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Fidue Sirius A91 IEM - Every Dog Has His Day

"What genre is the Sirius not good for? We haven't heard anything which the Sirius cannot do justice to."

Fidue Sirius A91 IEM - Every Dog Has His Day



It's always nice to see a brand bringing out a new flagship model, and Fidue are certainly looking at the stars with the Sirius. Boasting a driver configuration consisting of 4 custom-made balanced armatures and one dynamic driver for the bass frequencies, Sirius promises to illuminate us; but is it a magnitude better than the competition?



  • Lovely presentation
  • Strong carry case
  • 2.5mm balanced cable as standard
  • Adaptors for use with 3.5mm sockets
  • removable cable locks into place



  • Carry case is a bit bulky - that's all!


fidue sirius a91


Design and appearance

This is certainly one of the best presented IEMs; the capsules themselves are very strong and the cable is a fabric coated effort which is quite reminiscent of a full size flagship cable. This is terminated with a 2.5mm balanced jack as standard, for use with Astell&Kern palyers or the Lotoo PAW 5000 for example; more are sure to follow. However if you are still languishing in the world of 3.5mm sockets then adaptors are included; one for a standard 3-pole stereo socket and another 4-pole for better compatibility with some 4-pole sockets.


The case is similarly made well but it's quite chunky; it's probably designed to go into a bag rather than a pocket.


Durability & build quality

It appears that no expense has been spared in terms of materials used; it's all very sturdy and gives the impression that it'll go on for years. Strain reliefs are good and as mentioned above, the cable is thick and luxurious without being cumbersome. It behaves itself nicely.


The cable is removable and the MMCX connectors are kept in place using locking rings, which also take the strain. It's still possible to rotate the capsules with the cable locked into position, so a good fit is always easy to achieve.



Like the case, the capsules are on the chunky side but they sit in place quite comfortably without sticking out. The fabric cable also helps to fool us into thinking we aren't wearing earphones at all, and the sound of the Sirius enhances this feeling (more on the sound below)!


Sound isolation

Isolation is decent enough; this is of course dependent on the sort of seal which can be achieved with the supplied eartips. This may be improved with the Comply eartips which are also included. Exterior noise tends to vanish when the play button is pressed, especially when music sounds as it does from the Sirius!


Sound characteristics

The sound of the Fidue Sirius sits together so nicely, it's a challenge to pick out the features of the bass, midrange and treble. It's a tangible and cohesive presentation which lets us know that this earphone is not playing around. Other flagship IEMs might emphasise detail which makes them a touch bright, or there may be a smoothness there in which something seems to be lacking. The Sirius sits perfectly between the two camps, giving up details effortlessly with an ease which cajoles the brain into accepting what it's hearing as real.



Bass is tight and authoritative with a rich creamyness which really appeals. Definition is very good, with shaking drumskins and similar low-frequency details nicely rendered. Sub bass is there in quantity when needed, and it's nicely balanced with the rest of the presentation so it never threatens to take over.



Midrange frequencies are about as present as they can be without risk of fatigue; they're clear and vibrant with no hard edges. Older recordings get a new lease of life as if they're brought up to date. It's a bit odd, but a very nice type of odd. Steppenwolf's 'Magic Carpet Ride' could have been produced last week, and the Temperance Seven's renditions of 1920s dance music are so fresh, it seems a real possibility that a flying champagne cork might assault us. Newer, well produced/mastered music needs to be heard to be believed!


There's a good amount of space and things never seem to get bogged down with a lot going on in the music. Reverbs and harmonics are clear and give a tremendous sense of being there and directly involved with the music.



Up top, higher-frequency detail is similarly treated with a bright-sounding presence which knows just when to back off. It has a natural and organic quality to it, with a shimmery lushness which gives another touch of realism to the presentation. The Sirius is exceptionally revealing but never strays beyond the bounds of believability.


fidue sirius a91 accessories


Soundstage & Separation

Soundstage is very impressive; the head is surrounded by music, helped along by the Sirius' very open sound. Instruments are easy to pick out and have great definition, but at the same time everything sits together very well should you just wish to relax and take it all in.


Music Genres Good For and Why

What genres is the Sirius not good for? We haven't heard anything which the Sirius cannot do justice to. It shines with everything.


If you are looking to upgrade, you could do a lot worse than giving the Fidue Sirius a try. It is utterly deserving of its flagship status and it's been a real pleasure to review. It's one of those earphones which will have you tearing through your music collection in order to hear everything for the first time, again!


Fidue Sirius A9Video Review

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2 thoughts on “Fidue Sirius A91 IEM - Every Dog Has His Day”

  • Athos

    Could you tell how the sound of A91 compares to Fidue A83 or other iems?

    • Steve

      Hello, I reviewed the A83 here -

      It's hard to compare the two models as the A91 I reviewed is with another reviewer so I cannot try it right now. However the A91 is clearly better - there's a solid yet effortless quality to the A91 where the A83 works a bit harder. Other flagship IEMs tend to emphasise the treble in the sound to accentuate the detail but the A91 is smooth yet detailed and very competent-sounding too.

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