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Sweet spot of the upgrade cables? - Effect Audio Horizon Series 2025
In this blog, I would like to introduce the cables of the new "Horizon Series" from Effect Audio:
Fusion 1 (2025)
Like the predecessors, these are solid-core cables, meaning cables with a solid core made from a strong strand (16.5 AWG), which is wrapped with thinner strands and additionally insulated.
While the predecessors Code 23 & 24 were much more colorful (blue, violet), in 2025 a more conservative look was chosen. Personally, I liked the "old" cables with bright insulation, but the "new" ones simply fit better with various setups and certainly polarize less.
Besides the exterior, of course, the focus was also on the inner values, and the cables were redesigned from the ground up to both improve the sound and enhance usability - the new Code cables are significantly smoother than the old ones. While I could confidently recommend the old Code 24 especially for large headphones, the new cables are now definitely also excellent for IEMs!
Sure, braided cables are still more flexible, but the new Horizon series can now also be used "on-the-go" without any worries.
Oh yes, you can still order the new Horizon Series cables as headphone cables. Please write to us at: info@audioessence.ch or call: (+41) 77 403 35 26.
Playback partner
Source
IEMs
- Noble Audio Kronos with original cable: (palladium-coated 4N pure silver and 6N OCC silver)
-
64 Audio U4s with original cable
The Noble Audio Kronos (4199 CHF) is a true flagship IEM and already comes with a very high-quality and expensive original cable. Therefore, the question initially arises whether the cables of the new Effect Audio Horizon series even make sense on a flagship IEM with a high-end cable. After all, they are priced more in the mid-range of upgrade cables and thus not necessarily intended for IEMs > 4000 CHF/USD.
But I wanted to deliberately approach the matter from the other side and see how well "midrange" upgrade cables can keep up with an absolute flagship IEM with the included flagship cable.
The original cable for the Kronos was carefully selected and custom-made and fits - in my opinion - perfectly with the Kronos. Finding a meaningful upgrade cable here is certainly not easy and is likely to be costly. I am all the more curious to see how the new Horizon cables from Effect Audio perform on the Kronos.
I would describe the sound signature of the Kronos as a reference tuning. Very balanced with slightly elevated bass, plenty of "sparkle" in the highs, wonderfully natural voices, and a very realistic soundstage.
A purebred flagship IEM that lives up to its price and guarantees hours of fatigue-free music enjoyment. In my opinion, the best tuning Noble Audio has delivered so far and therefore also ranks high on my favorites list of the best IEMs of 2025.
I think the Kronos is therefore very suitable as a (cable) test subject, especially in combination with my "workhorse", the infallible Lotoo Mjölnir!
The 64 Audio U4s is priced at 1199 CHF, placing it in the premium segment. Unfortunately, the included cable can only be described as cheap and extremely inadequate. Of course, 64 Audio comes from the professional sector, and on stage the cable doesn't matter since the sound is transmitted via a wireless link anyway.
For music lovers, the included cable "holds back" the capabilities of the U4s, because the U4s definitely has potential - provided the right cable is used!
Effect Audio Code 23 MKII (Solid Core UP-OCC pure copper cable)
The new Code 23 MKII is made of pure copper and is thus the cheapest cable in the test. (649 CHF)
Noble Audio Kronos
Compared to the truly excellent original cable (which is significantly more expensive than the Code 23 MKII), the Code 23 MKII delivers slightly less bass impact. Texture and speed remain largely preserved.
The sound signature is overall slimmer and less full-bodied than with the original cable. The highs are a touch softer or less pronounced, the voices are very natural and still in the foreground but are no longer outlined or emphasized as clearly as with the original cable.
As expected, the (significantly more expensive at about 1200 USD) original cable wins here, but the differences are less drastic than one would expect. The Code 23 MKII is overall a bit "tamer," yet the wonderfully balanced reference sound signature of the Kronos remains intact.
I can well imagine that the Code 23 MKII would be great for IEMs that have somewhat too much/too sharp treble and too intense bass, like the Kronos predecessor Noble Audio Viking Ragnar.
64 Audio U4s
The U4s from 64 Audio are tuned rather "warm" from the start with omnipresent sub-bass, which gives the sound a certain fullness and emotionality but also causes other frequencies to be partially masked.
Voices are sonorous but not in the foreground; sometimes they almost get lost in the orchestra. There are enough details, and the treble goes quite high, but this comes at the cost of some "sibilance." Overall, the sound feels slightly "veiled," as if a veil is spread over it.
Completely fine for IEMs in this price range, but not exceptional. The U4s are simply "mass-market", meaning they are tuned quite bass-heavy.
The question is: Can we improve them with the Code 23 MKII and unlock hidden potential?
It is immediately noticeable: The Code 23 MKII delivers significantly more bass impact on the U4s, but the previously omnipresent sub-bass is significantly reduced and the bass is faster and more defined than before.
This results in voices now standing more in the foreground, clearly separating from the ensemble and sounding much more natural - very nice!
Oh yes: The veil I mentioned earlier has disappeared. The U4s delivers significantly more detail, but also clarity. A slight sibilance (hissing sounds) is still present in some tracks, but much less disturbing than with the original cable.
The U4s also gains in spatiality and the channel and instrument separation is significantly more pronounced.
Overall, the Code 23 MKII elevates the 64 Audio U4s to a new level and turns it into an audiophile fun machine!
Who/what is the Code 23 MKII suitable for?
The Code 23 MKII is suitable for premium (around CHF 1000) to midrange (up to CHF 2000) IEMs that come with a poor to mediocre cable. The Code 23 MKII solid-core copper cable can potentially improve the entire sound spectrum here and turn a mediocre in-ear into a really good one!
Effect Audio Code 24 MKII (Solid Core UP-OCC copper cable with silver coating)
The new Code 24 MKII consists of silver-coated pure copper and is priced in the mid-range of the test (849 CHF).
64 Audio U4s
The bass, which was already significantly stronger and better contoured with the Code 23 MKII, remains with the Code 24 MKII but gains even more contour, speed, and especially texture.
Voices are even more prominently highlighted and gain in verve and intensity, also compared to the Code 23 MKII.
For the first time with the U4s, I can really talk about "sparkle" in the highs, and although this is a silver addition, tracks with overly prominent sibilance are not presented more sibilantly but surprisingly more silky.
Overall, the performance gains significantly in intensity and space – and so clearly that I find it hard to believe that it is still the U4s with which I am listening to music.
While the Code 23 MKII was already a clear upgrade, the Code 24 MKII brings the 64 Audio U4s into the next higher sound class! However, the trend here moves away from the audiophile fun machine towards a serious audiophile (reference) IEM!
Based on my many years of experience with hundreds of IEMs and just as many upgrade cables, I expected improvements. But that they would be so significant really surprised me! .😮
(Oh yes, I find that both Code 23 and Code 24 MKII look excellent with the U4s!)
Noble Audio Kronos
I deliberately start the comparison with the Code 24 MKII and not with the original cable to exclude any potential "bias" on my part. After all, a few days have passed between my Kronos tests with the Code 23 MKII. So I can no longer really compare from memory.
Compared to the 64 Audio U4s, the Kronos is a completely different "beast" and this becomes clearly evident from the very first bars.
In conjunction with the Code 24 MKII, the Kronos throws voices at me with passion and guitar strings sound incredibly realistic. The bass is tight, fast, and well textured. The space is clearly and realistically depicted, each instrument can be distinctly located in the space.
And then again that vocal reproduction that immediately triggers emotions in me. 😍
The highs are extremely detailed and direct with plenty of "sparkle"—wow!
Does the original cable still do it better?
Now it’s getting tight! The Code 24 MKII "sneaks" close to Noble's original cable but can’t quite outrun it.
Voices come through a bit more intensely with the original cable, the bass is fuller, the highs a touch silkier, and the spatiality a bit more—well—spatial. 😅
Channel and instrument separation are also somewhat more pronounced than with the Code 24 MKII.
I am deliberately doing this test with an absolute flagship IEM like the Kronos, which, unlike many other flagships, also comes with a cable appropriate to the price, because I want to explore both ends of the spectrum.
Who/what is the Code 24 MKII suitable for?
That you can push a U4s this far sonically really surprised and impressed me!
The Code 24 MKII thus ventures into new territory and, in my opinion, is suitable not only for the premium or upper mid-range but also for true flagship IEMs that do not already come with an excellent cable like the Kronos.
For example, I am thinking here of all flagship products from 64 Audio and FiR Audio, and the excellent Elysian Audio Labs Annihilator 2023 will also clearly benefit from this cable. Yes, the Anni comes with a pretty good cable (around CHF 400), but it still has significant potential upwards, as my own tests in the past have shown.
Effect Audio Fusion 1 2025 (UP-OCC gold-plated silver, pure silver, and nearly half a dozen high-quality copper variants)
The heart of the Fusion 1 is EFFECT AUDIO's most complex construction to date. They call it the "Tri-Strata Layering™ (TSL) geometry." Three precisely engineered layers combine UP-OCC gold-plated silver, pure silver, and nearly half a dozen high-quality copper variants, including an improved ergonomic solid core copper at the center. The Fusion 1 is the most expensive cable in the test field and costs 1199 CHF.
What immediately stands out: The Fusion 1 is noticeably smoother and more flexible than the two Code 23 & 24 cables, which is probably due to the more elaborate construction, reflected in the price alongside the finer materials.
The only important question is: How does the top cable of the new Horizon series change the sound of our test IEMs?
Noble Audio Kronos
Price-wise, the Fusion 1 is on par with the cable supplied by Noble. That doesn't mean much, as the "standard cable" from Noble was specially tailored for the Kronos. Nevertheless, my expectations for the Fusion 1 are high.
... and I am not disappointed. The Fusion 1 actually manages to top the already excellent original cable of the Kronos. Wow! 🤩
What immediately stands out is the confidence in the music presentation. The first terms that come to mind when listening are "rich and smooth". The sound gains fullness, volume, in short, confidence. The bass is the strongest of all tested cables, but also the best textured.
Voices are slightly pulled back again compared to the original cable and the Code 24 MKII, fit perfectly into the ensemble, sound even more natural, and the very last sharpness is gone—even in sibilant tracks.
Spatiality and separation remain preserved compared to the original cable, so they are roughly at the same level.
64 Audio U4s
My impression continues with the U4s: The Fusion 1 adds volume to the overall sound and a touch of warmth—which the U4s does not necessarily need, as it is already a rather warm-tuned IEM by default.
The virtues of the other two Horizon cables can, of course, also be brought out by the Fusion 1; additionally, it makes the voices on the U4s sound a bit more natural.
But here, compared to the Kronos, the limits of the U4s become very clear, because the Fusion 1 is capable of so much more. Additionally, the Fusion 1 as an upgrade option would double the base price of the U4s.
I recommend one of the other two cables for the U4s. Even the Code 23 MKII turns the U4s into a completely new IEM and almost fully utilizes its existing potential. The Code 24 MKII even "lifts" the U4s into a new class.
Who/what is the Fusion 1 (2025) suitable for?
The new Fusion 1 is suitable for upper mid-range IEMs (>CHF 2000), but many flagship IEMs can also definitely benefit from it. At 1199 CHF, it is a serious investment, but one that can be justified if your own "favorite IEM" does not reach its potential with the standard cable and you might even catapult it into a higher class.
Especially if you want to add fullness and volume to the sound and/or reduce possible harshness, the Fusion 1 is an excellent choice that is worth the money.
Considering additionally that the prices for the most expensive flagship cables now match or even exceed those of the most expensive IEMs, the Fusion 1 is more than a viable option.
Conclusion
All three new cables of the Horizon Series from Effect Audio offer excellent sound quality in their respective price ranges and can represent a meaningful and significant upgrade for your IEMs—unless a very, very good cable is already included, which unfortunately is often reserved for only a few flagship IEMs.
As always, the best thing is, of course, to test the cables at home with your own IEMs. However, the blog should already give a (hopefully) good impression of what you can expect from the new Horizon Series cables.
