FOSI IM4 REVIEW

>>I am brazilian and I speak portuguese, so forgive my english, I’ll use translation tools to help<<


INTRO:

After reviewing the FOSI DS3 DAC/AMP dongle, it’s now time for the in-ear earphones, the FOSI IM4. These IEM stand out for their minimalist aesthetic and high-quality construction. So far, this is the first in-ear earphone I’ve seen FOSI manufacture… I may be mistaken if they’ve made others in the past.

Price: $99.99 USD
Color: Black (Obsidian) or Silver (Galaxy)
Cable: 3.5mm with Mic.

FOSI review: DS3.



FOSI LINKS:

https://amzn.to/4uZp38X (US)

https://amzn.to/3PDk3qB (UK)

https://amzn.to/4cf7udN (DE)

https://amzn.to/4m0SWSd (FR)

https://amzn.to/4c11Meh (JP)

https://s.click.aliexpress.com/e/_c3xxoN1F (PC)

https://s.click.aliexpress.com/e/_c3wlHQ5J (APP)



SPECIFICATIONS:

Single DD:

  • (1) 10mm beryllium coated Dynamic Driver per side

– Effective frequency: 20Hz – 20kHz
– Impedance: 21Ω
– Sensitivity: 109dB
– THD: <1%
– Connectors: 2pin 0.78mm (detachable)
– Cable Plug: 3.5mm SE (straight design)
– Cable size: 1.20m
– Cable material: 5N OFC Silver-plated Copper Cable
– Shell: 6063 CNC Aluminum Alloy
– IEM weight: 6.4g (one side)(without eartips)
– Cable weight: 23.6g
– Total weight (packaging, iems, etc): 280g
– Packaging size: 17.5cm [H] x 12.7cm [W] x 5.7cm [D]


UNBOXING:




PHYSICAL ASPECTS:

Construction:

  • Excellent build quality.
  • Quality that’s worth more than the price (subjective).
  • Made of aviation-grade aluminum.
  • Minimalist aesthetic (I really like it).
  • Open-back design.
  • Removable nozzles.
  • Features 2 vents.
  • Good carrying case, although basic.
  • Interesting unboxing, it’s a good kit for the price.


Eartips:

  • 3 types of eartips: Balanced, Bass, Deep Bass.
  • 3 pairs in sizes S/M/L.
  • The Balanced eartip is wide bore.
  • I found the variety of tips good.
  • I confess they are generic tips, but functional.
  • Standard size, if you wear M, then it’s M.
  • It’s possible to find the ideal sound with the stock eartips (subjective).
  • I don’t see the need to acquire other eartips (subjective).
  • I did the review with the Deep Bass eartip (size M).


Cable:

  • High-quality cable.
  • Very light and thin, and also beautiful.
  • Great malleability.
  • Doesn’t tangle.
  • Doesn’t develop “memory” (creases).
  • The earhooks are thin and comfortable.
  • No microphonics.
  • The chin slider works very well.
  • 2-pin 0.78mm connectors.
  • I see no need for replacement (subjective).


Fit and comfort:

  • Vertical fit. Great stability.
  • Very comfortable. Great ergonomics.
  • The skin contact is very soft.
  • Good shape for all ears.
  • Medium insertion.
  • Good isolation.
  • 6.4g is still a good weight for an IEM.


Earphone kit (accessories):

  • IM4 earphones.
  • 3 types of ear tips (9 pairs).
  • 3.5mm cable.
  • 1 extra pair of filters.
  • Carrying case.
  • Manual and guide.






SOUND ASPECTS:

Sound:

  • Forward, fun, and lively sound.
  • V-shaped tuning with a slight emphasis on the upper-mids.
  • Somewhat reminiscent of the Harman Target.
  • More prominent bass and upper-mids, linear treble.
  • The definition is good.
  • The detail is also good.
  • It can be considered an IEM with a certain balance.
  • Rock and Hard Rock were two genres that sounded very good.
  • If you listen to music very loudly, be aware that the pinna gain can be tiring (subjective).
  • The open-back design didn’t alter the sound (in my opinion).
  • There is indeed sound output through the opening, but for me it only created “leakage”.


Bass:

– Quantitative:

  • Moderate to high bass frequencies.
  • Not for bassheads.
  • Although the bass here doesn’t disappoint.
  • I like bass and I really enjoyed the IM4 bass.
  • Sub-bass and mid-bass with great presence.
  • Both regions stand out linearly.
  • Great balance between sub-bass and mid-bass.

– Qualitative:

  • Full, strong, authoritative, fast, and warm bass.
  • Great texture and physicality.
  • The extension is very good. There’s no roll-off.
  • Bass that brings a dose of fun and versatility.
  • The definition is very good.
  • The impact is very audible and “tight”.
  • They don’t invade the mids.
  • Bass that combines well with various musical genres.
  • They aren’t boomy, not bloated, not muddy.
  • Not for Bassheads but it’s good to EDM, Reggae, Rock, Hip-Hop, etc.
  • For me, the bass is the best part of the IEM.


Mids:

– Quantitative and qualitative:

  • The mid/upper-mids are “forward.”
  • These frequencies are closer to you.
  • Pinna gain with a certain emphasis.
  • Although “forward,” I didn’t feel harshness or aggressiveness.
  • I’m not a big fan of “forward” upper-mids, but I could hear them.
  • I listen to music at lower volumes.
  • If you listen at very high volumes, be aware of fatigue (subjective).
  • The definition is very good.
  • Great clarity and transparency.
  • Good airiness and detail.
  • This upper-mids region has a cold touch.
  • Guitars and vocals stand out well.
  • Wind instruments have great energy, the sound is more “frontal.”


Voices:

  • Good for both types of voices (low or high).
  • High/female voices performed slightly better.
  • “Forward” IEM deliver more clarity and vitality for high-pitched tones.
  • “Rolling in the Deep – Adele” has great clarity and projection.
  • Fortunately, lower voices also performed well.
  • IEM that render various voice types very well.


Treble:

– Quantitative:

  • Moderate treble frequencies.
  • To me, they sounded neutral.
  • It was the least prominent frequency in the IEM.
  • I didn’t experience fatigue because of the treble.
  • Not for trebleheads.
  • Suitable even for those with sensitivity in that region.
  • Discreet treble because the upper-mids are more prominent.

– Qualitative:

  • Linear, controlled, comfortable and of good extension.
  • Natural/normal sparkle.
  • Good detail and airiness.
  • Good level of definition.
  • Not shrill, not sharp, not harsh.
  • I didn’t experience sibilance, coloration, or peaks.
  • Hi-hats have good resolution, without harshness.
  • Ride cymbals sound natural.


Soundstage:

  • I found the soundstage to be good.
  • Good spatiality, but nothing beyond the standard.
  • Good width and height. Average depth.
  • V-shaped IEMs generally have a good soundstage.


Imaging:

  • I found the instrumental separation to be good.
  • The stereo image is also good.
  • Hybrid IEMs have an advantage (this isn’t a rule).
  • The Hexa and EM6L are better in this regard.


Detachable filters:

  • I tested the IEM with the black filter.
  • I only felt a slight emphasis on the upper-mids (with the golden nozzle).
  • In my opinion, the black filter is the best.
  • I think changing the eartips has more influence on the sound.


Driver flex test:

  • The IM4 didn’t have Driver Flex characteristics.


Amplification:

  • Easy to push.
  • Doesn’t need a powerful amplifier.
  • A DAC/AMP dongle is sufficient.
  • I review the IM4 with the FOSI DS3.
  • I only used the 3.5mm output.
  • DS3 at Max (60 steps) and 20-30% (100 available on the W10).



PROS AND CONS:

– Good value for money
– Aesthetically pleasing (subjective)
– Excellent build quality
– Forward sound
– V-Shape tuning
– Good resolution level
– Good soundstage
– Good imaging
– Easy to push
– Comfortable to use
– Great fit
– Good for all ear types
– Good for long listening sessions
– Great cable
– Variety of eartips
– Good carrying case

– Upper-mids beyond I like (subjective)
– Filters don’t alter the sound as much as eartips
– Open-back didn’t make difference in sound
– Sound leakage to the outside



GRAPHS BY SUPER*REVIEWS:






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