MMR Gae 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.


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 favorable review.

e 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 ‘Every Day 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 finalizing 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 aluminum and takes inspiration from the mythical spear after which the Gáe Bolg were named. The beautiful satin red color 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 aluminum and designed with optimized 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.

mmr-gae_bolg-IMAGE_05Images 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.

e 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.

Page 2 – Source, and Presentation.
Page 3 – Comparisons, Aftermarket cables, and Conclusions.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s