ISN Rambo English Review


This Charming Man




Construction and Design 75%
Adjustment/Ergonomics 85%
Accessories 70%
Bass 75%
Mids 85%
Treble 75%
Separation 80%
Soundstage 80%
Quality/Price 85%




  • Great balance between driver and capsule.
  • Balanced and natural sound.
  • Comfort.
  • Cable, plug.
  • Transport box.




  • Bass limited in extent and quantity.
  • Some lack of depth.


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Again another model of the ISN Audio brand. In this occasion it is about earbuds, of controversial name: Rambo. The least you can expect with such a combative name is battle, war … But really these earbuds are totally harmless, there is nothing that produces an ounce of aggressiveness in them, neither in their design nor in their sound. For this occasion, ISN has chosen to mount one of the classic capsules, but more comfortable on the market, the PK type. My experience tells me that many of the earbuds I own with this type of capsule have a tendency to offer a similar sound: an enhancement in the mid zone, from 250Hz to beyond 1kHz, with a predominance of male voices, soft basses and little prominence and sparkling highs. It’s also true that the rest of my earbuds of this type are cheaper. So, you have to see what Ios Rambo can offer, whose price is over 65$.





  • Brand: ISN Audio
  • Model: Rambo
  • Type of Drivers: Dynamic 14.8mm
  • Frequency response: 6Hz – 25kHz
  • Sensitivity: 115dB
  • Impedance: 32Ω
  • Jack Connector: Straight 3.5mm, gold plated.
  • Cable: 4 wires of 1.2m





The Rambo come in a box exactly like the C16 cable, sealed in transparent plastic, dimensions 122x78x38mm. In this case, the box does not have any transparency. On the top there is a black background sticker with the logo and the mark on the top. In the center, with eye-catching red letters, whose font simulates handwriting, the model name: Rambo. Below, a realistic photo of the earbuds and the cable.


After opening the box there is only a black, rigid box, with zipper, very suitable for storage and transport. Inside there is a Zip bag with 6 pairs of full foam, black. A clip for the clothes, a small violet musket and, finally, another zip bag containing the earbuds. The cable of the Rambo comes with a velcro tape.

The packaging is fully functional, simple, without boasts or luxuries. But it comes with everything you need, except donut foam.



Construction and Design


Describing an earbud that uses a capsule as classic as PK has little history, it can only be summarized in highlighting the details. And actually, these capsules offer several. The first detail is in the cover that encloses the driver. Usually it has a thinner and rounded profile, in this case it is wide and flat. The second detail is found in the horizontal rear openings: there are two notches, but only the top is open, the bottom is sealed.

I have a particular theory (although possibly more than one has also thought about it): I think there is a relationship between the sound/profile of earbuds, depending on the type of capsule used. The PK capsule has some limitations. Starting with the diameter, which restricts the use of larger drivers. There is also a limit in the depth, perhaps this reason has to do with the Rambo cover is wider, to gain something more in this sense. In the end, all these details influence the final sound.

Finally there’s the cable. The first impression it gives is that it is something fine and delicate. It consists of four braided wires, of small thickness, covered with transparent plastic, which shows a dark silvery material. But in the end the cable is very light and manageable, has very little tendency to get tangled and does not offer any microphones. On the other hand, there are the metal parts. Both the plug and the splitting piece are two almost identical black cylinders with a double notch ring, which makes them much easier to use and ergonomic. The plug has a thick piece of plastic, which protects the cable junction. The name of the brand is written on it. The connector is 3.5mm gold-plated Jack. The name of the model is written on the splitter. Finally, the cable has a small sphere with a through hole, which is used to adjust the cable under the chin.

In my opinion the cable is almost perfect for these earbuds, it does not weigh, it is not bundled, it is highly flexible, the connectors are comfortable, of great quality and ergonomics. In addition, it comes with a piece of adjustment. Everything I usually ask for.



Adjustment and Ergonomics


The PK capsule is one of my favorite capsules in terms of fit and ergonomics, its small diameter and its thin spike represent an achievement in design, between minimalism, simplicity and practicality. In this case, the detail I mentioned earlier, about the thickness of the cap, is the only thing that could be susceptible to limit the comfort of these capsules.

Another point that facilitates comfort is the cable. In this case, the fact that it is made up of four fine, braided threads is an advantage, because it is not binding, it has no rigidity at all, it is highly manageable, it is very easy to pick up. In addition, all the metallic pieces that compose it do not do more than to facilitate any task. The design of the plug, the splitter and the adjustment sphere form an excellent whole.







The ISN Rambo are warm but balanced earbuds. They have a rather neutral low zone, well balanced mids and a good spark of brightness at the top.





The low zone of the earbuds with a PK capsule I’ve always found conflictive. But the Rambo solve the problem better than the rest. The sub-bass below 40Hz is light, providing a moderately limited depth. From there its presence improves and rises, but to stay at a fairly contained point. The mid-bass hit enjoys a soft forcefulness and decays moderately. Its texture is smooth and the definition is not very accentuated. Globally, the presence of the zone remains one point below the rest of the ranges. As a result, the lower zone is, as a whole, balanced. However, the Rambo have a certain warm face, with a hint of darkness.





Things change here. The ISN have the best mids of all the PK earbuds I have heard. The trend with this capsule is to get a range of 200Hz up to 1kHz quite pronounced and present. The Rambo manages to invert this particularity and its curve descends from 300Hz, allowing to compensate the effect on the mid zone with this capsule, lightening the response in that zone. This is a very clever choice, because some negative peculiarities are avoided, such as the presence of male voices, with their consequent large dose of mud, nasal and even metallic sound. None of this is perceived here. The Rambo have a very balanced vocal range between male and female voices, without one prevailing over the other. In addition, the naturalness improves enormously, offering a very balanced texture, that conjugates warmth and certain darkness, with a light brilliant spark, that contributes clarity, detail, separation, space and air, but without contributing any sibilance.

It is true that the voices are in a closer plane than the rest of the instruments, which makes it very suitable for genres with vocal predominance and few instruments. But the rest of elements also enjoy all the virtues that voices have, but with a point of distance. Thus, they are also a delight for rock or pop.





The upper area has the typical PK flash, but it occurs earlier and is narrower. Thus its incidence is noticed something different but in a beneficial way. The brightness is observed, noticed and perceived in a quite complete way, but wide, extended and not very sharp, free of fatigue. It offers a good dose of air, good level of detail and brings good clarity and separation to the sound.



Soundstage, Separation


The ISN Rambo have a wide enough scene for earbuds. The feeling of three-dimensionality is limited by that certain lack of depth, but still offer a good feeling of recreation spherical and quite zenithal. The positioning is good, but with a closer predominance of voices over the rest of sounds. The level of separation is appreciable, within the parameters of naturalness and equilibrium that characterize these earbuds, without being either excessive or unreal.





DQSM Z & W Panda PK2s


The comparison is necessary, because the Panda are so popular, but they are not at the same level. The Panda have that over-emphasized sound in the lower section of the mids, which characterizes some models with a PK capsule. They sound clearly muddy, congested, muffled, nasal, unnatural. Moreover, in this case, the Panda has a very smooth treble and less extension, which also helps to muddy the sound in that mid zone and to turn off its profile more.

In terms of scene, separation, instrumental recreation, three-dimensionality, etc., the differences are just as great. And it is true that the Panda cost a third of what the Rambo, but in this case the price difference is totally justified.



Ourart Ti7


The Ourart Ti7 are a worthy rival for the Rambo. Although in the lower zone the Ti7 have clearly less global presence, the impact of the bass is faster, drier and more contained. The Rambo offer a more complete zone, with more body, punch and incidence in the rest of the sound. In the Ouart, the global absence of the lower zone frees the sound, but depending on the genres and/or songs, it is somewhat orphaned.

In the mid zone the differences are maintained, the Rambo have a warmer profile, sweet, natural, more compact and homogeneous. Meanwhile, the Ti7s are colder, more analytical and, although the graphics do not reflect this, their sound is brighter, with higher resolution, cleanliness and separation. The presence of the voices is similar in both and both give them special attention and emphasis, but each one focuses them from their profile.

The trebles feel more present in general, in the Ti7, although locally, the Rambo offer a more crunchy hit in the lower area of the trebles.

In terms of separation, the greater openness, clarity, air, definition and resolution of Ti7 is above the Rambo. The scene feels bigger in Ti7 too, while Rambo offers a more intimate and compact ensemble, not so ethereal or open, but also more realistic and natural.

In short, Rambo has a warmer, analogical, compact, balanced and natural profile, as opposed to the cold, analytical, brilliant, ethereal and open profile of Ti7. They are two profiles rather complementary than opposite.





The ISN Rambo is a candy inside a PK capsule. Intelligently tuned to conjugate the sonic characteristics of this envelope, with a driver designed to use, obtaining the best synergy to offer a natural sound, organic, analogical, balanced in bass, with great voices and a wise dose of brightness. A charming man, this Rambo.



Sources Used During the Analysis


  • Burson Audio Playmate
  • Xduoo X3II
  • F.Audio S1