ISN Audio Rambo II Review








ISN Rambo II Earbud Review



ISN Audio is a relative new Chinese brand that is producing portable audio gears like Earbuds, In-Ear Monitors and Cables. The Rambo II is the second earbud of the company that features 14mm diameter dynamic driver and a detachable cable that you can connect to the earbud monitor via MMCX connectors.




I would like to thank ISN Audio for providing me the Rambo II earbud 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 ISN Audio Rambo II is available on Penon Audio for 69,00 USD under the link below:




Package and Accessories:

The ISN Audio Rambo II came in a in a small rectangular cardboard box that features illustration and product brandings same like all ISN Audio product that I have reviewed before.

This box is contains the following items/accessories: 

  • 1 pair x ISN Audio Rambo II earbuds
  • 1 piece x Detachable cable with MMCX connector
  • 3 pairs x Open-back foams
  • 3 pairs x Closed-back foams
  • 1 piece x Shirt Clip
  • 1 piece x Zipper Case
  • 1 piece x Karabiner



Design, Fit and Build Quality:

The ISN Audio offers with the new Rambo II earbud a product with a solid metal shell in black color with a unique design compared to other earbuds on the market. The overall build quality of the earbuds is ageless!

On the front of the earbud is the earpiece with a fairly open grid design. The 14mm diameter dynamic drive which has diaphragm with a metallic color looks gorgeous under the grid.

The rear side of the earpiece has 3 (three) openings in the form of a slot.

At the rear side of the earbud shell is a protruding part that sports the ISN branding in white color.

Here is also the MMCX female connector that offers a tight fit.

The ISN Audio Rambo II comes with a detachable cable that features MMCX connector.

The connectors have metal housings in black color and have Left (L) & Right (R) markings in white color.

Each MMCX connector comes with an O-ring for extra protection and better seal.

The cable of the ISN Audio Rambo II has a non-microphonic insulation in black color.

The cable sports a plastic chin slider and a metal Y splitter.

The ISN Audio Rambo has a straight profiled headphone jack with a 3.5mm single ended connector and a metal housing in black color.

The earbud is slightly heavier compared to earbuds with a plastic shell, while it fits pretty well to my average sized areas.





Some Technical Specifications:
  • Model              : Rambo II
  • Unit                 : 14mm dynamic driver
  • Impedance      : 32 ohm
  • Freq. resp.      : 12Hz ~ 35000Hz
  • Sensitivity       : 113dB + -1dB @1kHz
  • Connector       : MMCX
  • Length             : 1.2m
  • Plug                : 3.5mm



Equipment’s used for this review:
  • IEM’s              : ISN Audio Rambo II, Ourart ACG
  • Source           : Hidizs AP80 CU, FiiO M3 Pro



Albums & tracks used for this review:
  • Fazıl Say – Nazım Oratoryosu (Live) (Flac 16bit/44.1kHz)
  • Vivaldi – Le QuarttroStagioni “The Four Season” (Tidal Hi-Fi)
  • Otto Liebert& Luna Negra – The River (Spotify)
  • Armin Van Buuren – Vini Vici (Spotify)
  • Lorde – Royal (Flac 24bit/48kHz)
  • Massive Attack – Angel (Flac 24bit/192kHz)
  • Portishead – The Hidden Camera (MP3 320kHz)
  • Metallica – Sad but True (Flac 24bit/96kHz)
  • Megadeth – Sweating Bullets (Tidal Hi-Fi)
  • Rush’s – Leave That Thing Alone (Flac 16bit/44.1kHz)
  • Slayer – Angel of Death (Spotify)
  • Tom Player – Resonace Theory “Album” (Tidal Hi-Fi)
  • Liquid Tension Experiment 2 – Acid Rain (Spotify)
  • Edith Piaf – Non Je Ne Regrette Rien (Flac 24bit/48kHz)
  • Sertap Erener – Aşk (Spotify)
  • London Grammar – Interlud (Live) (Flac 24bit/44kHz)
  • Laura Pergolizzi – Lost On You “Live at Harvard and Stone” (Tidal Hi-Fi)
  • Leonard Cohen – You Wnt it Darker (Spotify)
  • Dave Gahan – Kingdom (Tidal Hi-Fi)
  • Eric Clapton – Wonderful Tonight True (Flac 24bit/96kHz)
  • Chopin – Nocturn No. 20 In C-Sharp Minor (Flac 16bit/44.1kHz)






The Sound:

ISN Audio offers with the Rambo II an earbud with a very natural presentation that shows a slightly warmer than neutral tonality. The lower frequency region is well textured and has a moderate intensity, the midrange is pretty clear and lively, while the treble region shows a good level of extension and airiness.


Please note that my opinions bellow are based on a sound performance of an earbuds that do offer a quite different sound experience compared to IEM’s or Headphones. The sound performance of earbuds vary from user to user as the fit and ear anatomy greatly affects the overall experience.




The ISN Audio Rambo II has a pretty linear bass response with a pretty fast, detailed, and controlled presentation, while the extension and depth is in general a bit short. Especially remarkable is the overall separation and speed of the lower frequency region of the Rambo II.

The bass of the Rambo II should be enough for an earbud for genres such like Pop, Jazz, Metal, Blues or Acoustic music, while it could have more depth, rumble and intensity for genres like Trance, EDM or RnB.

The midbass region of the ISN Audio Rambo II is lightly pronounced, controlled and fast in its presentation, without to show no negative situations like a muddiness or unwanted mixings. The midbass shows more emphasis and quantity compared to the subbass which is a general situation for earbuds, while the slam effect of the midbass is on a moderate level for an earbud.



The ISN Audio Rambo II offers a very lively midrange with a pretty transparent and detailed presentation. The tonality is slightly bright and fairly neutral without to sound dry or dull.

Male vocals do sound quite vivid and clear, with the right amount of fullness. Female vocals on the other hand are very transparent, detailed and airy in its presentation, with good extension and control. Those who love to listen to vocals will love the presentation of the Rambo II.

The instrument tonality of the ISN Audio Rambo is neither thin nor too thick in tits presentation. Instruments such like guitars are slightly bright and showing good extension. Other instruments like flutes or violins are detailed and pronounced, while the general timber of instruments is distinct and clear.



Upper Midrange and Treble:

The ISN Audio Rambo II has a fairly strong upper midrange emphasis while the tonality is fairly neutral. This region gives a good amount of airiness and transparency to the overall presentation. The transition to the treble region are controlled without to show any remarkable sibilance or harshness.

The treble presentation of the Rambo II shows a distinctive, airy and well-extended tuning which doesn’t sounds too sharp. The treble quantity, intensity and sparkle is well balanced and sounds in general fast and controlled. Instruments such like crash cymbals are tight and showing good extension, while Hi-Hats are slightly in the background.


Soundstage & Imaging:

The ISN Audio Rambo II offers a spacious and airy soundstage presentation with a nice “out of the head” effect that I really enjoyed. The soundstage shows more width compared to its depth that is otherwise pretty good in earbud standards. The ISN Audio Rambo II is also successful in terms imaging with a good separation between the right and the left channels and positioning of vocals and instruments.




ISN Audio Rambo II versus Ourart ACG

The ISN Audio Rambo II shows a more natural and brighter tonality compared to the Ourart ACG which has a warmer and fuller tonality. The Ourart ACG has more subbass intensity and depth compared to the more linear character of the ISN Audio Rambo II.

The Rambo II shows slightly less midbass impact and extension compared to the Ourart ACG earbud, while it is superior in terms of control and resolution.

The midrange of ISN Audio Rambo II has a brighter tonality with a higher level of airiness and transparency. The male vocal presentation of the Ourart ACG shows more depth and fullness, while the ISN Audio Rambo II has the upper hand in terms of female vocals that do sound more realistic, crisp and lively.

The ISN Audio Rambo II has the upper hand in terms of upper midrange and treble extension and detail retrieval, while both are pretty controlled in this area. The Ourart ACG has a shorter extension with less sparkle and airiness on the top end, while it is quite ideal for longer listening periods.

Both earbuds are quite successful earbuds in terms separation and placement of instruments and vocals. The ISN Audio Rambo II shows a more spacious and airy soundstage presentation with slightly more wideness and depth.




The ISN Audio Rambo II is a very good earbud option for those who do give great value for balance, detail and clarity of the sound and love to listen to vocals. The Rambo II offers also in addition to the already good sound performance the ability to upgrade the cable to your liking via the MMCX connector.



Pros and Cons:
  • + Balanced & Natural Presentation
  • + Bass Control and Speed
  • + Midrange Clarity and Detail
  • + Treble Extension
  • + MMCX Connector & Build Quality
  • – Subbass Depth & Extension
  • – The Box is A bit too Minimalistic








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2 Responses

  1. Khalid says:

    Loved the review! I was looking to purchase this but wanted to compare this to the Penon BS1 Official.

    I understand that they are in a different price range, but objectively, which one is better to you? I also wanted to know about the fitment of both of those, I’ve seen other reviews talking about the fitment of these, and I have had earbuds which were not very nice to use due to the fitment, such as the tomahawk mrz earbud.

    I had a shozy cygnus in the past as well and was wondering if you had any experience with that as well?

    • Gökhan AYDIN says:

      Thank you very much for your kindness. The Penon BS1 Official is definitely better in terms of overall sound performance while the Rambo II offers a better fit. The cable of the BS1 Official is a bit heavy.

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