Works great for any iem out there. I previously only religiously bought apple dongles as my got-to portable dac. Only later I found the audiocular spark which had the CX31993+ Max amp and provided slightly more power. It works exactly like it says and gives 1.4 v vs the 1 v of the apple dongle. So if some extra power is what you’re looking for, the audiocular spark is what you need. This is going to power all your iem needs.

I love these iem’s . This is end game iem for me since expensive ones have diminishing returns
I really like audiostore delivery

Spectacular DAC, boosts the audio well. Great music experience.

TL;DR:
Finally jumped into the IEM world with the Bunny and I am blown away. Super clear highs with zero harshness, smooth vocals, and punchy bass. Works great across all genres I listen to, super comfy, and keeps getting better over time. Only downsides: cable’s a bit short but that is subjective and movie audio can be hit or miss. Overall, I’m honestly blown away by how good these sound for the price.

I have been contemplating getting into the IEM world for the past few years and when I finally pulled the trigger on this one, it just blew me away and I am not even exaggerating. Before getting these I was using OneOdio Headphones that I got for 4k that I still love but, well, when I got the Bunny's I was like, is this what have I been missing out on ?!?!
This long contemplation for getting an "IEM" was also because of conflicting reviews about some of them like some having high sibilance or thin sounding bass or something else and I couldn't make up my mind to get one or the other. I'll be honest, I was kind of scared if I might not like these or I might find them too sibilant as I am pretty sensitive to that, and I was already expecting the bass to be less than what I am used to before hitting the play button. All of my worries went away as soon as the music started, the highs and vocals were absolutely clear and bass hitting just right. I did try tip rolling to see which eartip gave the best seal. I don't know if burn-in is real or not, but it has been a month since I got them and they have just kept getting better and better.
I listen to a lot of DnB, Experimental or other EDM subgenres along with Jazz, Orchestral, Movie scores and songs with vocal etc and they work for all the genres in such a nice way! I'm seriously trying out new genres at this point because everything sounds so fun with them. The vocals are so smooth and just the right amount of sparkly and the bass either the sub or mid is not at all lacking by any chance. I won't be able to talk much about the soundstage but if I say so, listening to Yosi Horikawa, Snarky Puppy, Tipper is an absolute fun in these. Everything just sounds like it is there as it should be. Separation is great compared to my headphones. I am indeed hearing things that I haven't before but that might also be because of the bass not muddying everything up.
They are small so they fit me like a glove (subjective but still) and are so comfortable to wear for a long session or even while lying down. I just wish the cable were a little longer but its still fine. The included bag is pretty handy and the included tips have a pretty good selection to get a good fit.
I'm definitely getting a DAC and maybe in the future a Balanced cable just to see how much can these be pushed and what sound these can deliver.
The only few things I'd say is that watching movies or shows could be a hit or a miss with these because of the way they might be mixed/mastered and as these being balanced they don't hold back on any frequency or muddy up the other. The other day I tried to watch Chris Nolan's Tenet with this, but the gunshots were a little too harsh or the voice was too low to hear properly but Ford vs Ferrari, Mission Impossible or Star Wars were very fun to watch. Might be a subjective opinion but I thought I'll add it. The other thing is that I thought these would be good for making music as I do that for hobby but I still have to test them out more in that scenario.

It is very efficient and clean sounding. I loved the amplification which is enough to drive demanding planar magnetic headphones. The functions and display is very intuitive. Overall a very good product.

A goodpurchase awesome improvement in the bass with no extra noise!

It is really good for the price

The IEM's are really good. The build quality is great for the price

I am using this for my daily use. This is so good even tunable to an extent. Good quality build and audio

Best in class adapter for various IEM's. I used it with KZ caster, Fiio JD1 and KZ ZEX. All works perfectly. My choice currently is with KZ ZEX. Instead of Touch, button system to control is too good and easily fits in our ear. ANC is not too aggressive, but quite good. Transparency mode is effective. So finally it's a perfect buy for our IEM's. KZ Rockzzz.

Got this over Waner II and Bunny DSP and it was totally worth it. Loving it so far. It supports my s21 FE and Lenovo LOQ Laptop. Let's see how long it lasts.

It’s neutral and clean and slightly warm because of copper.
This cable is perceived as giving a slightly warm-toned character, with clarity and neutrality in the mix.
Superb quality. Very flexible & easy to move around. Good sound quality, it works well in practical use with their DAC/AMP chain.

It Perfectly fit my bunny's. Fixes to ear way better and Definitely heavier than the default dsp cable.

The FiiO BTR5 2021 is a well-regarded portable Bluetooth DAC/AMP known for its strong decoding ability thanks to the dual ES9219C DAC chips. It supports high-resolution audio, including MQA decoding and up to 16x MQA [Discontinued, but not completely] unfolding when paired with compatible sources. The device provides versatile connectivity options such as balanced 2.5mm and single-ended 3.5mm headphone outputs, USB-C DAC functionality, and Bluetooth 5.0 for wireless listening. It features a sleek design with an aluminum and glass build, accented by a small display that shows audio info, though the display can sometimes be unreliable in showing the exact source or codec.

Compared to the original BTR5 from 2020, the 2021 model adds MQA support, a new DAC chip for better performance and noise ratio, and an improved USB audio adapter mode that disables charging during USB DAC use. It comes with a short skin-friendly USB-C cable and a redesigned packaging.

One critical caution for the BTR5 2021 (MQA version) is with the FiiO Control app's equalizer function: using the EQ on the device firmware via this app can brick the device permanently. Users recommend applying EQ only on the phone side with apps like Wavelet instead, to avoid this issue.

In its price range, the BTR5 2021 remains competitive, especially for users prioritizing sound quality, build, and MQA support. However, some users compare it with newer or alternative models such as the FiiO BTR15 (which offers Bluetooth 5.1 and 4.4mm balanced output) or the Qudelix 5K(Gone forever), which has more extensive software EQ features but a less premium build.

Overall, the Fiio BTR5 2021 is a solid choice for audiophiles wanting a portable DAC/AMP with both wireless and wired support, especially if you avoid the Fiio app's device EQ to prevent bricking issues. It has a mature firmware, strong sound performance, and versatile connectivity suitable for IEMs and headphones.

After a lot of deliberation I bought this as my first IEM. Loved it at my first listen. Still my go to IEM. It has a slight u shape that gives a musical tone to the sound. Caters to a lot of genres. It can be driven by 60mW cheap dongle DAC and amps. Absolute value for money.