Acoustic Revive RHR-21 review

Acoustic Revive is one of the most prolific high-end audio manufacturers when it comes to dedicated, well-designed, and inventive accessories.

Designed by Ken Ishiguro, these accessories always go a step further than expected. Most of the time they are operating on the fringe of science, but I have not been disappointed by any of these Japanese products and I have had the opportunity to test, listen to, and review quite a few Acoustic Revive products over the years.

RHR-21

RHR-21 follows Ken Ishiguro research in the realms of Helmholtz-resonance theory.

Helmholtz resonance is the term for the phenomenon of air resonance in a cavity, named after the German physicist Hermann von Helmholtz. This resonance occurs when air is forced to move in and out of a closed space, causing the air to vibrate at a certain natural frequency. This principle can often be observed in everyday life, for example when air is blown across the opening of a bottle, resulting in an unmistakable resonant sound.

However, to make the best use of Helmholtz resonance, it is necessary to determine exactly where the cavity ends and the throat begins and how these aspects affect both the high and low resonant frequencies. How important is this distinction?

Resonant frequencies for the high and low ends must be exactly calculated and determined if the measured frequency falls within these ranges. The resonant frequencies of air columns depend on factors such as the speed of sound in the air and the length and geometry of the air column.

Longitudinal pressure waves are reflected from both closed and open ends, creating standing wave patterns. Crucial to understanding these standing waves is identifying the nodes and counter-nodes of pressure and displacement within the air column.

It is quite intriguing how Ishiguro managed to trickle down the primaries and the concepts into such a small, yet potent device. This took a lot of out the box thinking to being able to trickle down the technology that is usually implemented by far larger, absorber and diffusers into the device that can fit in the palm of your hand. But as you can read throughout the review, Acoustic Revive managed to encapsulate something very unique and highly potent, despite it given size.

The Music

As always, here are some reference titles and albums that summarize the advantages of the Acoustic Revive RHR-21.

Most importantly, the RHR-21 has succeeded in presenting the music more vividly without varying course or veering from the energetic, harmonic wholeness that is crucial to keeping its flow intact.

Zen Percussions – Yaslikazu Amemiya

Zen Percussions is one of my absolute favorite albums when it comes to obscure non-mainstream music, for a variety of reasons. I don’t think any other record I know of comes close to the sheer immediacy, lightning speed, and realistic reproduction of metallic percussion and its lifelike representation in acoustic space.

This is the record that can “break” the system immediately, as it requires a truly balanced and potent high-end audio system with its complexity, overtone density, and thundering energy.

I can instantly spot the differences as the album is deeply etched into my subconscious on so many replays because I like and love the narrative, and sonic escapism. It’s just something that touches my inner soul.

With the Acoustic Revive RHR-21, I was again more than pleasantly surprised at how the timbre, tone, and color adjusted to the music, and the sound projected more realistically when these units were placed in their intended positions. There was more control, and natural quietness, and somehow a sense of expanded virtual acoustic sphericity was taken further.

Conversation – Inada & Nakamure Duo

Another reference class record, again on the fringes of what is commonly referred to as consumer music, but again with a very different appeal that is very close to my heart. There is something about this record, the way it was recorded and the way it captures the harmonics and overtones that immediately shows what a balanced audio system is capable of and where its pitfalls lie, if any. With the Acoustic Revive RHR-21, not only was the overtone and harmonic density reproduced in a pleasing, natural way, but also without haste.

RHR-21 also helped to create a sense of better immediacy, and these Japanese room-tuning devices somehow brought a sensational peak in performance across the frequency spectrum.

This is particularly interesting because they do not just deal with one particular frequency band. They manage to cover a broad perspective and this is reflected in the lower, mid, and higher frequencies, creating a better feel for the instruments and how much more viable they are.

With the RHR-21, the music is much more focused, and the projection of the music in the three-dimensional acoustic space is less blurred and much more tangible, allowing the music to act freely and involving the listener in a deeper musical and listening experience.

Michael Franks – Tiger In The Rain

I was pleasantly surprised by the effect of the Acoustic Revive RHR-21 on “Underneath The Apple Tree” from the Michael Franks – Tiger In The Rain album. Especially with the horns, the obvious foray into the three-dimensional space ensured that they were not only more natural in the forte, but also gained more focus and solidified their three-dimensionality, revealing another layer underneath the sonic collage.

All too often, audio accessories can broaden the musical picture. In contrast, Acoustic Revive RHR-21 has proven with Tiger In The Rain that it is not a one-off, temporary performance enhancement, but a repeated act of balance.

And with many other tracks, RHR-21 brings the nature of attention to the fore, which again is unusual for such a small room tunning device as RHR-21.

The conclusion

As with anything that comes from mastermind Ken Ishiguro, these room tuners are something very special. Although the Acoustic Revive RHR-21 are quite small, they have a considerable weight when you hold them in your hand. These units are made from a solid block of aluminum with a perforated top and a solid brass metal base. The holes on the top of the devices are precisely calculated to achieve the most effective effect.

These unique devices are designed around the concept of Helmholtz resonators and must be carefully placed at strategic points where the energy accumulates. This can be done either near the speakers or by finding the exact focal points where the energy is accumulated and needs appropriate treatment. The pinpoint position can be measured or more easily found by playing a music track with the fundamental lover register impact. It can also be done by sweeping the pure sine wave signal at the sound at the frequency around 50 80 and 150 or even 200 Hz. With the last methodology, I have found relatively easy-to-work points for these devices to function effectively in my listening room.

Due to its patented, unique structure, the RHR-21 room-tuning device deals with eliminating standing waves when used correctly and should be placed in areas where these ripples accumulate, such as in-room corners, near speakers, or behind audio racks.

The RHR-21 is also devised to eliminate unwanted reflections, frequency clipping, and phase response in the listening room and to reduce frequency peaks and dips that affect the timbre and texture of instruments and voices. The result depends on the existing room’s acoustical treatment and careful placement, but when in place, it delivers a distinctive improvement in resolution by effectively removing sonic blur.

Once the high-end audio system is balanced and the electronics are optimally tuned, it’s usually time to add high-end audio accessories. 

Without these basic steps in tuning, voicing, and finally balancing the system, there is no way that any accessory will work to the advantage of the system, but will only distract the listener from the real goal, and that is the best possible reproduction of the music. 

Acoustic Revive is one such product that can take the balance of the system to a new level of performance, but it needs clever and well-thought-out positioning in the audio system. When this criterion is met, the RHR-21 can make a notable difference in sound reproduction, and when it is in its intended place, it shows its potency easily, and the effect is not moderate by any means. It can bring a far greater benefit to the overall performance of the system than its proportion would suggest. This is particularly interesting because, as written in the music section, it touches the harmonic structure of the music, more specifically, the harmonic density and tonal overlay, along with a richer sound projection, and that alone is a great compliment and highlight.

Interestingly, with the RHR-21 in the right places, the decay and delay times are not a flash in the pan, but come closer to reality, reflecting the lifelike reverberation of the notes.

Acoustic Revive RHR-21 also reduces the artificial glare that too often pushes the sound into brittleness, and naturally enhances luminosity by somehow tinkering with the music’s millisecond timing without altering the precision or speed of the attacks.

Too often the value of something is measured by how and what exotic materials are used, or by esoteric techniques. The Acoustic Revive room tuner takes the raw science and brings it into the realm of the unabashed spirit of music that satiates the listening experience.

While at first glance Acoustic Revive RHR-21 may be seen as a smattering of approaches, in reality, it exceeds expectations. Although it is a passive device, it operates in the realms of an active apparatus and, unlike many tuning devices, easily transcends the act of mere existence.

I am happy to award the Acoustic Revive RHR-21 with the 2024 Mono and Stereo Highly Recommended Product.

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Pricing

  • US$1800 per/unit

Specifications

  • Weigth 876 gram
  • Dimensions Ø51×164 mm

Contact

MuSon Project, Inc.

Web: acousticrevive.jp

Email:y-hontani@musonpro.com