Today we’re talking about the Meze Astru, a single dynamic-driver IEM that comes in at $899. But rather than making this just another review, I want to use the Astru to demonstrate something far more important: why people hear IEMs so differently from one another.
I’ve covered this before, but during a recent members-only livestream where I was evaluating the Astru, I used the individual HRTFs we got from our trip to London—mine and Griffin’s, specifically—to show just how dramatically two people can perceive the same IEM. Whether the Astru is “for you” or not, this is information people need to see.
Disclaimers
This unit was provided by Meze for evaluation. They haven’t asked me to say anything, and they certainly haven’t paid me to say anything. All thoughts are my own.
Design & Build
The Astru is Meze’s latest single dynamic-driver IEM. It’s beautifully understated—small, comfortable, and visually reserved in a way most high-end IEMs are not. None of the gaudy, over-designed excess you often see in this bracket. Just clean, classy industrial design with a normal color and unobtrusive look.
The wishbone-style Y-split is unique, the cable feels good in hand, and everything is ergonomically sound. No complaints here.
Generally everyone liked the industrial design of the Alba, and the Astru seems to take what worked there and just elevates it with better materials. No complaints here.
Why IEMs Are So Personal
We’ve spent a lot of time understanding how our heads and ears shape sound—and now we can meaningfully apply that to IEMs.
When you insert an IEM, the pinna (outer ear) is bypassed. The outer ear that normally contributes key resonances and filtering simply doesn’t contribute, but importantly, your brain still expects the contributions of this filtering. That means the IEM tuner has to approximate what the average listener's brain expects to hear, and this is why when evaluating IEM measurements, we use an HRTF that approximates average human outer ear effects—JM-1 Diffuse Field, which is based on ISO 11904-1's human HRTF average.
This is one crucial reason IEMs are inherently personal, but its also not the only reason. Another important reason is that people's ear canals are different sizes, and the difference in canal length has effects on the actual sound the IEM itself produces—larger overall canals will propagate bass a little less effectively, and longer ear canals will shift the pattern of resonances in the treble lower in frequency. A different ear canal will also affect the overall HRTF the listener expects, so in general, when it comes to sources of variation for IEMs, there's a lot that has to be taken into consideration...
...and that's why it's not exactly easy to say "This IEM is good" or "This IEM is bad" with any real confidence that this is how it will sound to any given person other than me.
For measurements, we use the B&K 5128, whose 4620 ear simulators are part of the system—not a separate rig. This gives us a consistent baseline, but that baseline still reflects a population average, not you, and not me.
Thankfully though, due to our trip to London, we can now literally visualize how each of us hears an IEM.
How the Meze Astru Measures
When the Astru is measured on the 5128 and compensated with the JM-1 Diffuse Field baseline—representing how the average person is likely to hear it—I’d describe it as mildly W-shaped: Elevated bass, a forward region around 1–1.5 kHz, and a slightly quirky treble with some fatiguing hotspots.
For the average person, this sound profile will likely have something fun for those seeking detail, dynamics, and texture, but it does so while also introducing colorations—especially in the treble—that may skew timbre.
How I Hear It
If we substitute my HRTF into the baseline, we get the version of the Astru that I actually hear.
And it’s… rough.
The Astru becomes distinctly W-shaped, with fatiguing low/mid-treble peaks and a comparatively dark mid/upper treble, creating a sense of harshness, incoherence, and a "compressed" sounding imbalance. Cymbals sound crunchy and harsh, and most percussion loses any claim it has to natural timbre. I do not enjoy its treble at all, and it really ruins how this IEM would otherwise sound for me.
How Griffin and Cameron Hear It
Griffin’s HRTF yields a different picture: More forgiving low/mid treble, because Griffin's HRTF is basically identical to the JM-1 Diffuse Field in the lower treble, but the sound also becomes extremely elevated in the upper treble. While Griffin hasn't yet heard this IEM, I can be almost certain that his typical complaints about spicy upper treble would be present with this IEM.
Cameron’s HRTF yet again produces a unique response—with about the same level of lower-treble glare that I get, but with even less upper treble to balance this elevation out.
This goes a meaningful distance to confirming a consistent truth:
No two people are going to hear the Astru the same way, and its likely that people will have valid reasons not to enjoy the sound profile here.
With this system, I can now predict with reasonably high confidence how others on the team will perceive an IEM—even before they listen to it.
So… Is the Astru Good?
For me, the Astru has too many out-of-bounds regions—especially in the treble—to be enjoyable long-term.
Yes, it hits hard. Yes, it’s textured and dynamic. But it’s also quirky, colored, and fatiguing in ways that make cymbals and percussion sound wrong.
But—and this is crucial—that’s my experience, not an actual, objective characterization of the product itself.
Your own anatomy may bring those regions back into line. Or it may not. And this is why you really do have to hear things before you buy them.
Thankfully, Headphones.com offers a 365-day return policy, which is exactly the kind of safety net you want for a product category this variable. If you understand the sources of variation we're outlining here, you know you'll want to try an IEM before committing to it fully. Headphones.com's return policy allows you to do this without worrying too much.
So if you value the work we do, or want to try an IEM or headphone before committing the full spend on it, consider checking out Headphones.com next time you’re shopping for headphones or IEMs.
Conclusion
The bass is excellent—authoritative, weighty, fun—and the midrange is... fine. It's a bit forward and quirky, but not objectionable. But the treble is very difficult for me personally. This isn't an IEM I really enjoy listening to or have any desire to keep listening to, so for me, it doesn't quite hit.
Sound Quality Score: 4.4/10
Overall Score: 4.8/10
This is a companion discussion topic for the original entry at https://headphones.com/blogs/reviews/meze-astru-impressions-i-expect-this-to-be-controversial
