MMR – Gae Bolg Review

MMR Gae Bolg

In this article we look at the universal MMR Gae Bolg IEM, which is selling for $1,199.


Disclaimer: The MMR Gae Bolg was sent to us directly by MMR in exchange for our honest opinion in this review. The Gae Bolg doesn’t need to be returned to the factory after this review.


Metal Magic Research (MMR from now on in this article) is an IEM company in Singapore, lead by Joseph Mou which we of course all know from Jomo Audio. Jomo Audio has launched some great IEMs over the year, but with MMR the goal is to innovate. MMR strives to perfect the consummation of impeccable acoustics design with excellent aesthetics & ergonomics through the use of various ingenious methods to process manufacturing implementation.

“At MMR, we value ourselves at innovation excellence, superior customer experience and unsurpassed value preposition. Our products are meticulously designed to offer unsurpassed product serviceability and a unique portrayal of realism sound that adheres to our core principles of musical enjoyment. In doing so, we hope to foster a closely knitted community of music enthusiasts through our products and service”.

Up to now MMR has already launched two different IEM models: the Homunculus and the Thummim, who both had very outspoken and special designs. Unfortunately we didn’t get to review these on Headfonia yet, but who knows it might happen some day. According to MMR their universal IEMs are enclosed within luxury ultra precision CNC milled titanium shells offering perfect ergonomics, robust and allows for calculated acoustic reverberations. MMR products utilize cutting edge technology and unconventional acoustic chambers to produce IEMs with stellar performance.

MMR Gae Bolg

In this review we will be looking at the brand new Gae Bolg IEM, which was announced only yesterday. We’ve had it here for a couple of weeks already, so let’s have a closer look at the new and third model of MMR’s product line-up.

Gae Bolg

The universal Gae Bolg IEM is part of MMR’s new “Metal Series” and it is their first foray into entry-mid tier offerings amid their luxurious line-up. Looking at the market, the Gae Bolg is situated at the higher end part of mid-fi or even the high-fi part.

According to MMR, the Gae Bolg is reworked from the ground up with completely new ergonomics and a full BA-driver setup, bringing a harmonious balance in aesthetics and tonality. For Gae Bolg, MMR took the technology from their flagship IEM and deployed it in a pure BA setup with a new generation of shell and aesthetic design.

As you can read on MMR’s website, Gae Bolg is inspired by Irish mythological weaponry (see design). The Gae Bolg with the stock cable will sell for $1,199USD. The upgraded version, which has an Eletech Prudence cable, will be available for $1,399USD.

MMR Gae Bolg

Technical Specifications

Gae Bolg is a closed, universal 5 BA-driven universal IEM, engineered with linear acoustics in mind. It features an advanced 4-way passive electro-frequency division system (MMR -4-way EFD) that is infused with passive electronic components. MMR in the Gae Bolg also uses their Acoustic Chamber (GBAC) which is the central system behind its tuning and performance.


If you’re interested in more detail on the tech inside the Gae Bolg , you can find out all about it on MMR’s website right here. In short:

  • 5 BA drivers (1 tweeter, 1 vented Mid-High, 1 mid, 2 vented Lows)
  • 4-Way EFD
  • GB Acoustic Chamber
  • Tribore Waveguide
  • FR: 20Hz – 40kHz
  • Impedance: 25Ohm
  • Noise Isolation: -18dB

MMR Gae Bolg

Box & Accessories

This part is going to be short and easy. As this product is brand new it came delivered in a typical and well-known metal carrying case. On the inside we only found the IEM, one set of tips and a stock, single ended cable. Each ear piece was carefully packed in a tiny bubble wrap bag. Really cute.

The full packaging was supposed to arrive later, but I guess they couldn’t make it happen on time. So for the moment we can only show you the pictures we received last Monday. What a fancy packaging and presentation!


With the Gae Bolg, MMR was seeking to develop a timeless design with a complete profile that will excite most audiophiles. The design was inspired by Irish mythological weaponry.

Compared to MMR’s previous models, the Gae Bolg was completely reworked with a different team of designers, resulting in a complete overhaul of prior ergonomics and design language. The Gae Bolg is built with a fully aluminium shell and it according to MMR is lightweight (7gr per ear piece) and ergonomically pleasant while being robust in built.

Gae Bolg’s CNC’d face plate, according to MMR, as said pays homage to the Irish GaeBulg with a weaponry theme. The plate holds a lot of fine details and it sits above a matte black plate to highlight the patterns. The plate has a sand blasted finish to achieve a rugged, satin like texture. It’s perfectly executed.

MMR Gae Bolg

But why stop at the face plate, right? MMR took it a step further and they have also “decorated” the inner side of the chassis. As you can see in the pictures the chassis had a gunmetal color scheme, round edges and a smooth finish. The back plate is slightly raised and it features a rune design.

When I showed the Headfonia team the Gae Bolg’s design, I have to admit that the opinions were rather mixed. The majority didn’t feel any affection with the design, which actually quite surprised me as I think it looks stunning myself. Especially the face plate. To me it looks very nice, refreshing and new. It’s something different, something that catches your attention. The face plate’s amount of detail is astonishing and it’s a perfect way to display the high level workmanship of the MMR team.

I really love the unique design of the Gae Bolg’s front but it’s also nice to see that MMR has done something special with the back plate design. Personally I feel the Rune design is quite nice though the real magic is on the front of the unit. What do you think of the Gae Bolg’s design? Let us know in the comments!

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4.2/5 - (89 votes)

Lieven is living in Europe and he's the leader of the gang. He's running Headfonia as a side project next to his full time day job in Digital Marketing & Consultancy. He's a big fan of tube amps and custom inear monitors and has published hundreds of product reviews over the years.

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