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  1. Palash
    Roses, N'OT Guns
    Written by Palash
    Published Apr 5, 2019
    Pros - Good Build quality,
    Sweet Midrange,
    Sparkling Highs,
    Soundstage and Imaging,
    Cons - Cable could have been better,
    Bass shy.
    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.


    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.



    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.


    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.


    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.
      noknok23 and Otto Motor like this.
    1. View previous replies...
    2. Palash
      Thanks. I have already mentioned the sources earlier in this review. For comparison in this price point I have used only OUTART ACG. I will update this review with a comparison part soon .
      Palash, Apr 5, 2019
    3. Otto Motor
      Concise and to the point! I am about to open mine...
      Otto Motor, Apr 17, 2019 at 1:37 PM
      Palash likes this.
    4. Otto Motor
      I am not an earbud guy but...this one is really good: warm, good intimate mids, and the well extended treble you described. It also has a fantastic timbre....couldn't get enough of that Chopin cello sonata.
      Otto Motor, Apr 19, 2019 at 7:37 PM
      Palash likes this.