Hey - not yet known full details, hopefully will be release towards later part of the year. In a way, you can see it almost a light version of EJ10, shared many similarities but obviously EJ10 will have much better mids, treble
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If it will end up being the same Tuning as the Prototype at High End Munich it’s gonna be very impressive and imho a clear step up from EJ07m.
I even favoured it above EJ10 at first listen until i started to realize the differences.
They are really quite similar in their presentation.
What stood out on both for me was the very clean and structured midbass presentation making room for a super clear and energetic midrange without being fatiguing.
The main difference for me was clearly the EST treble from EJ10
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Wait, doesn’t Serenade also have 4EST?
I wonder how it differs from EJ07 Original…
@Jon_let would love a graph of Serenade 
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Afaik it will have PZT drivers for the treble.
It has much more energy than EJ07
More sub, more energetic mids and more treble, it’s a very detailed set but i was still able to crank it quite a bit
Serenade should* have a micro-planar for treble, nothing is finalised yet as our focus has been the EJ10, as Rinderkappajoe mentioned, both shared similar presentation but EJ10 has 2 more BAs so that helped mids, even treble quite a bit more. EST implementation in EJ10 is also a huge step up in my opinion, more airy, buttery like and effortless. Compared to planar, the timbre and texture might not for everyone
Edit* - this is one of the very early versions, the latest we had in Munich HighEd featured our own developed micro-planar for treble. It is very good but timbre & Texture might not be for everyone
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Following up with my impressions of Cadenza 4
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Very comfortable fit, if not the best I have had so far. Its very much like Mystic 8 but more lightweight and therefore even better.
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I was not the biggest fan of the design judging from pictures but in hand I like it quite a bit, especially the matte white shells which have a really good feel to it. The Faceplate is very simple but fits the overall design.
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Cable is of very good quality, some might dislike the swappable L-shaped terminations though. (I ended up using one of my cable as you can see in the pictures but that does not mean I disliked the original one, was just playing around
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I´d describe the overall presentation as clean and energetic with plenty of details and an openness that makes it quite appealing to me.
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Subbass is lacking in quantity for bass heavy music. (easy eq)
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Midbass is very fast with a lot of texture and does not bleed into the mids at all. I like this kind of tuning for max. clarity throughout the midrange
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The mids are energetic and slightly bright which gives vocals that certain pop/emotion to stand out a bit.
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Treble is pretty detailed but some might want more air frequencies. To me the treble fits the overall signature quite nicely and because the midrange is already a bit bright it helps to avoid fatigue. Compared to something like Mystic 8 or Cadenza 12 the treble is less refined and in direct comparison sounds a bit gritty sometimes.
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What really stood out to me was the overall technical performance at that price point. It´s easily on the level of EJ07m/Yanyin Mahina/Xenns Top and so on and I would not miss anything here if C4 would be my only IEM to be honest.
In conclusion C4, with its 1DD and 3BA, is a really competent IEM that I have seen go for less than 200€ which makes it an absolute bargain.
I wanna thank Audiogeeks Europe for being part of this tour and of course thanks to Letshuoer for providing a demo unit!
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Thank you for the info-dump!
If I may be so bold, here’s what I would be very interested in.
Letshuoer EJ07 - 2026 Edition (Resin shell)
2DD/2BA/4EST
Pricing? All I know is the Monarch Mk4 is $1149 with a 2DD/6BA/2EST config, all sonion - so lower than that.
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I would say its a good direction, this is what my personal CIEM started off initially, then with the team we added more bass (way more), plus enhanced mids (a lot note weight, resolution and ensure mids remain crisp despite the elevated bass) and then improved EST implementation = end result became the EJ10… Serenade will continue its dev journey, probably can be seen as mini EJ10
In order to keep tonality in sync, we had to bump the treble a bit too
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I’m glad that the EJ10 and Serenade are being made, but I’m convinced they aren’t designed for high-volume listening.
The EJ07’s legendary status came from its tuning, which encouraged cranking up the volume by aligning with the Fletcher-Munson curve, keeping bass and treble below the mids for a balanced-once-loud friendly sound.
By keeping the energy above 10kHz roughly 4-5dB under the midrange, you gain superb 3D staging and depth, which is another ingredient in its awesome sound.
Please consider perfecting this concept in the future, thank you!
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Thanks bud, I love 07 OG and like many, you are absolutely right it’s a monster with vol scaling. Many of our fans are part of this “short bus” - some of those in the AudioGeek tour group in Europe have demo’ed the EJ10 engineering unit and placed order EJ10 (everyone demo’ed placed order already), I think once we able to produce EJ10, many will love it. Since you are one existing 07 OG fan, I think you will love EJ10 too.
Personally I called it our new king taking our EJ series to new height, perviously EJ07 OG not able to, stayed tuned as soon as we have the units ready will be sending out for reviews etc. And I will hopefully have some for upcoming CJ London in around 3wks’ time
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Nice review.
The more I read about the C4, the more it seems to be a sleeper hit or overlooked gem. Very little hype, but everyone who has heard it enjoys or loves it.
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Thanks!
Yeah this hobby is strange sometimes and some sets get all the hype and a few months later no one talks about them anymore.
There´s also way too much new stuff coming out to keep track (Yes i am looking at you Ziigaat :-D).
It took me quite a while to finally demo C4 but i was always very curious about it.
Really appreciate the possibility to demo so many sets within the Audiogeeks community 
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Pricing is not only a more drivers more money game, besides 2 EST cost more than 6 BAs at least…
A crimson has 4 BAs but cost more than a monarch, and sounds better as well!
But there is some sort of correlation often.
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Depends on the BAs actually. The cheapest ones for sure are cheaper but the more expensive BAs from Knowles/Sonion may be more expensive than a dual “EST” from Sonion.
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Allright! seems i’m not up to date with driver prices then. I just know that the EST monopoly has lead to them becoming even more expensive over the years. rare for a electronic technique/device.
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Thieaudio is also part of a big company where Symphonium is, like, 5 dudes. A lot of what you are paying for is margin against scale to manufacture as well as a “bespoke” product.
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Example would be this BA
https://www2.mouser.com/ProductDetail/Knowles/CI-22955-000?qs=3unH%2FDqlvl8EWdn2%2BxaxZg%3D%3D
6 of those at the max discount there, 22 usd would be 132 usd.
Even a quad EST here.
https://www.aliexpress.com/item/1005006257872036.html
is cheaper.
But yeah atm Sonion is the only one afaik with a “EST” like this
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yeah, and the know how, build etc etc.
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I thought it was 200+ but the more you know! tack!
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I’ve been waiting for Serenade since canjam SoCal 24–it scaled well with plenty bass and amazing female vocals. So are you saying that Serenade evolved more into EJ10 and serenade’s EST s got switched out to microplanar? When will EJ10 be available to order?