Review - Kiwi Ears Allegro

Review - Openheart Resin (Sub 50€)

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Also available on YouTube in Spanish: Acho Reviews YouTube 


The Openheart Resin are a set of IEMs that I have seen mentioned a few times amongst the lovers of budget IEMs and the mention of these were what led me to purchase the Grado-style OH2000 that I reviewed recently.

In the case of these IEMs, I also don’t know much about them at all, all I know is that they don’t have a model name other than “Resin”, at least to my knowledge.

At a price of around 20€, this is another entry into the budget category, far below my sub-50€ barrier, where there is more and more competition lately.


I purchased the Openheart Resin without a cable, appreciating the fact that it is an option and doesn’t involve me having another cable I won’t use (although the Openheart cable that came with the OH2000 was actually quite nice).

They arrived in a small brown cardboard box with Openheart written on the top. Inside, the IEMs were in a small antistatic ziplock bag with another smaller bag containing a selection of silicone and foam tips in various sizes.

The only other thing included is a small microfiber cloth with the Openheart logo, this is something that was also included in the OH2000 so it must be a standard for them, even if it is not a common thing to receive with headphones/IEMs.

Build and aesthetics…

The IEMs are solid resin shells (as the name may suggest) and in my case they have a light blue tint to the clear resin.

The shape is very reminiscent of the Tianderenhe TD02 that I reviewed recently and I find them very comfortable when in place. They do seem to be slightly lighter than the TD02 although there certainly isn’t much in it.

The IEMs use a 10mm Dynamic Driver enclosed inside the cavity which has a small vent tube running from it to the outside of the shell.

I don’t mind the looks of the Resin at all, although I don’t think they look as nice as the TD02. It is also probably worth noting that there are absolutely no markings on the IEMs (brand or model).


My first impressions with the Resins using the included silicone tips was that they were slightly sibilant and had a bit too much bass and were not quite controlled enough in the lower regions. I played around with various tips and the included medium sized foam tips just clicked for me, giving me great comfort and the sound that I am about to share.

Starting, as usual, with the sub-bass frequencies, there is plenty of extension down into the lowest regions, giving plenty of rumble on those tracks that need it. The subbass was a little more present with the silicone tips but the foam tips cleaned it up a lot and made the lowest hits sound cleaner and more defined. Listening to some D&B and some electronic music with extreme bass drops, the Resins provide plenty of that low end.

Moving into the higher ends of the bass, they remain controlled and very clear, with a slight emphasis on bass which should be enough for the bass lovers. Whilst they do have an elevated bass range, this is not too exaggerated in my opinion. In songs that use real instruments rather than electronic samples, the bass sounds very realistic and natural, except for that slight boost which I don’t find annoying, just not my preferred tuning as you all probably know by now.

In the lower mids, there is a slight overhang of the bass into the lowest mid frequencies but it is not enough to be unpleasant, just a touch too much for the most realistic timbre of the lowest acoustic guitar notes.

There is a dip in the center of the mids, as with all V shaped IEMs, which can make voices sound a little recessed in their roots depending on the amount of bass in a track. For example, “Way Down Deep” by Jennifer Warnes does exhibit that little extra bass that can sometime overshadow her voice in the lowest registries but in general the sound is rather pleasant on most songs and vocals are not too bad if you are someone who likes this kind of signature.

The higher end of the mids rises to a peak somewhere between the 2 and 3kHz mark, bringing back the presence of vocals. Although the avoid most of the harshness or nasal tones in vocals, this can prove to be a little shouty with brass instruments such as in “Diamonds on the Soles of her Shoes” by Paul Simon.

Up into the higher registries, sibilance is reduced a lot by the foam tips in comparison to the included silicone tips, it is not totally absent but it is reduced to a level that allows tracks like “Code Cool” to be listenable, although you can still notice it. Strangely, I heard more sibilance on Paul Simons vocals with these than I have on other IEMs, whereas my usual test tracks weren’t bad. There must just be a certain frequency in Simons voice that resonates.

The high end obviously suffers from the usual single DD roll off, however, it doesn’t leave the sound dull or seemingly lacking in treble. That slight touch of sibilance sort of adds an impression of air that is not really there. To be honest, I don’t really have any complaints about roll off, sure they could extend more, but they are better than many others I have tested.

The speed and dynamics of the Resin’s is pretty good, not seeming to become overly pressured when listening to fast tracks and the details are also quite impressive for a set of IEMs in this price range. They are not amazing but they do portray a sense of detail, especially in fast tracks, that is superior to many others in the sub-50€ price bracket.

As far as stage width, they are in the average bracket, maybe slightly better than average in this price range. However, image placement inside the width is rather good and makes it easy to locate and place different instruments and effects, even if they are not that wide.


At 20€, the Openheart Resin are a set of IEMs that offer far more than their price range would suggest. In comparison to other similarly priced IEMs I have reviewed lately, these are certainly one of the better options.

The tuning is not quite my preference but it is not irritating and the cleanliness and control of the low end (with foam tips) makes it much more to my liking.

We have seen a lot of options around this price bracket lately, some of them being very good and these are one of those sets that firmly contends for the sub-50€ bracket. I still feel that the Tin T2+, the KZ ZAX and the KZ DQ6 are above these in my preferences but the gap is starting to get smaller and smaller.

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