ISN Audio S4 Upgrade Cable Review







ISN Audio S4 Upgrade Cable Review



ISN Audio is a Chinese brand that is producing earbuds and cables for In-Ear Monitors.

The ISN Audio S4 which I will know review is a 4 core Sliver-plated upgrade cable with 63 strands and 252 wire conductors in total.


ISN Audio Official Website:



I would like to thank ISN Audio for providing me this sample via Penon Audio for review purposes. I am not affiliated with ISN Audio and Penon Audio beyond this review and these words reflect my true and unaltered opinions about the product.



The Price:

The ISN Audio S4 upgrade is available for 68,90 USD with MMCX and 2-Pin connectors. You have also the option to choose one of the 3.5mm unbalanced, 2.5mm balanced and 4.4mm Balanced (+1,00 USD) headphone jacks.

Purchase Link:



Package and Accessories:

The ISN Audio Rambo is coming in a small rectangular cardboard box that features the product branding.

The box is containing the following items:

  • 1 pcs x ISN Audio S4 upgrade cable



Technical Specifications:

  • Material          : Silver Plated OCC wire (Single Crystal Copper)
  • Cores              : 4 Cores
  • Strands           : 63 Strands
  • Conductors     : 252 Conductor Wires
  • Interface         : MMCX or 2PIN 0.78mm
  • Plug                : 3.5mm Unbalanced, 2.5mm Balanced and 4.4mm Balanced
  • Cable  Length : 1.2m

Design and Build Quality:

The ISN Audio S4 is a Silver Plated OCC (Single Crystal Cooper) Cable with a nice braided design. The cable is made of 4 cores and each core has 63 strands which makes 252 conductor wires in total. The length of the cable is approx 120cm and shows a good craftsmanship.

The ISN Audio S4 is available in two connector options, which are the MMCX (Micro Miniature Coaxial) and the 2-Pin (0.78mm) variant with male connectors.

The cable has a soft transparent plastic insulation which shows a micro-phonic effect on an acceptable level.

The MMCX/2-Pin connectors are protected by the black metal housings with left/right indicators (white for left and red for right). The ISN Audio S4 has also heat-shrink ear guides for a better over the ear wearing experience.

The ISN Audio S4 features a nice metal y-splitter with carbon fiber pattern and a circular slider in black color.

The headphone jack is straight profiled and has a stylish looking housing with carbon fiber effect. The headphone plug is available in the 3.5mm unbalanced, 2.5mm balanced (TRRS) and 4.4mm balanced variants.



Equipments used for this review:

  • Cables            : ISN Audio S4 Silver Plated OCC cable
  • IEM’s              : FiiO FH5, Final Audio E4000,
  • DAP/DAC’s    : iBasso DX220, QLS QA360, xDuuo XD10 Poke



Albums & tracks used for this review:

  • Gogo Penguin – Raven (Flac 24bit/192kHz)
  • Otto Liebert& Luna Negra – The River (DSF) – Binaural Recording
  • Vivaldi – Le QuarttroStagioni “The Four Season” (Wav 24bit/88kHz)
  • Elton John – Your Song (Flac 24bit/192kHz)
  • David Bowie – Black Star (Flac 24bit/96kHz)
  • Dave Gahan – Kingdom (Flac 16bit/44.1kHz)
  • Eric Clapton – Unplugged Album (Flac 24bit/96kHz)
  • B.B. King – Riding With The King (Flac 24bit/96kHz)
  • First Aid Kit – My Silver Lining (Flac 16bit/44.1kHz)
  • London Grammar – Interlude (Live) (Flac 24bit/88kHz)
  • Aretha Franklin – I Say a Little Prayer (Wav 16bit/44.1kHz)
  • Diana Krall – So Wonderful (DSF)
  • Laura Pergolizzi – Lost On You “Live at Harvard and Stone” (Wav 16bit/44.1kHz)
  • Rush’s – Leave That Thing Alone (Flac 16bit/44.1kHz)
  • Liquid Tension Experiment 2 – Acid Rain (Flac 16bit/44.1kHz)
  • Opeth – Damnation (Wav 16bit/44kHz)
  • Metallica – Sad but True (Flac 24bit/96kHz)
  • Megadeth – Sweating Bullets (Flac 24bit/96kHz)
  • Slayer – Angel of Death (Flac 24bit/96kHz)
  • Armin Van Buuren – Vini Vici (Spotify)
  • Lorde – Royal (Flac 24bit/48kHz)
  • Tom Player – Resonace Theory (16bit/44.1kHz)
  • Massive Attack – Angel (Flac 24bit/192kHz)
  • Portishead – The Hidden Camera (MP3 320kHz)





The Sound:

I have tested the ISN Audio S4 upgrade cable with the FiiO FH5 and Final Audio E4000 and want to share now my impressions for this cable in terms of changes/improvements compared to the stock cables of those IEMs.


Bass / Midrange / Treble:

The Final Audio E4000 and FiiO FH5 shows better subbass depth, extension and control with the ISN Audio S4 combination compared to their stock cables, while the difference in terms of subbass speed still unchanged.

When it comes to the midbass region, the ISN Audio S4 is adding slightly more fullness compared to the stock IEM cables I have listened during this review. This is especially pleasing for instruments such as the contrabass and the bass guitar.

There is a slightly increase of clarity and airiness of the overall midrange presentation, especially compared to those of the Final Audio E4000’s stock cable. The lower midrange of the both FH5 and E4000 showing an increase of body and depth which is a good benefit for the male vocals, while the upper midrange sounds slightly more controlled and smooth compared to stock cables of both IEM’s.

There is also some increase of detail retrieval compared to the stock cable of the Final Audio E4000.

The ISN Audio S4 upgrade cable shows some additional micro detail retrieval and extension in the treble range of the Final Audio E4000 and FiiO FH5 compared to their stock cables. There is also a slightly increase in treble quantity which was noticeable while listening to instruments such like pianos, cymbals or violins. The treble range sounds a tad fuller as well without being sharp or sibilant.



The ISN Audio S4 is adding slightly more width to the soundstage compared to the stock cable of the Final Audio E4000 and FiiO FH5, while there is no remarkable difference in terms of soundstage depth. In addition, the ISN Audio S4 cable has achieved better instrument separation and transparency with both IEM’s.



The ISN Audio S4 is an affordable upgrade cable is able to improve the sound performance of your In-Ear Monitors. The bass sounds slightly more controlled and has better extension, while the midrange shows higher clarity, and the treble range better extension and micro detail.



Pros and Cons:

  • + Bass control and extension
  • + Improvements of clarity and micro detail
  • + Good Build Quality


  • – No protective case included


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