I finally pulled the trigger on these speakers:
https://hasehiro-audio.com/product/umu-191m/I fell in love with these based upon this video coming up on the ol' youtubes.
https://www.youtube.com/watch?v=q2IvlqMaH4UHere is another great video about the journey:
https://www.youtube.com/watch?v=yTCtitxkNvc(You will probably need to enable the translated subtitles)
There is something just right about them in aesthetics. The construction and the texture lines routed into the laminated layers really just work. I fell in love with them, and the old man who makes them is just charming.
Now for the multi-month wait...
I think what trips me out the most is the paper resonators. Here is what ChatGPT says about them:
Ah — yes, that’s a fascinating and very Japanese bit of acoustic artistry.
What you’re seeing in the Hasehiro back-loaded horn (and in some other Japanese full-range designs) — those little paper tetrahedrons or pyramids glued into the internal corners of the compression or rear chamber — are what they call paper resonators (紙共鳴体 kami-kyōmeitai).
They’re not purely decorative; they serve a subtle but important acoustic function.
🌬️ 1. What it is
A “paper resonator” is essentially a tiny tuned resonant cavity — usually a hollow paper structure (often a folded tetrahedron, pyramid, or cone) with thin walls.
Because it’s extremely lightweight and stiff for its mass, it has a very high Q resonance in the midrange region (typically 400–2 kHz).
Hasehiro installs them in specific points — especially the rear chamber corners, where standing waves and reflections tend to concentrate.
🎶 2. What it does
The idea is not to act like an absorber (which would turn sound into heat) but rather as a resonant damper or diffuser that:
Breaks up strong reflections in the rear chamber,
Broadens and randomizes the phase of internal resonances, and
Converts sharp resonant peaks into a more benign, “musical” decay.
In other words:
Instead of a single strong cavity resonance causing coloration, you get many tiny, lower-energy resonances that smear the energy in time — perceived as a smoother, more natural tone.
It’s similar in spirit to Helmholtz resonators or the little “resonance boxes” you see in Japanese instruments — but on a micro scale, and tuned empirically by ear.
🔬 3. Why paper?
Paper (especially washi or handmade paper) has:
Very low internal damping (so it rings gently rather than deadening),
A natural gradient of stiffness and density, and
Excellent self-noise characteristics — it “breathes” instead of rattling.
So the resonator sings along softly with the enclosure instead of fighting it.
Think of it as a sympathetic resonator, like the soundboard ribs in a violin.
🧭 4. Effect on the horn/driver
The Hasehiro designer (Mr. Hasegawa) uses these to refine how the rear wave couples into the horn throat. They help ensure that:
The upper mids reflected back toward the driver are de-correlated,
The horn’s low-frequency loading isn’t contaminated by chamber coloration, and
The overall timbre feels more “open” and “live.”
It’s one of those elegant low-mass, high-craft solutions that you’ll almost never see in Western loudspeaker design because it doesn’t show up on measurements easily — but it can make a subtle subjective difference.
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