Not just numbers: Effect Audio Fusion 1 and Code 23 

Sound impressions

I’ve been testing Fusion 1 and Code 23 for the past month with a variety of IEMs across a large music library, and in that time I’ve come to better understand what effect each of these very special cables have on what I’m hearing.

If you’ve read my previous cables reviews, you’ll know that I don’t consider cables to have their own ‘sound’, but rather their construction, material, shielding, and conductive properties affect the FR balance of different IEMs in different ways. Also, the overall change a cable makes as part of the chain is relatively small, in my opinion, in the order of single digits if I were to guess a number, so even the very best cables (with very few exceptions) are going to be little more than a tweak in the grand scheme of things.

With all that said, let me try articulate what I’m hearing with each of these cables, and I’ll do so by describing the effect they have with the IEMs I typically use.

FIR Audio Xe6 (reviewed here). Xe6 is an exciting IEM with a warm colouration epitomised by significantly elevated midbass and lower midrange in its stock tuning. 

Fusion 1 tightens the bass somewhat, mildly reducing quantity but improving clarity as a result of a smoother shift between lower and upper mids. Treble is kept sparkly and clean, without much attenuation to quantity, while stage and resolution are both given a boost. 

With Code 23, I’m hearing an even more powerful and emotive bass presentation, with a lift in sub-bass improving the balance between sub and midbass. Lower mids are tightened slightly, though the midrange in general is left intact, maintaining its natural warmth and glow. Treble is likewise kept relatively intact, though I’m hearing it slightly smoother when compared to how it plays with Fusion 1. Overall, the sound is bolder and more direct, with a deeper stage.

Code 23 is my preferred pairing for Xe6, with more impact and punch, and added warmth and weight down low without losing treble detail or clarity. It feels like a thicker version of the stock Rn6 cable, which, like Code 23, happens to be more suited to Xe6 in my opinion.  

FIR Audio Rn6 (reviewed here). A limited-edition IEM using the same driver configuration as Xe6 but with a very different tuning, Rn6 is more balanced and favours clarity over warmth. 

Fusion 1 gives Rn6 a slight boost in the lower ranges, especially midbass, filling out some of the ‘hole’ between sub and upper bass frequencies. Its resolution boost is also apparent, with a slight lift in the midrange frequencies and added sparkle in the treble, all the while managing to shave off some errant peaks up top. Fusion 1 also adds some depth to the stage, mostly evident in echo decay. 

Code 23 gives Rn6 a warmer sheen without veiling any of the midrange frequencies. The weight that it adds is balanced out by a clear treble response that somehow sounds even more extended and airy, an unusual trait for a solid copper cable. The bolder sound does impact stage size slightly, though the effect isn’t always obvious with most music. 

Fusion 1 is my preferred pairing with Rn6, improving on its already excellent technical performance while maintaining a slightly warm, smooth but clear and extended sound across the FR. The visual synergy with my custom Rn6 is also sublime.   

Campfire Audio Trifecta (reviewed here). A divisive IEM for many, with a big, bold sound, rich and powerful bass response, naturally warm timbre, and realistic though occasionally wild and biting treble. 

Fusion 1 straddles Trifecta’s best qualities and improves on them, tightening up its midbass while infusing it with even more texture and control. It also adds some speed to the mix, with faster decay, though Trifecta’s inherently slow drivers will never sound particularly speedy. There’s also some tweaking to the treble peaks going on, which helps smoothen the treble response and open up the stage beyond its already sizeable proportions.  

Code 23 is basically bold on bold. While I do hear some refinement across the board, especially in the upper frequencies, the sheer richness of Trifecta’s sound combined with the richness of Code 23’s copper personality is perhaps too much of a good thing. It definitely doubles down on Trifecta’s organic tonality, and sharpens up its technical ability just enough to notice, especially with modern music.

Fusion 1 is my preferred pairing with Trifecta, giving it a more refined presentation and taming some of its wilder tendencies. Ergonomically I also prefer Fusion 1 with Trifecta’s featherlight shells.   

Campfire Audio Bonneville (reviewed here). I haven’t had as much time to listen to Campfire’s new Chromatic Series flagship, but this balanced yet slightly bold and always engaging IEM is really growing on me.

Fusion 1 gives Bonneville even more balance, tightening up an already-tight bass response while gently lifting the midbass just so. Midrange notes are played with added weight, and the jump up in resolution is notable. So is the improvement to stage dimensions, with finer sounds more audible in the left and right extremes. Treble remains smooth, with maybe a touch of added sparkle from the silvery gold cable. 

Code 23 gives Bonneville an altogether bolder, more direct sound. Bass notes are audibly lifted in volume and weight, and there’s a better sense of rumble and texture down low too. Midrange, while not quite as resolving as I hear it with Fusion 1, is still very clear, as this is Bonneville’s inherent strength. There’s some smoothing in the treble, but it doesn’t negatively impact stage size or other technical performance metrics to my ears. 

It’s a difficult call to pick a favourite pairing here, as both Fusion 1 and Code 23 give Bonneville’s sound a charismatic facelift. I like Fusion 1’s refinement and technical excellence as much as I enjoy Code 23’s warm, weighty sound that doesn’t sacrifice clarity or balance.    

FatFreq Maestro SE (reviewed here). An enigma of an IEM when the music is rich with sub-bass, Maestro SE is actually a very balanced and technically-impressive IEM in its own right, despite its reputation as a bass monster. 

Fusion 1 does nothing to change my opinion of MSE, that being that it’s ultimately a balanced monitor with a fun, direct sound and very few tonal quirks. There’s some midbass lift with Fusion 1 that actually benefits MSE’s overall balance, and when the sub-bass kicks I, I hear it as more controlled with slightly less rumble. Resolution is on par, which is to say excellent, and stage is slightly improved too, though MSE’s stage is not spectacular to start with. 

Code 23 plays on MSE’s bassy personality traits, adding a dose of midbass warmth and even more sub-bass rumble when called for. Midrange notes benefit as a result, while treble is smoothed over just enough to negate any peakiness typically caused by improper fit. There’s a richness to the sound that really improves the overall presentation, and if you can live with the size of the cable and IEMs combined, it could prove an absolute winner as an upgrade from stock. 

Code 23 is an easy choice for me with MSE, although technical listeners will likely see it the other way and pick Fusion 1. 

Continue to closing thoughts…



Picture of Guy Lerner

Guy Lerner

An avid photographer and writer 'in real life', Guy's passion for music and technology created the perfect storm for his love of portable audio. When he's not playing with the latest and greatest head-fi gear, he prefers to spend time away from the hobby with his two (almost) grown kids and wife in the breathtaking city of Cape Town, and traveling around his native South Africa.


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