Fit and Comfort

Seen above is the right channel of three members of the Westone MACH Series of IEMs that are individually placed into an artificial ear mold with the pre-installed shorter length size M silicone ear tip used. I have average-sized ears, and the ear mold above represents my own experiences well enough as a proxy. Size M silicone tips are my go-to for testing, since foam tips are not included by some brands. The actual shells of these IEMs are functionally similar for this section so the reason for the three photos here is to mostly show how the three cables work out in practice. The Linum BaX is the thinner of the lot and does not have pre-formed ear hooks or memory wire to where you have to effectively shove that thin cable behind the ear and hope the cable cinch helps hold it in place—it often does not! This alone can be a reason to go with one of the more expensive IEMs that gives you a less frustrating cable in the form of the Linum SuperBaX or UltraBaX as seen on the previous pages, and these also help provide additional support to the IEMs. I do wish Westone had gone with angled housings on the cable to allow for a more natural positioning behind the ears though. On the other hand, the IEMs themselves are easily among the most comfortable earphones I have ever used and this includes CIEMs molded to my ears. Westone is leveraging its decades of experience here in producing a tested design which fits sideways to fit most users and there is some wiggle room too. Those with narrower ears may still want to test this first but overall I'll give Westone the benefit of the doubt when it comes to securing a comfortable and isolating fit with these UIEMs. The all-plastic build also helps keep things light and they seem sturdy enough to handle daily wear and tear too.

Audio Performance

Audio Hardware

Westone continues to use only balanced armature drivers in its MACH Series of IEMs, and they happen to be custom drivers at that. This part will be fairly simple since the product name helps understand the number of drivers inside. For example, the MACH 10 has a single BA driver, the MACH 50 has five, and the MACH 80 has eight BA drivers. The eight different driver configurations result also in how they are working in terms of being responsible for the frequency range of interest from 20 Hz to 20 kHz. With the MACH 10, for example, things are again simple since we have a full-range driver handling everything. The other IEMs have crossovers involved as seen below:

• MACH 20: single low, single mid-high in a 2-way crossover
• MACH 30: single each low, mid, and high in a 3-way passive crossover
• MACH 40: dual lows, single mid, and single high in a 3-way passive crossover
• MACH 50: single low, dual mid, and dual highs in a 3-way passive crossover
• MACH 60: dual lows, dual mids, and dual highs in a 3-way passive crossover
• MACH 70: single low, dual mids, and quad highs in a 3-way passive crossover
• MACH 80: dual low, dual mids, and quad highs in a 3-way passive crossover

Westone rates the frequency response from 20 Hz to 18 kHz for the MACH 10/20/30 which is perhaps a driver limitation—not really a concern for the vast majority of users, and even less an issue for stage monitoring—provided it's actually extending that far, more on this soon. The others get the full 20 Hz to 20 kHz rating with the MACH 50 onward going beyond too. Another thing to note is all eight have much higher rated impedances (at 1 kHz anyway) compared to any other IEMs I've tested. This seems to be in trend with earphones and headphones made for the pro music market wherein you can benefit from a higher signal-to-noise ratio, and ultimately allows the output impedance of your source to be less of a worry too given music interfaces may not boast the ultra-low values we see on the consumer side of things these days. They are still quite easy to drive though owing to the fairly typical sensitivity values, so that also means a stage technician does not have to worry about a performer strapping on a bulky device for any of these IEMs.

Frequency Measurement and Listening

I will mention that I have a general preference for a warm-neutral signature with a slightly elevated bass, smooth treble range, detailed mids, and good tonal separation. I also generally prefer instrumental music over vocals, with favored genres including jazz and classical music.


Our reproducible testing methodology begins with a calibrated IEC711 audio coupler/artificial ear that IEMs can feed into enough for decent isolation. The audio coupler feeds into a USB sound card, which in turn goes to a laptop that has ARTA and REW running and the earphones connected to the laptop through a capable and transparent DAC/amp—I used the Periodic Audio Rhodium in addition to the Questyle M15 for my listening and measurements I begin with an impulse measurement to test for signal fidelity, calibrate the sound card and channel output, account for floor noise, and finally test the frequency response of each channel separately. Octave smoothing is at the 1/12th setting, which nets a good balance of detail and noise not being identified as useful data. Also, the default tuning was used for testing, and no app-based settings were chosen unless specifically mentioned. Each sample of interest is tested thrice with separate mounts to account for any fit issues, and an average is taken of the three individual measurements for statistical accuracy. For IEMs, I am also using the appropriate ear mold fitted to the audio coupler for a separate test to compare how the IEMs fare when installed in a pinna geometry instead of just the audio coupler. The raw data is then exported from REW and plotted in OriginPro for easier comparison.


The IEC711 is such that you can't really compare these results with most other test setups, especially those using a head and torso simulator (HATS). The raw dB numbers are also quite contingent on the set volume, gain levels, and sensitivity of the system. What is more useful information is how the left and right channels work across the rated frequency response in the various Westone MACH Series IEMs. This is all the more crucial for stage performers and mixing engineers so a good channel balance is key. I have measured both channels of all eight IEMs here but, in the interest of time and space, have decided to choose two random sets to show here. As we can see, both have good channel matching across the entire range noting that the coupler isn't the most reliable at the ultra-low and higher frequencies to begin with. In practice I had zero issues with any of the eight randomly chosen sets here, so Westone gets full points in this metric. Measurements taken after 100+ hours of testing, which included these playing a mix of various songs as well as white or pink noise and sine sweeps, showed no difference. There was no perceived burn-in effect thus, and none was measurable, either. The response with the anthropomorphic pinna in place matched the ideal scenario in the coupler quite well too and this is an indicator of how good the seal was when installed in the artificial ear.


Given this is an overview article, I will be mostly talking about how the various entries compare against each other in addition to how I liked them, if at all. As such, we'll have three different sets of comparisons here so as to not have all eight IEMs on the same crowded graph. First up, we have the average frequency response for both channels of the Westone MACH 10, 20, and 30 plotted against my personal target taken from VSG.squig.link, which also gives you an idea of my personal preferences to better correlate any possible biases. The tuning of a set of headphones or earphones does not have to match my target as long as it is tuned with some direction, makes sense, and is executed well. Note that all three sets are rated for "only" up to 18 kHz and that in itself would not have been an issue, but in practice there isn't a lot of treble energy past ~9-10 kHz outside of some air from 12-16 kHz. As such, I didn't think either of these three would be particularly great for orchestral music, especially if you cater to harps, cymbals, triangles etc. This one is otherwise quite simple to pick with the MACH 10 taking the win for me. It's the most neutral set of the trio and has the least mid-forward presence too. The MACH 20 and 30 sounded wrong to me with vocals sounding honky and overly forward-facing at the expense of instruments. The single driver without any crossover might be helping here whereas the passive crossover in the other two could be better implemented. All three felt equally resolving too, and I'll again give the win to the MACH 10 for imaging although neither three are really benchmarks in that regard. Given that on-stage performers typically listen for simpler audio cues and metronomes, having the most resolving IEMs isn't very critical. I also understand many prefer to have less ear gain for this application, although don't take this as gospel. As such, the MACH 10 should suffice for this use case anyway.


Next up we have the MACH 30 again for some common ground before giving way to the MACH 40/50/60. While the first round was won by the least expensive option, things are different here with the MACH 30 being my least favorite here. It isn't balanced at all and comes off warm to a fault before the mid-treble pierces your ears. If you have the budget, I'd highly recommend saving your cash and going with the MACH 10 or spending more and going with the MACH 40 which is significantly better in pretty much all regards. It's more resolving, has a more balanced tuning, and even provides enough depth to instrument harmonics to be the first proper monitoring-capable set of the MACH Series. The MACH 50 and 60 go further down this road by helping improve imaging, and perhaps this has to do with the better-executed ear gain too. The MACH 60 is the overall winner here and one of the best entries in the entire series too. It has a slight V-shaped sound signature going on here to also interest audiophiles and is capable of taking EQ quite well for those who want more bass. It's also the only one here that does not feel overly dark either!


Now we round off the MACH Series with the three most expensive sets, and once again I have some common ground with the MACH 60 making a re-appearance. These three are in a price range that is beyond the reach of most consumers and working professionals. I suspect it's more likely they will be provided via endorsement deals or by record labels to performance and music monitoring/mixing personnel than be paid out of pocket. They also vary enough to where the MACH 70 has also interested audiophiles. Indeed, nearly every single person I've spoken to who's listened to the Westone MACH Series of IEMs has found comfort with the bassier MACH 70 given the others go from neutral to warm at most in the lower frequencies. The MACH 70 takes a more pronounced V-shaped tuning that even managed to satisfy some bassheads I know, including the person who helped arrange all these review samples! I did not like it as much though, especially because I found the actual bass quality lacking. This was a classic case of BA timbre mixed in with a less dynamic set to where bass notes sounded artificial—especially on bass guitars and snares—and I thought a good quality planar or single dynamic driver set did bass better at a lower cost too. Indeed, I'd personally pick the MACH 60 over the MACH 70 since I also found it more resolving. It's only the MACH 80 that ends up winning in the detail retrieval metric and I do think it can hold its own against most IEMs for that, including several more expensive ones too. The MACH 80 would be my go-to for more serious music editing workflows, expecially with the upper mids responding to my liking. I'd still play with EQ to reduce the warmth slightly and tone down the 5 kHz peak to minimize sibilance, but I did like it a lot given it also has excellent imaging. I am just not sure I'd pay the extra cost over the MACH 60 though, which is still my overall winner of the entire series.