Auditory Delight
As a musician and life-long audiophile, I require my iems to reproduce sound from a variety of instrument types as naturally and realistically as possible to be satisfied. Today there are a plethora of HQ in-ears available. I read many reviews of highly-ranked versions from well-respected makers before deciding to purchase Westone Mach 70s. If you are considering buying these be sure to read their reviews because now that I have listened to them I think all the descriptions I found for their performance and design characteristics to be accurate. Foremost to me among my criteria for choosing an iem is its sound -duh (refer to reviews). In addition, I scrutinize choice and quality of its driver components to reproduce a target tuning. Lastly, I consider its included matched cabling, form factor/housing material, and quality of fabrication assembly. An iem that has a compact design and is ear-comfortable is also important to me, and the 70s (and Mach line) have that. I pair them solely with an excellent DAP but I have no doubt that they will please discriminating listeners using any HQ source and recording.

So far, a great set of earphones
I've only had these a few days and so far I like. I also own the Westone W80. I like that these seem to be a little warmer that those. The bass seems to a little more pronounced. Again, so far: great.

Worth every penny!!
I've been performing and listening with headphones and IEMs on stage, in the studio, and more recently, on YouTube for over 25 years. The level of physical comfort and clarity of sound in the Mach 70s have created the best experience to date. Highly recommended!

What new things will I hear from my favorite classics with the Mach 70?
I wanted to give these new earbuds/IEMs a decent listen before writing a review. I've had them now for 6 weeks and have probably listened to them at least 100 hours at this point. The source was a lossless streaming service and high resolution MP3s through my phone to an Audioquest Dragonfly Cobalt with the ESS Sabre DAC in it to bypass the phone's amp and marginal DAC. I took a risk over a decade ago on my first good pair of earbuds with the Westone W40s. It was stunning how well the mids and highs were articulated, but it didn't have the bass I wanted. Sadly I lost those and replaced them with some B50s which had fantastic bass but not as much mid and treble articulation as I had with the W40s. It was time to put some serious $ toward what I was really looking for, which was a merging of the succulent mids and highs of the W40 with the bass of the B50. So I ordered the Mach 70s after reading a few indepth reviews of them hoping this would be the end of my search for the perfect sound when I am in the office or out and about.

And it was! I love these

I'll just say the online professional reviews were spot on. Sweet punctuated sound reproduction, rich powerful bass, very well balanced. I love listening to these. And the 4 treble drivers bring out so much detail I'd never heard before in songs I've listened to for decades. One in particular was live recording of a Bruce Hornsby song where he tells the crowd that JT, one of his musicians, just learned the song and to pay close attention to him. I had never heard this before but just faintly and clearly hear someone in the back of the theater yell out "Go JT!" What a thrill! I'm not going to go on and on about all the other details these Mach 70s will reveal when you listen to them, but you will hear so much more in your music. And the various instrument sounds will have more 3 dimensionality and accuracy than you probably ever heard before if you are new to this audio gear at this level.

One thing that was an interesting difference between the discontinued B50s and the Mach 70s was I used the foam tips on the B50s to get more bass than I could get from the silicone ones. So I started with the foam tips on the Mach 70s. I'll just say when you buy the Mach 70s, you need to spend a few hours with both the foam and silicone tips. There is a difference. Unlike my experience with the B50s, the Mach 70s had rich strong bass with the silicone tips as well as foam. The one big difference though for my ears were the highs on the Mach 70s. With the foam tips I was concerned because the highs were a bit too prominent and fatiguing. I am extremely sensitive to high frequencies. I have to wear earplugs when throwing glass in the recycle bin because that bright crashing sound of breaking glass is excruciating. Anyhow, with lesser source material like lower bitrate MP3s in my collection there was a lot of almost painful sharpness to the sound with the foam tips (the lossless tracks didn’t present this problem though). Still, I started to worry maybe these Mach 70s were not for me and I looked up how to roll off the highest frequencies maybe 5% to match the mids and bass. But then I switched to the silicone tips. That fixed the issue! I didn't lose any of the bass but for some reason those tips tamed the highs to where they became perfectly balanced for the particularities of my ears. So when you buy these be sure to try both types of tip.

The other concern I had was why they only have 1 bass driver instead of 2 like the Mach 80s. In reading online reviews they said the Mach 70s had rich, fun, strong bass, and maybe even more than the Mach 80s. I didn't try the Mach 80s but they apparently its two bass drivers are not as intense when it comes to bass as the single driver in the 70s, and I do want intensity. It is amazing how the single bass driver pushes out great low end, so don't worry about missing out on bass!

The thought that keeps going through my head is the Mach 70s not only reproduce music extremely well, but celebrates how well our ears can sense the auditory world around us. So why give them something inferior with lesser products? I seriously doubt you will be disappointed with these.