MMR Gáe Bolg

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Gáe Bolg

'Gáe Bolg' is engineered with linear acoustics in mind. Delivering incredibly immersive sound and beautiful spatial imaging. It presents an impeccable intimate presentation that's is incomparable invigorating. 'Gáe Bolg' features a bespoke vented mid BA that allows for an alluring mid-range vocals to flow through seamlessly while reinforced with a high speed tweeter to smoothen highs frequency and a XL low driver to spur on the level of energy. Housed within a MMR specialty Titanium shell for UIEM or high precision 3D printed acrylic shell for CIEM, the monitor is offers perfect ergonomics that is befitting of daily and professional usage. This IEM is one of the finest picks for single / dual instrumentalists, vocalist, engineers and audiophiles.

- 5 Precision Built Balanced Armatures
- 1 Tweeter , 1 Vented Mid-High , 2 Mids , 1 XL Low
- 4 - Way Passive Electro Frequency Division
- TriBore Waveguide

Frequency Response : 20Hz - 40kHz
Impedance : 20ohm
Noise Isolation : -26db (CIEM) / -18db (UIEM)

Retail Price : $1199

Latest reviews


Headphoneus Supremus
MMR Gáe Bolg - Balanced richness for endless joy
Pros: Rich and highly versatile signature that you can listen to all day (non-fatiguing), balanced but very musical, excellent imaging, build quality, very good and comfortable fit
Cons: Not for those looking for a technical signature
MMR Gáe Bolg

I would like to thank Joseph Mou for providing me with the MMR Gáe Bolg in exchange for my honest opinion. No incentive was given for a favourable review.

Gáe Bolg
  • 5 Custom Tuned Balanced Armature Drivers Configuration
  • 1 Tweeter, 1 Vented Mid-High, 1 Mids, 2 Vented Lows
  • 4-Way Passive Electro Frequency Division
  • TriBore Waveguide
  • GB Acoustic Chamber™
  • Frequency Response: 20Hz-40kHz
  • Impedance: 25ohm
  • Noise Isolation: -18db (UIEM)
  • Price: US$1,199 (Lite) or US$1,399 (Complete)

For a free 1-month trial of Qobuz visit:

Last year I introduced Metal Magic Research, or MMR for short, when I reviewed their unique flagship hybrid IEMs the Thummim. Named after a mythical spear, the Gáe Bolg continue the tradition at MMR to do things a bit different from others, be it this time at a much more affordable price point and with a balanced armature only design. Balanced also seems to be the name of the game with Gáe Bolg. Where the Thummim are unique, crazy even, with tons of energy and the most extraordinarily spherical soundstage I have ever heard, the Gáe Bolg feel more conventional, balanced and extremely versatile.

In fact, Gáe Bolg fit a category I recently saw promoted for the VxV by FiR Audio, which was termed ‘EveryDay Carry’, or EDC for short. I am not into the EDC scene, I can however imagine what IEMs would have to be like to fit into an EDC load out. Such IEMs need to have an excellent build quality to take everywhere, a comfortable fit for using them all day long and a versatile signature because you will want to listen to all your music using them. Gáe Bolg fit this to a T.


I have had Gáe Bolg over for quite a while now and had initially planned a regular review. However, because of the highly versatile nature of Gáe Bolg and coincidentally being offered a 3-month trial from Qobuz, I saw an opportunity to do something I have always wanted to do. We are in this hobby because of the music, yet our focus on gear tends to distract from that to a point where many often forget to enjoy the music. I have already started a review series dedicated to classical music where I put the music first and use the gear as a means to an end. In other words, the IEMs should be seen as the tools we use to enjoy our favourite music. For Gáe Bolg I wanted to spin that concept around and use their versatility to explore new music using Qobuz’s 70 million songs and over 220,000 Hi-Res albums. Yes, I copied Qobuz’s marketing line there, but the point here is that having versatile IEMs and a silly big catalogue of music to dive into must be an audiophile’s equivalent of skinny dipping into Willy Wonka’s chocolate river.

This is also why I kept delaying this review. I didn’t really want to write it because I was enjoying the music too much. I just wanted to keep going like an Energizer Bunny. I kept checking Qobuz’s new releases and album suggestions, friends kept sending me tips on what albums to try and some of those albums I just kept playing again and again because I loved them so much. I can write all the sound impressions I can think of (don’t worry I will write some), but this more than anything is a testament to how nice the Gáe Bolg are to listen to and just how versatile they are.

Reviewer’s privilege, I received the Gáe Bolg a little before their official release and for me they simply came in a metal round case without any packaging. MMR were however kind enough to send over pictures of the full presentation and they did a really nice job of creating something special. The box displays the IEMs neatly alongside a metal product card and a unique looking leather case. From what I understand a full set of Acoustune tips is included as well.



Images courtesy of MMR.

With the IEMs comes of course the cable and which one you receive depends on the version of the Gáe Bolg you bought. Gáe Bolg is offered in a ‘Lite’ and a ‘Complete’ version and the Lite comes with a regular stock cable, whereas the Complete comes with the premium Eletech Prudence. One added advantage of the Complete version is that you can choose the termination in standard 3.5mm single ended, 2.5mm balanced or 4.4mm balanced. The Lite only comes in 3.5mm single ended.

Build quality and fit
When I had Gáe Bolg in my hands for the first time, it struck me just how detailed and well thought out the design is. It is gorgeous to look at, feels great in the hand and a lot of attention must have gone into finalising the fit and finish. In no way do I feel this is any less than what you get with the flagship Thummim, despite the considerable difference in price.


The most obvious feature is the three-dimensionally designed faceplate that is CNC’d from aluminium and takes inspiration from the mythical spear after which the Gáe Bolg were named. The beautiful satin red colour with its sandblasted finish contrasting against the matt black backplate is incredibly well done and coincidentally nearly impossible to do justice in pictures. The other side is super smooth, also from aluminium and designed with optimised comfort that I think worked out really well. I have used the Gáe Bolg for countless hours and never experienced any discomfort from them.

Similar to Thummim, Gáe Bolg uses an acoustic chamber to control the tuning. I expect this acoustic chamber is once again 3D printed with great precision onto which the drivers are mounted.


Image courtesy of MMR

The stock cable is a very nice one, as far as stock cables are concerned. Nothing too fancy, but sturdy, comfortable and with nice parts. Of course when you go for the Complete version you get the Eletech Prudence included and that is a very nice cable. Prudence is a 26 AWG silver-plated copper that is clearly a step up from most spc cables. At 26 AWG it is a little thicker than the stock cable and because of how supple it is, you don’t notice the difference. The parts on Prudence are of a very high quality and gives a bit of added bling to Gáe Bolg.

Gáe Bolg Lite vs Complete
The big question with Gáe Bolg is of course whether or not it is worth paying the US$200 premium for the Eletech Prudence upgrade of the Complete version. Prudence usually sells for US$249, so you get a nice discount on it, and there is of course the option for a balanced termination in either 2.5mm or 4.4mm. But what about the sound?

In my opinion Prudence has a noticeable impact on sound quality. It doesn’t change the character of Gáe Bolg as such, I don’t think any cable can significantly affect the character of IEMs, but there are some improvements nonetheless. The stock cable has a somewhat warmer presentation. Prudence reduces that a little bit by tightening the bass and giving it more impact, which instantly gives Gáe Bolg a little more dynamics. Overall clarity is improved and the stage becomes larger both in terms of width and depth, and airier to give an even more spacious feel. The main benefit of this can be found in the imaging. Imaging is already good with the stock cable, but Prudence (in my opinion) elevates it to another level. Suddenly the music seems to be presented with more precision and better positional information, thanks in part to a blacker background.


I am not sure, but in all honesty I would not be surprised if Gáe Bolg were tuned with Prudence in mind. Although I am always reluctant to outright recommend gear, especially a cable, I genuinely think that it is worth considering the upgrade if your budget stretches that far. You won’t really miss out with the stock cable and some might even prefer the slightly warmer sound, but if you want to get the extra edge in performance then going for the Complete version is an excellent option.

As such, my impressions will be with Prudence to represent the Complete version.

I have used Gáe Bolg with a number of different sources and I honestly think they pair well with everything, although I personally like them especially with a more analogue sounding source such as the Shanling M8.

-Dethonray Honey H1-
The Honey H1 is a USB DAC/amp and a darn good one at that. I don’t think it quite gets to the level of the higher end sources I use, but it is a great performer for its price. The Honey H1 worked wonderful for streaming using my MacBook Pro.

With the Honey H1 the Gáe Bolg get a lovely smooth presentation that is easy-going and has a fluidity to the notes that makes them especially pleasing to listen to for longer periods of time.

-Lotoo PAW Gold Touch-
A recent addition to my DAP stable and the highest performer of the DAPs. With the LPGT the Gáe Bolg get a crisper and clearer presentation with more bass impact and overall a more dynamic feel. The stage is larger and more airy, and the background gets Lotoo’s trademark deep darkness.

-Shanling M8-
My primary streaming DAP for reviews. The M8 gives the Gáe Bolg a more analogue sounding low end with a bit more growl. The Gáe Bolg get a highly dynamic presentation with a smoothness similar to the Honey H1, but with a bigger and more airy stage.

-Violectric V380-
The Violectric V380 is a neutral high-end desktop DAC/amp and I used it primarily for comparisons, as it has two 6.3mm SE headphone outs, making it particularly useful for A/B-ing. The V380 scales the Gáe Bolg very nicely, imbuing them with more dynamics, a bigger stage and more air.

The Gáe Bolg are wonderfully balanced IEMs that I feel show something I would describe as an exercise in moderation. Now don’t think that what I mean is anything boring or subdued, the Gáe Bolg are anything but, it is rather in the balance that MMR have struck with them. The Gáe Bolg have a rich sound that is thoroughly enjoyable and doesn’t push anything too far. The stage is large and airy, which is complimented with full sounding notes so that that stage is really nicely populated. With few instruments going on there is focus and detail, yet when the music builds up in complexity, the stage starts to fill up and creates a highly dynamic and enveloping musical experience. There is intimacy to it, while never feeling congested or harming separation and detail.

The bass is well controlled, but quite full sounding at the same time. It has weight to it and is perhaps not the fastest most articulate bass, but I think that is the point. It is tuned without going too far, so that it starts to build up a rich and relaxing signature that is still highly versatile. Mids have a hint of warmth and again that richness with clear vocals that are very nice. Not the best vocals, but good clarity and density nonetheless. Treble is smooth and a little bit laid back without harming sparkle or reducing the airiness too much. I won’t say it is entirely linear, but what it is, is balanced. By not pushing anything too much, the Gáe Bolg are tremendously versatile and enjoyable. I have listened to a lot of different music and they do it all very well. Mind you, I don’t think that these are the most accurate in terms of timbre and so with classical music you do start to notice it a little. Yet at the same time it never bothered me because it was so enjoyable.

The Gáe Bolg are like a high quality chocolate mouse that does not have the pretentiousness that comes with a Michelin Star. This is no plate left mostly empty with a tiny scoop in the middle and silly garnishing. This is proper pudding that avoids artificial flavouring because it is naturally rich. That makes the music so enjoyable. It is rich, but doesn’t sound “off”. In fact, it sounds just right. Let’s take a closer look at that…

As I have explained, I got new music from everywhere to try out and here is a selection of some of those albums that I think illustrate the sound of the Gáe Bolg very nicely.


Yeahman - Ostriconi
Just to illustrate how arbitrary my selection criteria were for albums, I picked Yeahman’s Ostriconi out of the new album releases of the Qobuz front page simply because the album art looked peaceful. Indeed the album is very relaxed and seems to have some world music influences that the DJ mixes with electronic. The album also shows how wonderful it is to just explore because I absolutely love this album. It is cheerful, feels positive and bright. Tell me you don’t cheer up when hearing Baixi Baixi.

The Gáe Bolg adapt to this incredibly well with their clarity and balance, where the bass is delicious and acoustic instruments sound fresh. The track Soupe Fue has a wonderful sparkle to it with a thick and lush bass line that always gets me moving in my seat. Imaging is once again great and it surprised me how far away some details of the track are (towards the end of the track on the left). Strings have a really nice crispness with just a hint of bite, but again in moderation, as you can hear in the track Sakoneta.

Minco Eggersman - Unifony
This one I happened to come across while looking at Dune Blue’s (a distributor I sometimes collaborate with) Facebook page. They were promoting the Final D8000 headphones together with Minco Eggersman’s second Unifony album and I happened to have Dune Blue’s demo unit of the D8000 over, so good enough excuse to have a listen.

This album has a very relaxed, sort of minimalist flow to it, not unlike Ludovico Einaudi. It is super relaxed and the Gáe Bolg render it really well. Imaging is excellent with great positional information and so the layers build up really well, as you can hear in the build up of the track Hunt. Because of the Gáe Bolg’s richness the pace feels slow, relaxed and enjoyable, which is complimented with a little bit of crisp clarity to for instance horns, strings and piano notes. The track Whisper shows off this contrast between the slower, heavier bass line and the crispness of the piano notes.

Porcupine Tree - In Absentia
Less arbitrary was the tip I got from my Twister6 colleague Anirudh (Animagus), who is a professional musician, producer and all-round music expert. He recommended I give the progressive rock band Porcupine Tree’s album In Absentia a go, as it is highly regarded for its production as well as the music itself. I am completely new to prog rock (as far as I am aware anyway), but this is another album that has quickly shot to the top of my favourites.

The track Trains shows off the Gáe Bolg’s very nice vocals as well as some excellent acoustic guitars sections that I think Gáe Bolg render really well. The solo sections get me air-guitaring along as if I have any idea on how to play the guitar. Under that layer of vocals and acoustic you get that meaty bass with pretty good impact from the kick drum. Talking about air-guitaring like an idiot, one of my favourite tracks is Wedding Nails, which the Gáe Bolg give a ton of energy, nice crunch on the electric guitars and a great image that feels hollow, like sound resonating in an abandoned building that is quite eery. Interestingly, I think Joseph Mou seems to have a talent for tuning for guitars. Those always sound great. I had that with the Jomo Trinity, the Thummim and now the Gáe Bolg. The opening of Blackest Eyes shows off the imaging and richness of the Gáe Bolg really well. Starting with a sound that feels like it is flying around your head with great panning action before it bursts into gear and you get this sense of the music enveloping you.

Goldfrapp - Felt Mountain / Black Cherry
My friends on Head-fi know I have a soft spot for female vocals and one of my friends recommended Goldfrapp. He suggested that I start with Felt Mountain, but I ended up listening to Black Cherry more. On Felt Mountain, which is a more conventional album, tracks like Paper Bag shows how wonderfully intimate and hauntingly beautiful the Gáe Bolg can render Allison Goldfrapp’s voice.

In the end I loved Black Cherry more because of its energetic vibe and great use of synths. There is lots going on in tracks like Crystalline Green, where the imaging of the Gáe Bolg works great in balancing intimacy with somehow still a great sense of spaciousness. My favourite track has to be Tiptoe, which I was listening to the first time while cooking dinner and it had me dancing through the kitchen. Here the Gáe Bolg have that balance with richness and crisp sounds layered, but always with easy-going, fun and punchy musicality.

Snarky Puppy - We Like It Here
Snarky Puppy is forever being plugged by my friend and reviewer for the Headphone List, Deezel. So after having heard him talk about it for so long, I had to give it a go. It is a type of instrumental jazz fusion and can get very layered, with lots going on.

In the opening track Shofukan, you get a sense of how the Gáe Bolg don’t push things too far. Horns in it sound great, but don’t have the bite you often get. I quite like that bite, but this smoother presentation is what makes the Gáe Bolg so wonderful for long listening. It still sounds exciting and yet never gets fatiguing. In Jambone things get feel quite hectic and it has lots going on, yet the Gáe Bolg allow you to hear every element without pushing separation. Again it is that moderation I feel the Gáe Bolg have that makes them so wonderfully easy going. It has a great guitar solo as well.

Max Richter - The Four Seasons (recomposed)
What about classical music? I think regular readers of my reviews know how much I love classical music. Here I find the Gáe Bolg less in their element, as critical clarity, separation and transparency are not quite there. The Gáe Bolg have nice clarity and such, but there is a soft edge around instruments that is not as suited to classical music if you are being critical. However, it is also exactly that softer edge that gives Gáe Bolg their charm and classical music is still very enjoyable to listen to. Because of this characteristic I actually found that Max Richter’s type of classical music works very well.

I know Vivaldi’s The Four Seasons very well, having included it in my series Masters of Classical Music for the Vision Ears VE5. Max Richter’s recomposition of it adds a modern twist that benefits from the richness of the Gáe Bolg, while violins still sound rather fruity on top of that richness. (I’m starting to get hungry from all the food analogies.)

To be honest, I actually don’t like this recomposition at all. And why the heck is there a fifth “Shadow” season? The Four Seasons, Max, just four. But irrespective of that, I do think the Gáe Bolg have the richness that works for this twist on classical music.

For comparisons I switched back to the stock cable for the Gáe Bolg and used the Violectric V380 desktop DAC/amp with my MacBook Pro as a source for streaming the different albums from Qobuz. The V380 comes with two single ended 6.3mm headphone outputs and thus makes it ideal for direct comparisons, with only minor adjustments in volume needed between IEMs.

-Campfire Audio Ara-
The Campfire Audio Ara are price right in the middle of the Lite and Complete versions of Gáe Bolg at US$1,299. In terms of build quality the two are very similar, although the designs are completely different. The Gáe Bolg come with a much more elaborate design in aluminium and a striking colour, where the Ara look more industrial by comparison with a bare titanium shell. I personally prefer the look of the Ara, as it has been one of my favourite designs ever since I first saw it with Campfire Audio’s similarly designed Andromeda. I can however see others preferring the more intricate design of the Gáe Bolg.

In terms of sound I find the Ara to have a more intimate presentation with a smaller stage, less air and more forward vocals by comparison. The Ara are also a bit brighter in the treble and have relatively more mid-bass presence. The Gáe Bolg have the larger, more airy stage and I feel perform beyond the Ara in terms of imaging and clarity. The bass is tighter, faster and more impactful, and while the treble is not as sparkly as that of the Ara, I find that Gáe Bolg still manage a more dynamic overall feel with nice energy in strings.

I think the Ara have perhaps the edge in build quality with the titanium instead of aluminium shells and a better stock cable, but the Gáe Bolg are in my opinion the better performers in terms of sound.


-Vision Ears VE5-
The Vision Ears VE5 are once again similar in price starting at €1,250 for the Signature Edition universal. In terms of build quality you get very different propositions with the VE5 being made out of resin and the Gáe Bolg out of metal. Obviously this makes the VE5 much lighter and Vision Ears offer them in CIEM and custom universal, so that the fit can be perfect and the design entirely the way you want it.

In terms of sound there is a big difference in presentation. The VE5 have a uniquely focused presentation that is more intimate, yet presents instruments with greater clarity, against a blacker background and with more air around them. They also have some of the very best vocals available. By comparison the Gáe Bolg feel bigger, more dynamic in their presentation, not quite as clean or focused, but more fun, even though I find them very nice for classical music as well. The Gáe Bolg are in my opinion the more versatile, whereas the VE5 are the more accurate sounding IEMs.

This comparison is more apples vs oranges and I think both have a lot going for them. For versatility the Gáe Bolg have it, where the VE5 offer less versatility in exchange for one of the most unique and beautiful presentations I know. If anything, these two are complementary.

-FiR Audio VxV-
The VxV came in just as I was finishing up this review and make for the most interesting comparison. The VxV are explicitly marketed as “EDC” and sit at a very attractive price of US$999 just under the Gáe Bolg. The VxV feel purposely designed as ‘carry everywhere’ IEMs with an excellent build quality that is similar to the Gáe Bolg, but more understated in their design. The VxV are smaller and lighter, and in terms of comfort I think both do really well. The VxV however have the advantage of the Atom pressure release module that is very effective combating fatigue. The stock cable of the VxV is also very nice, incredibly supple and of a higher quality than the stock cable of the Gáe Bolg.

In terms of sound this has been a really difficult comparison because these are very close and yet have a slightly different presentation. The Gáe Bolg feel more linear and balanced with a more spacious stage and perhaps more airiness. However, while the VxV have a more forward feel to them that gives a sense of intimacy, the Atom module still generates a spacious presentation and separation of instruments is outstanding, as well as imaging. The VxV feel a little warmer and even more dynamic than the Gáe Bolg and with better vocals, but don’t have the richness that makes the Gáe Bolg so nice. The bass is really tricky because both have a nice bass. The Gáe Bolg feel like there is more weight behind it, whereas the bass of the VxV has more texture and impact.

These two are incredibly close and it is hard to pick one over the other. I personally prefer the VxV, but listening to the Gáe Bolg never makes me feel like I want to switch. The choice here is really down to personal preferences and budget, but both are excellent performers.


Aftermarket cables

-Eletech Prudence 8-
I had initially planned to try out a number of different cables, but this review was already getting very long and so I decided to skip cable rolling, except for one. The Eletech Prudence 8-wire version because how could I not try out what the effect would be of doubling up on the fun supplied by the standard Prudence.

Doubling wires can have unpredictable effects and in this case I was a little surprised by the result, although pleasantly so. Prudence 8 pushes back the presentation a little to make it feel less intimate and not quite as rich due to a smaller note size and a little less warmth. In return Prudence 8 adds air and clarity with a tighter and more impactful bass and a bit more sparkle. To me it does not harm the musicality at all and it is a very enjoyable pairing. However, I don’t know if I might prefer the standard Prudence, I quite like the intimacy and the enveloping rich feel that Gáe Bolg provide with it.

If it was not clear yet, I love what MMR have done with the Gáe Bolg. From the build quality to the comfort and from the optional cable upgrade to the highly versatile and enjoyable sound, the Gáe Bolg offer a very complete package. The rich, yet balanced sound is never fatiguing and will work with every type of music. That is also why this review took me way too long to get written. Too much time spent enjoying the music [smug grin]. I can highly recommend a demo!
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Watermelon Boi

100+ Head-Fier
MMR Gae Bolg: A Rational Piercer
Pros: Marvelous design
Elegant, highly-refined sound signature
Great performer even within its price
Significantly more ergonomic than past models
Cons: Earpieces still may be big for some
MMR Gae Bolg Review: A Rational Piercer

If anybody asks what was the hottest new brand in 2020, I would say pick Metal Magic Research (MMR). Founded by the head of Jomo Audio, MMR is a Singaporean IEM brand that has been presenting unprecedentedly unique products along with their new cable brand, Eletech. MMR's first two releases, Homunculus and Thummim, were just enough to gain a significant amount of interest throughout multiple countries. I was also able to have a quick audition for these two special IEMs, I could tell their sounds being as gorgeous as much as their form factor.

One thing to note, however, is that MMR is a brand that mainly focuses on high-end premium products. Homunculus and Thummim are each priced at $1699 and $4499, which are no easy pricing for many audiophiles to invest in. However, now we have quite good news. MMR announced a new model just recently that is meant to lower the price barrier for us to experience the "metal magic" these IEMs ooze out - presenting MMR Gae Bolg. Gae Bolg is by far the most affordable option available from MMR with a price tag of $1199. Okay, $1199 sure may not sound so affordable, but such a price is no longer a surprise in the IEM market. Alongside, what really matters is how would this new IEM sound and see if this one has a justifiable performance for its price. It is now time for us to take a deeper look into Gae Bolg.

Packaging 3.jpg
Packaging 2.jpg

Just as their previous IEMs were done, the packaging of Gae Bolg has creative and mysterious artworks that make the unboxing experience enjoyable. The box is wider and thinner compared to the previous products with a black-red color them going on throughout the unboxing. Lining up with the theme of its naming, An artwork of the Gae Bolg spear is presented at the center of the outer lid. Other than the earpieces, the packaging includes a stock cable, 3 pairs of Acoustune AET07 eartips (S/M/L), a portable case, a cleaning tool, a carabiner, and a metal emblem card with a cut-out of the Gae Bolg logo. The carrying case has a red theme with a similar form factor to the one included in Homunculus. Although I do not have the case in my hands, they are made out of genuine cowhide and has a great build quality based on my experience with MMR's other leather cases.

Earpieces - The Form Factors

Gae Bolg's design is simply stunning. The looks on them would already explain for themselves. With a rounded teardrop shape, the earpieces use a fully-machined CNC aluminum. The faceplates have a deep red color with complicated yet beautiful Viking patterns. The inner side behind the red Viking cut-outs has a matte black finish, making Gae Bolg's faceplate design stand out even stronger. Thus, the visible metal grains from the red faceplate completes its gorgeous form factor.

The other side of the earpiece also has a similar but simpler patterning, preventing this inner side from appearing too plain. The nozzles are long enough to compensate for their rather large earpieces and the overall fit is quite comfortable. It is still a large size for those with smaller ears, though most users would not have a problem fitting these into the ears as the ergonomics are further advanced from Homunculus or Thummim.

Earpieces - The Specs and Gae Bolg Structures

Gae Bolg consists of 5 Balanced Armature drivers and involved with dedicated internal structures. First, Gae Bolg incorporates vented BA drivers as a number of other manufacturers have been doing - but on the lows, instead. Very interesting to find this because manufacturers usually apply ventings on the BA drivers that take charge of the upper-ends. Anyhow, Gae Bolg's driver setup is comprised of 2 vented lows, 1 mids, 1 vented mid-highs, and 1 tweeter. These drivers are infused all in one using a 4-Way passive EFD (Electro Frequency Division), efficiently handling the division of the sonic bands. Each driver is coupled with specific filters correspondingly to created the needed sound signature.

On top of that, MMR loaded Gae Bolg with a dedicated chamber named GBAC (GaeBolg's exclusive Acoustics Chamber) that finalizes the acoustic formation for these drivers. This is also similar to Campfire Audio's Solid-Body structure, but the execution from MMR was done more daringly. Gae Bolg uses a wider and longer chamber where it even has spiral-like waveguides within its inner structure. GBAC serves to correct the phasing differences between the BA drivers, yet done in a more natural manner Such phase-correcting method creates a sound that is significantly more organic than some old IEMs where the phases were corrected simply by cutting tubes in different lengths. Last but not least, Gae Bolg uses a TriBore Waveguide at the section of the inner chamber, allowing these multiple sound production to stay cleanly divided until they reach the tip of the nozzle.


Now, there is one exclusive option for Gae Bolg and it is that you could choose the cable option. The $1199 deal is called a Light packaging that includes a standard 2pin-3.5mm cable. Once you add $200 (therefore $1399) with your purchase, you could upgrade to a Complete packaging that includes Eletech Prudence SPC cable with a choice of cable termination (2.5mm/3.5mm/4.4mm). For your interest, Eletech Prudence is a premium cable that is also included with Homunculus. The regular stock cable from Gae Bolg is nothing unfamiliar to us - a light, smooth 4-braided cable with a black sleeving. While Eletech Prudence is recommended to bring out the full potential of Gae Bolg, the regular cable still does a very fine job of setting up a place for Gae Bolg to make its dance.

Sound impression - Lows

MMR created Gae Bolg as a full-BA IEM, though that never means Gae Bolg should have weak bass. Lows produce thick, masculine growlings with prominent texture details. The sound rays are meaty and thick in color, thoroughly filling up the lower ground of the headroom with vibrant yet controlled bass presence. The bass quantity weighs similar as slightly v-shaped (v instead of V) but with a low-end presence that is bold as any other bass-heavy IEMs. Clarifying the overall sound signature from the getgo, Gae Bolg shows a slightly w-shaped sound signature. Now continuing with the bass, the strikes are smooth in the exterior yet hard and dense in the interior. Such type of strikes allows a smooth listening experience while preserving the firmness and tightness of the bass.

Density-wise, Gae Bolg shows quite a meaty and tightened bass production - though what is interesting is that the low-end atmosphere does not get stuffy or feel to be getting "chocking" the upper-end. This is one of Gae Bolg's characteristics where it forms a vast and mildly openly bass. Such bass involves high density that unfolds evenly throughout the bass region, preventing the bass region from sounding like one large lump. Speaking of the bass region, I would like to point out another interesting element from Gae Bolg's low-end. First, the lows are well pulled down to the lower side of the staging that brings stability and weight. Second, while the lows are well lowered and calmed, both ends of the bass regions (L/R) continues to extend fuller and higher, forming a mild blooming. I found this to be a good way to keep the cleanliness of the bass while adding fullness.

Ultra lows are impressive for a full-BA setup. It possesses a deep, dark, and profound ambiance that makes stable dives. It also shows quite a bold presence in the music. The bass overall shows a gently warm temperature, yet its stuffiness-free atmosphere serves a bit as a refresher. To sum up, this high-quality bass forms a vast and large headroom while preventing them from losing density or tightness. This differs from those that have heavy and large bass but with tons of reverbs going on. If comparing a loose bass to a situation of forcing a thick chunk of bass into a wider region, Gae Bolg's low-end feels to be large to its nature that is accompanied with a good thickness. So lows are fully backing up the upper-end without easily bleeding into the lower mids. I would call that an "organized smoothness".


Sound impression - Mids

If I have to summarize how Gae Bolg sounds in the mids, I would state it as a "vigorous refinement". The tonality is much natural with an extremely steady presentation. Vocals flow with even emphases throughout the mid-range including the sibilance area. Perhaps Gae Bolg is one of the finest stability among IEMs I have tried until now. Technically, this was possible thanks to MMR's new GBAC chamber, a central system that corrects the phasing. Perceivably, it comes to be possible due to a particular characteristic of Gae Bolg's headroom - to have the center region of the bass lowered/leveled while each end of the bass region begins blooming. Perceivably, mids sit right on top and at the center of this bass region. As result, mid-layers are cleanly yet naturally sorted from the lows, forming a beautiful harmony between the two bands.

If you have experienced MMR/Eletech products, you may have noticed that these products pay attention to delivering fine grains or textures. There is no exception for Gae Bolg either. Gae Bolg most definitely does not have that water-soaked dullness nor dry and crumbly texture. It hits a sweet spot of containing moderate moisture to the sound while being quite blatant in revealing the textures with good crispness. On top of that, mids show highly stabled phasing and emphases, heading towards a reference-like sound signature that has plenty of musicality. Vocals are only mildly thicker from neutral, which is still very neutral. Instead, it adds body and fullness to the vocals. Plus, mids also show an appropriate amount of 3D spetialness, which makes vocals sound even lively.

Both male and female vocals work just as nice with Gae Bolg. Since this IEM shows rather consistent yet noticeable changes depending on different eartips, it has a good nature that is easy to play around with tip-rolling. Just like the lows did, mids also show a mild openness to its atmosphere - but now topped with a mild airiness. Sibilances are barely present throughout many tracks and genres - though if they do, they get nowhere near feeling piercing or fatiguing. They rather behave calmly and with a small volume, ending up to be adding extra crispiness to the music.


Sound impression - Highs, etc.

Highs show a clear and distinct tone along with the crispy bites. With a mildly lesser quantity, highs stand in the same position (or only half of a step behind) as mids. However, their presence within the music is just as strong as lows or mids. The treble strikes are refreshing, airy, and super clean. It has a cooling tone to it which serves as a refresher to compensate for the warmness from the low-mids. These appropriately contrasted temperatures serve Gae Bolg to bring out a wider color spectrum from the music, as well as making the music sound more drastic. The texture, as I have been mentioning all along with this review, busts out the most here in the trebles. It is high in density, even finer in texture particles, and presents nothing but cleanliness. It is a manifest type of treble that does not allow any dull, ambiguous environment to be formed.

These trebles are accurate and backed up with power. Paying attention to these clear treble notes brings pleasure to me on their own. Also, while I have mentioned these trebles to have a manifest attitude, that does not mean they exclude the natural treble reverbs. Removing them would degrade the liveliness, so the reverbs are surely preserved with good clarity. The treble tone is much neutral, yet its unique texture exposure and fineness makes them sound addictive to a wonder. Gae Bolg has a treble that is very much fatigue-free which is also capable of showing blatantly clear resolution. For Gae Bolg, highs are not decorative elements that are simply there to serve the lower-ends - but to perform strongly on their own to create an equal amount of charms. As mentioned a bit from the lows, the sound stage and headroom are large, full, and grand. What is special about Gae Bolg's headroom is not just about the size. It is because this largeness is executed in a very gentle way that never exaggerates the music. The separation is also on-point, showing great accuracy while staying harmonious.


Comparisons - Against Campfire Audio Andromeda 2020 (5BA)

This is an interesting comparison since both Gae Bolg and Andromeda 2020 use 5 Balanced Armatures as well as built-in waveguides for creating an accurate, harmonious sound. While they are similar in terms of sound signature since both draw a w-shaped sound, though they are in fact quite different as we dig into the details. First off, the overall sound is more closely presented on the Andromeda. Such "closeness" of the sound could be altered depending on different eartips, though under the circumstance of using the same eartip, Andromeda 2020 is noticeably more up-close and personal.

Though when it comes to the headroom size, Gae Bolg definitely takes the lead. Plus, Gae Bolg is also capable of approaching close to the ears - it is just that it forms a longer and deeper width. Unless you are a user that specifically prefers a moderately-sized headroom that focuses more on presenting a close, exquisite sound, Gae Bolg surely takes the lead in headroom as it is more grand and fuller. The Andromeda 2020 may be coming relatively short in headroom, it has its own unique charm which is the beautifully articulated upper ends. These upper ends that Campfire Audio has crafted were the major reason why Andromeda was so popular, which are now even better in Andromeda 2020.

Another key difference is the bass. Andromeda 2020 also brings out more of a typical (which is not inherently had) BA characteristic where the bass is solid as a rock. The bass reverbs are only mildly lesser and feels to have a faster speed, hence the faster strike and decay. Gae Bolg takes a more organic and neutral approach in the bass texture, still showing thorough agileness but smoother and creamier than Andromeda 2020. Lastly, and which is the most noticeable difference, the background. Andromeda 2020 has a brighter background that has a cheerful nature whereas Gae Bolg has a darker background, showing a dim and quiet nature. Because of this, Andromeda 2020 matches better for lively or exciting tracks while Gae Bolg shows superiority in tracks that benefit elegance, calmness, or seriousness.

Comparisons - Against Moondrop Solis (2EST+4BA)

While I was not expecting to be so, these two are interestingly similar. But of course, they still have distinguishable differences. The basis of their sound signatures is heading in the same direction - to be highly musical and balanced at the same time, showing a bold w-shaped sound. Also, the difference in their physical sizes impacts their style of presenting the sound stage. Although not by a huge margin, Gae Bolg fills the music a bit wider (sideways) while Solis does a bit better job pulling out the vertical largeness (or the ups and downs). Alongside, Solis tends to present the music in a mildly more compact headroom with further thickened density. Gae Bolg, on the other hand, places wider spacing between the sounds, letting the "emptiness" to play its role in the music.

To talk about textures, Gae Bolg brings out refined textures with much smoothness. Although Solis' texture reaches nearly as refined as Gae Bolg's, the texture from Solis feels to have this thin, sleek layer of coating on top of the sound. This allows the texture to feel just as smooth (or even smoother) while revealing texture details as good as Gae Bolg. Overall, both IEMs show an equal level of performance of charms which all comes down to personal preferences. After the comparison between these two, I am impressed by both sides - Gae Bolg for its treble performance that matches up high as Solis, and Solis for its headroom that stretches nearly as large as Gae Bolg's.


Gae Bolg is an easier gateway for users to experience the captivating sound that MMR products provide. The aesthetics first catch your eyes as you encounter it, then the sound catches your attention. The price tag may have gone through a diet, Gae Bolg still follows the exact same "MMR DNA" that was apparent from its big brothers; Homunculus and Thummim. If you ask the specifics of what that MMR DNA consists of, I would point out elegance and fineness. Despite my quick encounter with the upper two models, these two elements were strongly apparent from their sound, which I was once again able to hear through Gae Bolg. Most importantly, at a lower price. For those looking for a virtuous-sounding flagship IEM, or those who were impressed by MMR but was facing a higher price barrier, Gae Bolg would likely be a guaranteed performer that is more than good to pull the trigger.

Thanks to Metal Magic Research for providing Gae Bolg in exchange for an honest impression/feedback.
I am not affiliated with Metal Magic Research and none of my words were modded or asked to be changed.


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