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Westone Audio Mach 40 IEMs – The Golden Age BA Party

Westone Audio Mach 40 IEMs – The Golden Age BA Party

Westone Mach 40 is a 600 USD IEM or In-Ear Monitor, in the truthful sense of the word, being designed for actors, singers and musicians, having superior passive noise isolation from what you typically see out there, and a totally unique design. They will be compared to other upper midrange / high end IEMs, including IMR Acoustics PRO Dark Matter (900 USD), Oriveti OV800 (999 USD), Dethonray Tender 1 Planar IEMs (639 USD) and Campfire Holocene (650 USD). 



Westone is a huge name in the audio industry, being the pioneer of the in-ear monitor concept, asd they make some of the most widely used universal in-ear monitors, especially universal ones. They have a totally different approach to music, and most of their products are monitors, in the true sense of the word. This being said, audiophiles have taken a liking to this flat, precise sound, and as time went on, Westone became one of the most popular brands for audiophiles and music lovers from all over the world. It is important to note that Westone has focused on refining the balanced armature technology, so the results are usually quite intriguing. 

It should be noted that I have absolutely no affiliation with Westone, I am not receiving any incentive for this review or to sweeten things out. I’d like to thank Westone for providing the sample for this review. Every opinion expressed is mine and I stand by it. The purpose of this review is to help those interested in Westone Mach 40 IEMs find their next music companion. 


Product Link

You can grab one from www.amazon.com here: https://amzn.to/3DVtFVP

If you’re in the UK, you can grab one from www.amazon.co.uk here: https://amzn.to/3Sj2ubN

And if you’re from Europe, you can grab one from www.amazon.de here: https://amzn.to/3dLWNE7


Build Quality/Aesthetics/Fit/Comfort

Starting with the build quality and design of Mach 40, this is an incredibly light IEM, with one of the lightest designs I’ve seen in years. It is also incredibly small, with a super ergonomic design, made to fit every ear shape and type out there, making it an instant favorite for most music lovers. The info you need to know though, is that they have a super deep fit with an extremely narrow tube, so tip rolling is essential. For example, I am currently finding the best comfort with shorter tips, smaller size, to achieve the perfect fit and it will most certainly be different for you. There is some void, which is a word I haven’t had to write in a long time. This is because Mach 40 is a pure BA or balanced armature driver IEM and does not have ventilation nor does it need any ventilation. If you find the void to be uncomfortable, using foam tips solves the issue entirely, and provides better passive noise isolation, and better comfort. Basically, Westone IEMs were designed to be used with foam tips. 

Proceeding to more esoteric information, Mach 40 has a 3-way Passive Crossover, and it relies on Four (4) Balanced Armature Drivers to deliver sound for Mach 40. They have a quoted Frequency response of 10 Hz all the way to 20 kHz, and they have a quoted sensitivity of 100 dB at 1kHz, which is about fair for what I hear, as they are somewhat hard to drive and not overly sensitive, especially for such diminutive looking IEMs. The higher impedance of 30 OHMs (relative to other IEMs in the price range), means that you won’t ever hear hissing or background noise from sources. 

The drivers are configured for two drivers powering the bottom end of the sound (bass), one driver powering the midrange, and one driver powering the treble. Westone has their own SUPERBaX cable, which is a different cable than what we see with most IEMs, it has a good quality, but it is extremely thin. I can’t test it against other cables or do cable rolling as Westone uses T2 connectors, for which I don’t currently have any aftermarket cables. Westone also includes a rich accessory setup with Mach 40, with a dustproof case from Pelican, and a huge selection of tips, both storage and transport solutions for Mach 40. 

The passive noise isolation is insanely high, and you can barely hear even loud music or loud noise around while wearing Mach 40. It is between 25 and 35 dB of passive noise isolation, even quiet music will drown out typing, voices or even other music. All in all, Westone IEMS in general, and Mach 40 are a unique experience you need to experience to fully understand how comfortable IEMs can be, when a deep fit is done properly. 


Sound Quality

Since we have just 4 Balanced Armature, you might have certain expectations and not in a good way, but you’d be gravely mistaken if you thought you absolutely need 24 Balanced Armatures like Ambient Acoustics MAD24 has. Instead, you just need really good BA Drivers, and some careful planning to get an interesting sound. For today’s review I’ve been using a collection of sources, including iBasso DX170, Tempotec V6, Lotto PAW S2, Aune X1s GT, iFi Audio Hip-Dac2, and Astell&Kern A&Ultima SP2000T. All of those sources can drive Mach 40 properly, and they don’t scale much with source, so you should have a pretty similar experience to what I describe here today, regardless of what your source will be. 

While with most IEMs, you can get a decent sound without too much fiddling, for Mach 40 it is essential to have the best seal and isolation possible. They will sound extremely flat and lifeless, also will roll off at both sonic ends (bass and treble) if the seal is not proper. The best wat to be sure you’re hearing their max is to use larger than you need tips, especially foam and scale down from there. I have experimented a lot and went from rubber green to either using foam blue or rubber blue eventually. The absolutely best sound for my ears has been with rubber colorless tips, the ones that offer the shallowest fit and which feel the most like traditional IEMs. They have lower passive noise isolation, but a much more natural presentation. Quite ironic, while writing this very paragraph, I switched to rubber blue one last time. Those have the absolutely best fit, seal and ergonomics for me, offering what I can call the true Westone Mach 40 sound. With most IEMs, I fiddle very little as I get a super good seal immediately, but Westone Mach 40 has such a narrow sonic tube / nozzle that most tips could end up being much smaller than small tip size for other IEMs. This means that Mach 40 will be more comfortable than most IEMs out there, but you will need to experiment more with tip rolling and to get a proper seal. So, the winner is the Rubber Blue, offering a focused, but clean and clear sound. Also, while I loved the colorless rubber tips sonically, they don’t sit well and slide out of my ears after a while. 

Now, in the configuration I feel I’m having proper seal, Westone Mach 40 sounds extremely clean, clear and has a good amount of bass and a fair treble extension. I heard a much stronger treble presence and impact with the shorter rubber green tips, but those aren’t exactly what I need personally, as they don’t hold their fit for long periods of time. At any rate, the signature of Westone Mach 40 is a midrange-forward, clean and detailed one, with super detailing and precision, a quick bass, quick midrange and quick treble. Everything is fast, edging on being a bit dry, but also having pinpoint precision. Everything Etymotic was supposed to offer is offered by Mach 40, but more musically, with a more fluid texture, much better resolution, and better comfort for sure. 

The bass of Mach 40 is incredibly fast, and accurate. It has a neutral quantity and feels linear with any of the tips you might be using. If you’re a basshead, there are other options, Mach 40 is made to be a monitor and show bass only where it is absolutely present in the track / mix. To me, it feels like Mach 40 is the ideal voice and guitar / instrument monitor, but it is not made to monitor and mix drums in particular, as the midrange is surely the central element of their sound. The bass of Mach 40 is focused but has good nuance when the song has a nuanced bass and a strong bottom end. For example, you don’t hear a lot of lows with most Grindcore music, but Mach 40 is fully able to power your head with lows if you’re listening to some Lunecell and other Psy Trance pieces. There’s no coloration in the bass, it is purely neutral, and it has no sway to warmer or colder, simply linear and precise. For example, with metal I could not hear much bass with most songs, except for some metallica tracks, but with LuneCell – Tetrapod, at half of the song and after, my head started vibing with the bass line Mach 40 delivers. 

Speaking of which, the midrange is also extremely linear, and Mach 40 has the most precise midrange I’ve heard in a long while. The overall resolution is outstanding, to say the least. Even super top of the line IEMs don’t always have the precision and resolution Mach 40 has, but what you typically expect from a really resolute IEM is dryness and fatigue, but Westone somehow designed Mach 40 to not be fatiguing. Instead of having a stronger lower midrange or upper midrange, the midrange of Mach 40 is super linear, clean and well layered. Although the soundstage is natural in size, they have good instrument separation and stereo imaging, creating a very coherent and naturally sized / placed 3D image of the song in your head. Another thing you will notice once you start playing music through Mach 40 is that you will absolutely fall in love with the vocal presentation, especially female voices, pianos and violins. Despite the tonality being dead flat and linear, you will love how Mach 40 is able to offer a natural texture to female voices and guitars, to offer a tactile feeling for pianos and a deep, emotional presentation for Violins. While I haven’t had this feeling in a long period of time, the smaller soundstage, combined with the resolution of Mach 40 made me turn around a few times while listening to certain tracks, even rap tracks, because I could hear some background information that I typically don’t notice. I’m talking especially about backing vocals and background voice tracks that most IEMs simply don’t reveal as well. Don’t get me wrong, all IEMs will show those bits of information above a certain price point, but if we’re talking voices, Mach 40 surely makes it obvious. One music style I LOVE with Mach 40 is rap and hip-hop, and I didn’t expect this, but they keep up with huge bass lines in rap, and also make voices pleasing, both male and female voices in rap. You can quickly test this by opening up any ERB track.

The treble of Mach 40 is clean, well extended but fatigue-free, and once again, very linear. This means no uplift, no brightness, no lower treble extra energy, but a simple, clean and smooth treble that won’t leave you gasping for air. All in all, the whole signature is super linear, precise and the midrange will make you fall in love with it. It made me realize how much I can love pop and songs heavily relying on voices, especially female voices. YFU Baby in particular has a sweet and lush presentation through Mach 40, if you’re curious what’s the kind of music I’ve been enjoying on those bad boys. 



Westone Audio Mach 40 vs Oriveti OV800 (600 USD vs 999 USD) – We start with the package which feels more solid on Mach 40. The comfort is also slightly better on Mach 40, which feels lighter, and has a smaller tube design, offering easier fitting for people with narrow ear tubes. The sound is actually similar to the comparisons above, as OV800 has a brighter presentation, with more upper midrange and lower treble, more energy in the highs, better instrument separation, and a wider soundstage. Mach 40 sounds more natural, has a better sub bass extension and presence, when the song asks for it. The midrange in particular is sweeter and cleaner on Mach 40, which I prefer for Pop, Rock and Rap, while I prefer OV800 for Rock, Metal and EMD. 

Westone Audio Mach 40 vs Dethonray Tender 1 (600 USD vs 639 USD) – We have a richer package for Mach 40, with a transport case, and a higher selection of tips. Tender 1 is super comfy, but Mach 40 has a deeper fit, and once you get a good seal, they’ll be more comfortable than Tender 1. The overall sound is much brighter on Tender 1, with lower bass quantity, and a richer upper midrange / lower treble. Mach 40 sounds flatter, more linear, darker, but also less fatiguing and more even. The vocal presentation is more natural on Mach 40, which sounds more even, while Tender 1 presents cymbals and rock / metal music with more energy and has a better soundstage, with more width and better instrument separation. 

Westone Audio Mach 40 vs IMR Acoustics PRO Dark Matter (600 USD vs 900 USD) – We start with a strong comparison, as IMR Dark Matter has a stronger package than Mach 40, coming with 3 cables in the package, also with tuning option, and a leather transport case. The overall comfort is similar, but Mach 40 offers more passive noise isolation, by about 5dB, once you get a good fit. The sonic presentation changes a lot for Dark Matter, but in the most V-Shaped presentation, or the least damped one, Dark Matter has a stronger sub bass, stronger bass, a thicker and a warmer sound, and a stronger, brighter more open treble. This also leads to more impact and a wider soundstage. By comparison, Mach 40 wins heavily if you’re looking for a precise and clean voicing, as it has a more even and precise tonality for voices, a faster and more precise bass, also a less fatiguing and smoother treble. I can keep Mach 40 in my ears for many many hours on a row, while Dark Matter can get a bit much after 3-4 hours. 

Westone Audio Mach 40 vs Campfire Holocene (600 USD vs 650 USD) – The overall package is more impressive on Mach 40, which comes with more tips, a better transport case, and is kept more safely during shipping. The comfort is different, Holocene has a shallower fit, and requires less fiddling, while Mach 40 can be better at passive noise isolation, but also requires more tip rolling and will result in a multitude of sonic presentations (depending on the depth and seal level the tips you’re currently using offer). The main signature is much brighter, more open and wider on the Holocene, but the raw resolution and detail is higher on Mach 40. Also, Mach 40 brings the voices much closer to the listener, with better impact at the voice level, has more abss, a deeper bass, and keeps more honest to the track, being less colored in tuning than Holocene, which has a very specific signature that will apply to most tracks. The passive noise isolation is pretty much the same on both, as long as you have a good fit and seal. I prefer the Holocene for rock and metal, but Mach 40 works better for rap, pop, Trance, Psy music, and EMD too. 


Value and Conclusion

When you see the asking price of 600 USD for the Mach 40, and you even see them going on sale on their website and amazon sometimes, you don’t imagine they have such great price / performance ratio, and when you see that they actually deliver on all promises, you really are left wondering how comes they’re not more popular. Well, they’re a professional tool, the kind you see a guitarist or singer purchasing once and then using for many years, so while they don’t get spoken about as much as flavor of the month Chifi IEMs, or other audiophile products, Westone IEMs and Mach 40 has outstanding value and should age like fine wine. 

Even better, they have comfort, good sonic resolution, a flat and clean sound, and at the end of the day, if you’re looking for a high end IEM to match your recording process, or to accompany you on stage, or if you just want an earphone to deliver music to you in the purest manner possible, if you live a flat and clean midrange with a neutral-flat bass and treble, and a non-fatiguing but technically rich sound, Westone Mach 40 is a great option you should keep your eyes on, and a fully recommend IEM today. 


Product Link

You can grab one from www.amazon.com here: https://amzn.to/3DVtFVP

If you’re in the UK, you can grab one from www.amazon.co.uk here: https://amzn.to/3Sj2ubN

And if you’re from Europe, you can grab one from www.amazon.de here: https://amzn.to/3dLWNE7


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Full Playlist used for this review

We listened to more songs than those named in this playlist, but those are excellent for identifying a sonic signature.  I recommend trying most of the songs from this playlist, especially if you’re searching for new music! The playlists are different for Spotify, Tidal and Youtube, and based on the songs I enjoy and are available on each!




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  3. Flower Of Pain
    Flower Of Pain

    Thank you so much for the excellent review! I ordered a pair, hope they’ll be good on stage!

  4. Jack M

    Super nice review and excellent shots! I got my pair last week thanks to your recommendation, keep rocking on!

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