A cup of basil tea and some favorite BLUES always rejuvenates me after a hectic day in office. I prefer Earbuds more than an IEM or Headphone, when my body is totally exhausted and crying only for the bed. So as of now I have collected more than twenty Earbuds and use them periodically. Today for review I got the ISN Audio Rambo from Penon Aduio and after using it almost a month writing this review. The unit completed almost 100 hours of controversial burn-in and I have used normal thin foam for this review. Dount foams are not suitable with Rambo.

ISN Audio Rambo

Buying Link – https://penonaudio.com/isn-audio-rambo.html


  • Driver Size – 14.8mm,
  • Shell – Yuin,
  • Frequency – 6-25KHz,
  • Impedance – 32Ω
  • Sensitivity -115dB,
  • Plug Type – 3.5mm/2.5mm.
  • Cable Length: 1.2m.

What’s inside the Box ?

  • Rambo Earbud,
  • 6 pairs of Eartips,
  • Shirt Clip,
  • Metal Carabiner Clip Snap Hook Key Ring,
  • Velcro cable tie,
  • 1 durable Carry case.
ISN Audio Rambo


Rambo needs good amount of power to shine. As per specification its 32 Ω and sensitivity is -115dB still need powerful sources to open up. I have used my Fiio 1 mk2+ Topping NX3s, Fiio Q5 + Fiio A5, IFI XDSD as sources for this review.

Presentation, Design & Build Quality 

The presentation is simple. A 120cm X 75 cm cardboard box and inside that a hard earphone case. Brand name and specifications clearly printed on the box. Earbud and accessories securely packed inside that carry case. Rambo is a Hand crafted Earbud with Yuin shell, beautifully braided silver cable and matching non bulky 3.5 mm jack & Y splitter.

We know that Yuin shells are best in terms of fit and comfort. Thankfully ISN Audio has used a good quality Yuin shells here but I am concerned with the cable; it’s a bit softer side and may not last long after daily torture. The chin slider is small and a bit tight. Supplied hard case is very good in quality, so overall ISN Audio managed to maintain quality for their first Earbud.


Before proceeding to the sound part I want to clear a point i.e. the contradiction of name. Sylvester Stallone’s Rambo (John Rambo) is nothing to do with ISN Audio Rambo but the first impression may go to a buyer that this Earbus is for bass lovers which is actually opposite.

Sonically ISN Rambo is a bright sounding Earbud. But there is a catch, ISN Rambo proved how beautiful a bright sounding Earbud can be. Give Rambo at least 100 hours of burn in and let it rock and roll. 


Out of the box Rambo is a bit Bass shy but after burn-in it improved a lot, still quantity is not that much for a bass lover to appreciate. Surprisingly quality of lower frequency is at least good. Bass is tight, punchy and texture is there. Sub-bass region is not that emphasized and also Speed is not that fast and accurate.

For example in tracks like ‘Dreams’ by Fleetwood Mac and ‘Billie jean’ by M. Jackson you can feel the punch but slower decay also can easily noticed.


Now things going to change because Midrange is the strongest part of Rambo, midrange is definitely forwarded in Rambo. Upper Mids are more emphasized than lower Mids. Both male and female vocals are crisp, clear and full of texture. Midst are totally transparent, songs like ‘Bennie And The Jets’ by Elton John, ‘Talking To The Moon’ by Don Henley and ‘Don’t Let Me Be Misunderstood’ by Nina Simone sounds just natural and mesmerizing.


Treble is the cream of Rambo. Upper frequency part is well extended, clean, and airy; no noticeable harshness is there. With treble demanding tracks like ‘The chain’ by Fleetwood Mac the sparkle also can be noticed. Both quality and quantity is top notch. Personally didn’t expect such polished treble from Rambo but it managed to impress me.

ISN Audio Rambo

Soundstage & Imaging

Soundstage is very good in terms of width and depth, even better than some IEMS and headphones I have heard before. Imaging is above the average still managed to bring the imaginary stage with complex tracks.

ISN Audio Rambo


For 65$ I don’t think there is much to think before buying ISN Audio Rambo, unless you are a die heart bass fan. Sufficient Bass, clear Mids and sparkling Treble if this is your requirement then Rambo is a perfect one. For Jazz, blues, country music Rambo is one of the best Earbud I have heard till now but ‘Romeo’ could be a better name for it.

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7 thoughts on “ISN AUDIO RAMBO REVIEW”

  1. Very good review. Sort and simple..I want to ask two questions
    1. Trable competible for fast track.
    2. How is the sound of tabla, guitar (for bollywood 90s music)

    1. Thanks my friend, even with fast tracks Rambo performing very well. Tabla sounding good but as its lacks in bass, sound of Tabla feels slow. Guitar is just beautiful. Highly recommended for Bollywood 90s music as Rambo’s Mids are phenomenal.

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