has more prominent upper mids and an overall brighter presentation. The presentation space of the AM4 is larger in both width and depth. Due to the higher resolution/detail levels, the AM4 pro is more revealing of both details within the presentation and poor sound quality of bad tracks. Essentially, the AM4 pro is brighter and more mid-forward while offering more detail, space, dynamics and clarity with similar bass reproduction.
Volume performance: The AM4 pro excels at low to medium volumes, with a full sound at quieter volumes than most BA CIEMs. At extremely low level listening the AM4 pro has similar issues to other IEMs, which is there isn’t enough power to generate enough power for a full sound. As you turn the volume up the exceptional clarity, focus, and resolution within the soundstage start to get a bit congested in comparison with the lower volume levels. This loss in clarity isn’t to the extent of some others I have heard, but is still there. The treble that is smooth and liquid, yet detailed at low to medium volumes becomes a bit harsher at louder volumes. I can’t listen at the volume where there are issues for more than a minute or two.
Sound Summary: The AM4 pro has a sound signature that is on the brighter side of neutral with a very good balance and integration across the frequency spectrum. The midrange is presented in a forward way, more forward than the reference monitors I used for comparison, but not as forward as some of the audiophile models, which make it great for stage use as well as a reference, or just for music enjoyment. The bass is very capable, the midrange has an impressively deep soundstage, clarity is great and resolution is high for the price while the treble has an excellent note decay, all leading to a tonality that just sounds right. From a technical performance standpoint, the AM4 pro punches above its price and holds up quite well when compared with monitors double the price. Overall, the AM4 is an impressive custom IEM that will please many.
Portable Sources, DAPs
Clip+: The Clip+ offers decent sound one would expect when combining the Clip+ with the AM4 pro, good but not great sound. Dynamics aren’t what they are with an amp or a better source, and the overall soundstage is a bit small and doesn’t have great depth. Deep bass is surprisingly not as powerful as with the iPhone 4S, or even the RoCoo BA. 3/10
iPhone 4S: With a brighter and more spacious presentation than the Clip+, the iPhone has many advantages, which also include better bass power resulting in more emphasis and rumble. The overall space is larger and the depth of presentation is also better. Detail levels aren’t quite as high as the Clip+, nor are dynamics in the midrange. Overall a good presentation considering the convenience factor. 4/10
RoCoo BA: Adding a slightly more spacious sound and better dynamics than either the iPhone 4S or Clip+, the BA presents with a bit more forward midrange and a more refined, smoother presentation. Detail levels are higher, but not to the level of the 801 or DX100. Not bad, but not the best. 5.5/10
801 (with GAME card): The 801 opens up the AM4 pro and allows it to show what it is capable of, taking the performance up a notch. Bass is more authoritative, depth of the presentation as well as the overall space improve significantly, and detail levels increase. The combo isn’t overly bright and does sound like the treble is laid back in comparison with other sources, which sounds fine with some tracks and not the greatest with others. The treble of the 801 with the AM4 pro can be rough and less than the smooth and musical presentation of other sources including the RoCoo BA (although it bests the BA in many ways) and the iPod-> 627. While the 801 doesn’t bring the AM4 pro to the level of CIEMs that cost double, it does close the gap. 7/10
DX100: The DX100 takes what the 801 does and improves upon it. Depth of the presentation is better and the sound is more natural, smooth, and flowing resulting in an incredibly involving presentation. While the 801 can be harsh with poorly mastered tracks (some of my pop and metal favorites), the DX100 isn’t nearly as offensive. Overall, the sound isn’t quite as spacious as the 801->627, but the differences are minimal and for one unit, it is quite good. 9.5/10
Portable Sources, DAPs with Amps
iPhone 4S ->
i.Fuzen amp case: The i.Fuzen is not as bright as the HPO, and therefore gives a more bass heavy presentation. The i.Fuzen ever so slightly improved the overall sound quality, but I mean slightly, however the darker, more bass heavy sound changes the character of the AM4 pro quite a bit. This can be good or bad depending on what you want from the AM4 pro. 4/10
Pico Slim: The PS adds a bit of brightness over the HPO, but also adds presentation depth, but has a slightly smaller presentation. The overall presentation is cleaned up a bit by the PS, adding a bit to clarity. With a smoother presentation and more resolution, the PS is more musical and transparent than the HPO. 5/10
627: The 627 opens up the presentation, making it more airy, laid back, and spacious with better depth of the presentation. The resolution is improved and the entire presentation sounds more realistic as details are easier to make out within the layered presentation, bass is more controlled and authoritative, and the tonality sounds quite right. 6/10
Modded iPod -> Overall the modded iPod doesn’t convey the spatial information the AM4 pro is capable of from the 801 and DX100, and the RoCoo BA also has a bit more depth.
Neco V2: Decent spaciousness and control of the presentation, but after listening to the DX100 for an extended period of time, the V2 doesn’t have the spaciousness, control, or clarity, and the presentation is more analytical, yet less detailed. But, considering this setup cost less, a good deal less, it is better than the similar setup from an iPhone. 5/10
Shonyun-306: The 306 is a bit more forward and smaller in presentation width than the V2 with less bass impact and control, but has a bit more depth to the presentation and is slightly brighter. Treble isn’t quite as smooth as the V2. 4.5/10
EPH-O2: The O2 is a much better match with the AM4 pro than the V2 and 306, with a smoother and more refined top end, wider presentation that is a bit more laid back with better depth. The is better refinement within the larger presentation space also consists of having more reverb with string instrument resulting in a more natural sound. This setup is more spacious than the RoCoo D, although the RoCoo has more depth in proportion to the soundstage width and has a nice air and smoothness to it. There is a channel imbalance, so I had to turn the line out volume of the iPod down to eliminate it (-1 point to the score). 5/10
uHA-120: The O2 is slightly more spacious than the uHA-120, and the treble is a bit more laid back and smoother, although the uHA has a bit better depth to the presentation along with a slight bit better clarity within the soundstage. Bass is tighter and punchier with the uHA, with less quantity, especially in the mid-bass. There is a channel imbalance at low volumes (-0.5 points to the score) 6/10
Arrow 12HE 4G: With a more laid back and spacious presentation, the treble is relaxed and there is more emphasis on the mid-bass compared with the uHA-120. Overall the uHA is a bit cleaner than the 4G with more depth to the presentation space and deep bass more prominent. There is a severe channel imbalance at very low volume levels (-0.5 to the score) 5.5/10
Pico Slim: The Pico Slim adds a fullness to the presentation giving it a richer presentation in addition to brightening the sound in a clean way. The presentation of space is better overall than all the amps listed above with both depth and width. Resolution within the presentation isn’t the highest, but what is there is very clean and well controlled. And speaking of control, the PS has better control than the 4G and uHA. 6.5/10
Stepdance: The SD has a nice balance across the spectrum and doesn’t do anything wrong, but the PS does best it in depth of presentation while keeping up with it in everything else, but surprisingly the PS has a bit more deep bass punch and slightly more control. Clarity of the presentation is about the same. The SD is not quite as bright as the PS, but it isn’t too far off. 6/10
Cruise: While the cruise has a very dynamic presentation that really adds excitement to the AM4 pro, there are issues. The amp is more spacious than the PS or SD by a bit, a little cleaner, but there is hiss and a very minor very low volume channel imbalance that keep the Cruise from being a strong recommendation for the AM4 pro. Other than those two things, the amp performs quite well, although it does brighten the presentation. (-1 due to hiss) 5/5/10
627: The 627 is more spacious and fuller than the PS, which is the 2nd best performing amp in I have. The entire presentation is cleaner and smoother, which is most noticeable in the treble. The 627 has better layering than the PS, but the real thing holding it back in this combination is the iPod. There is an ever so slight channel imbalance at very low volumes. 7/10
Pico Slim: The PS brightens the presentation giving it a sound that is closer to other sources. The overall presentation is better than the HPO as it is a bit smoother and more forgiving, but not all that much. The overall presentation is a bit more mid-forward and slightly smaller. 7.5/10
627: The 627 simply takes what the 801 does and improves on it in every way, including brightening the presentation up. Bass is tighter yet more prominent when the track calls for it, space is greater and the overall sound is more airy, more detail comes through, and the overall sound is more refined, involving, and engaging. 9/10
HUD-MX1 (OPA1611): Due to the high sensitivity of the AM4 pro, my MX1 has a channel imbalance at low to moderate volumes. Unfortunately this takes away from what is a decent pairing as the MX1 is quite neutral and detailed with decent depth. Bass is well controlled and the treble is smooth and pleasant yet still detailed. Space is on par with the more expensive Cruise, although dynamics aren’t at the same level. (-1 for imbalance) 5/10.
Cruise: As with the pairing with the iPod, the Cruise sound punchy and nice except for the hiss and slight channel imbalance. The details and speed of the DAC + amp lead to a less forgiving treble, which takes away from the presentation. I could recommend this combo as the sound isn’t that bad, but the hiss is disappointing. (-1 for hiss) 5.5/10
D1: While the DX100 and 801 sound exceptional with the AM4 pro, the D1 is more spacious, specifically in the depth of presentation. Bass is powerful and well controlled resulting in an amazing sound for the price of the AM4 pro. Compared with the 801 -> 627, the D1 isn’t too far behind in soundstage size and overall resolution, but does have slightly less layering. 10/10
Source Summary: The AM4 pro is very scalable: feed it from a better source chain and you will get better results. The difference between the highest and lowest performing sources is quite large and the AM4 pro is selective about the amps/sources it pairs well with. Sensitive being on the high side brings out low volume balance issues for many amps. If you feed it from an average source, the performance will be in line with the price, but pairing it with a higher end source, the AM4 pro can punch above its weight. A better source can, depending on the synergy, help tame the clarity within the soundstage and the treble smoothness, both of which are weaknesses of the AM4 pro with lower end sources.
The Ambient Acoustics AM4 pro is an exceptional performer at the price point with a relatively neutral and very natural sound that works for the stage, studio, or just enjoying music. Note decay is very realistic, the soundstage is very 3D with exceptional depth, and dynamic range is impressive, all resulting in a presentation that immersive and engaging while staying neutral but still musical. When supplied by a high quality amp, the AM4 pro can compete with CIEMs that cost double as it scales very well. However, with lower end sources and at louder volumes the clarity can suffer as complex material becomes slightly congested. Overall the AM4 pro performs admirably and will surely develop a following due to the sound quality and value.
- Very capable in the bass region with great dynamics throughout the frequency spectrum
- Exceptional depth of the presentation for the price range
- Note decay is very natural from top to bottom with a blend of detail and liquidity resulting in an extremely musical, involving, and believable presentation
- At louder than medium volume the clarity and quality of the presentation decrease
- The AM4 pro is sensitive to the quality of the source components, and treble refinement suffers with lower end sources