There seems to be no dedicated Thread on this topic. A lot of people asking questions with answers varying broadly in quality and surprisingly, even a lot of reviewers seem to be very confused about that.
I already explained it in the Thread about general Etymotic and Westone Audio discussion, but that is one post in an Thread covering lots of topics, so hard to find for people looking for that information. So i thought, once and for all, explain how the lineup works so i can reference to this thread when i get asked myself (scratch your own itch
)
8 IEM from 10-80, sounds like a lot and confusing, but its simpler than most people think. The MACH Series is divided into 3 lineups.

So the MACH 20 is the ""flagship"" of the Entry Lineup. The 70 is the flagship of the Bass Lineup and the 80 is the flagship of the Reference Lineup
The difference between the Bass Lineup and the Reference Lineup is the bass BA. Quite a few people (including reviewers) get confused on why the Bass Lineup has one bass BA while the Reference lineup has two bass BA.
Size does matter in the end. Here you have an comparison of the bass BA in the MACH 70 compared to the two bass BA in the MACH 80


The Bass Lineup has only one, but an significantly larger one, while the Reference Lineup has two smaller ones, resulting in an faster and more accurate bass representation.

So even though looking confusing at a first glance, it is simpler than one might think. Its a decision of budget and what target want. You want fat bass? Check the 30/50/70 and choose the right one based on your budget. You want a reference sound, its 40/60/80 and your budget.
Bonus Question 1: What is the difference to the Pro X Series?
The Pro X Series are pure Stage Monitors that still can be used for music listening, but have not been designed with that in mind. In general, they sound even warmer and less balanced than the Bass Lineup. So if the Bass Lineup is not warm enough for you and you want more bass/fatter sound, the Pro X Lineup has you covered. They are also smaller and so can be more comfortable to some.
Bonus Question 2: What about the Earpieces
Westone delivers Earpieces in 5 Sizes that are coded by color
My recommendation (and the only ones i used when testing) are the TrueFit, so the foam earpieces.
Bonus Question 3: Is the Mach 80 very bright? Is it harsh? It has 4 BA for the Treble
Absolutely not, the opposite. Its 4 BA for the treble are not used for tuning but to keep distortion as low as possible. So even though having 4 BA for the treble, the Mach 80 is not an bright IEM and not hot/harsh or fatiguing.
Due to the low distortion, its less harsh than a lot of similar tuned IEM that only have 1 BA for the treble. Those BA are there for Quality, not for Quantity. If you're afraid/dislike bright IEM, do not worry. Its perfectly flat/balanced. It does sound clear/detailed/resolving, but it is not bright and/or has an insanely large soundstage or something like that. It is a Studio Reference Monitor and sounds like one.
Bonus Question 4: What is your personal preference
As an 80 owner, I wrote a review about it: https://www.head-fi.org/showcase/westone-audio-mach-80.25894/reviews#review-35098
If there are any followup questions, i will update this post =) feel free to ask any.
I already explained it in the Thread about general Etymotic and Westone Audio discussion, but that is one post in an Thread covering lots of topics, so hard to find for people looking for that information. So i thought, once and for all, explain how the lineup works so i can reference to this thread when i get asked myself (scratch your own itch

8 IEM from 10-80, sounds like a lot and confusing, but its simpler than most people think. The MACH Series is divided into 3 lineups.
- Entry
- Friendly to your budget
- Except for the sound, provides the features of the more expensive models
- Same Shell/Comfort/Isolation/IP68 rating
- Pelican Case that is slightly smaller
- Bass
- Probably what a lot of people want
- They are based on an flat and accurate reference tuning, but with pushed bass
- Warm and Musical Listening experience and so also excellent choice for stage use
- There is no push in the upper mids/treble to counteract that. They will sound muddy/muffled to some
- Reference
- Flat and accurate frequency response
- Ideal for but no way limited to critical and analytical listening with an very harmonic and balanced sound
- Studio Reference Monitors and hence can be used for mixing and mastering music

So the MACH 20 is the ""flagship"" of the Entry Lineup. The 70 is the flagship of the Bass Lineup and the 80 is the flagship of the Reference Lineup

The difference between the Bass Lineup and the Reference Lineup is the bass BA. Quite a few people (including reviewers) get confused on why the Bass Lineup has one bass BA while the Reference lineup has two bass BA.
Size does matter in the end. Here you have an comparison of the bass BA in the MACH 70 compared to the two bass BA in the MACH 80


The Bass Lineup has only one, but an significantly larger one, while the Reference Lineup has two smaller ones, resulting in an faster and more accurate bass representation.

So even though looking confusing at a first glance, it is simpler than one might think. Its a decision of budget and what target want. You want fat bass? Check the 30/50/70 and choose the right one based on your budget. You want a reference sound, its 40/60/80 and your budget.
Bonus Question 1: What is the difference to the Pro X Series?
The Pro X Series are pure Stage Monitors that still can be used for music listening, but have not been designed with that in mind. In general, they sound even warmer and less balanced than the Bass Lineup. So if the Bass Lineup is not warm enough for you and you want more bass/fatter sound, the Pro X Lineup has you covered. They are also smaller and so can be more comfortable to some.
Bonus Question 2: What about the Earpieces
Westone delivers Earpieces in 5 Sizes that are coded by color
- Short Earpieces
- Small (Green)
- Medium (Black)
- Large --> Does not exist(!)
- Long Earpieces (Higher Isolation, more stable fit)
- Small (Blue)
- Medium (Red)
- Large (Orange)
My recommendation (and the only ones i used when testing) are the TrueFit, so the foam earpieces.
Bonus Question 3: Is the Mach 80 very bright? Is it harsh? It has 4 BA for the Treble
Absolutely not, the opposite. Its 4 BA for the treble are not used for tuning but to keep distortion as low as possible. So even though having 4 BA for the treble, the Mach 80 is not an bright IEM and not hot/harsh or fatiguing.
Due to the low distortion, its less harsh than a lot of similar tuned IEM that only have 1 BA for the treble. Those BA are there for Quality, not for Quantity. If you're afraid/dislike bright IEM, do not worry. Its perfectly flat/balanced. It does sound clear/detailed/resolving, but it is not bright and/or has an insanely large soundstage or something like that. It is a Studio Reference Monitor and sounds like one.
Bonus Question 4: What is your personal preference
As an 80 owner, I wrote a review about it: https://www.head-fi.org/showcase/westone-audio-mach-80.25894/reviews#review-35098
If there are any followup questions, i will update this post =) feel free to ask any.
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