Heartfield Acoustic Deer Review: Much bling bling

I tend to test bigger brand IEMs in general but once in a blue moon I’ll get the chance to try something from a new company and I was recently sent the Heartfield Acoustic Deer IEM to check out and review. This is a smaller 6.8mm single dynamic driver unit coming from Heartfield. The Acoustic Deer comes in at $169.00. I will be referring to the Acoustic Deer simply as the Deer for the rest of my review to make my life easier.

Quick shoutout to Linsoul for sending the Acoustic Deer to review. While I always appreciate the chance to test and review products sent in from manufacturers, it never affects the rating of my reviews.

The Acoustic can be picked up from Linsoul at their website below.


Gear Used

IPhone 12 pro with headphone adapter, Lotoo Paw S1, Khadas Tea, SMSL SU-9 feeding the SP400 amp.

Looks and fit

I’ll start out by saying I personally hate the looks of the faceplate being used on the Deer. The shell is a nice polished metal which gives a mirror finish. The faceplate uses a “gem like crystals” that make the IEM look like something that would come out of those bling bling item stores you see at the mall. It just simply doesn’t do it for me. What does “do it” for me is the fit and comfort. The shells are like the perfect size for my ears and it makes a super secure and comfy seal and I can listen to these for long sessions without any issues at all.

Isolation and sound leakage

The passive Isolation is good here. This isn’t a normal single DD IEM that uses vent holes to relieve pressure from the driver. The issue with vented IEMs is the sound leakage that tends to be louder and not that good for quiet areas. Since the Deer is sealed, I don’t hear much of the outside world and the sound leakage is very minimal. I would absolutely be ok using this in a quiet office or on a plane.

Packaging and accessories

The Deer comes in a green/teal box that is fairly simple. It flips open to reveal the IEMs, under that is some eartips and the warranty card. Super straightforward and while I’m pampered by companies like DUNU and Moondrop when it comes to awesome unboxing experiences, I’m alright with a basic setup for IEMs like this.


These final impressions were done off a mix of the Khadas Tea, Lotoo PAW S1 and the SMSL SU-9 connected to the SMSL SP400. These are what the Acoustic Deer sounded like to my ears. This was also using CP360 eartips from Spinfit. Things like ear tip selection and DAC/amp selection will produce different results and impressions vs what my ears hear on my specific gear.

The Deer goes for a warmer single DD sound signature. It has decent subass performance with a noticeable thump when called for. It has a more intense midbass however and I think this is due to the non ventilated design. It can sound a little congested at times and it causes some bleed into the lower mids. That being said, It has a fuller sound and for the most part I’m alright with the way the Deer handles the bass. This could also be due to the smaller single DD driver being used as well. The mids are above average in my books in terms of guitars and vocals quality. The instruments have a warmer tone but vocals go for a smoother presentation. Male vocals sound super smooth and enjoyable but I find the female vocals to be a little muted in comparison. The upper mids to lower treble do have a boost that comes in a little strong for my tastes. It’s not quite sibilant but it’s definitely noticeable. The rest of the upper frequencies are somewhat relaxed. This is always the trade off with single DD IEMs for me. Something has to give and for the Deer, they go for the warm signature that has lacking details in the highs. The boosted upper mids help keep things sounding good but I do feel a lack in overall treble detail. There is just not as much energy or air up top. I still like the tuning of the Deer. I personally like to see a single DD lean more towards a brighter sound.


The soundstage on the Deer feels about average. I think depth and width aren’t anything special. I however found imaging was fairly decent given the average stage. I just don’t have much to say when the staging sounds like a lot of other standard fully sealed IEMs in this price range.


The Deer is rather easy to run and I was able to run it fine off everything. It isn’t overly sensitive which meant I had zero floor noise issues on all the source gear I tried with the Deer.

Stock cable

The stock cable being used is a nice twisted braid in a dark grey/silver finish. I found the cable to hold its shape well. It’s a super simple cable in 3.5mm and I have no issues with it. I would leave the stock cable installed unless you wanted something to use with balanced source gear.

Tip rolling

I didn’t go super crazy with tip rolling. I did find the Spinfit CP500 and CP360 to be my favorite set of tips to use on the Deer. Wider tips give the deer a little extra treble and the CP360 gave the warmer sound that I talked about in my sound impressions section. I didn’t find the deer to make a big difference on tip rolling but I always recommend playing around with tip rolling with almost every IEM.

IEM comparisons

DUNU Falcon Pro

The Falcon Pro comes in closer to the Deer price wise but does cost about $50 more. I would honestly say both sound about the same tuning wise. I do find that the Falcon Pro comes in just a little cleaner overall. The Falcon Pro is heavy ventilated however and leaks sound like crazy. This does however allow the Falcon pro to have a less hazy mid bass that I hear in the Deer. Outside of that, both sound very close in tuning. I will say the Falcon pro handles its stage a little better by being wider sounding than the Deer. I will admit I really like the whole package of accessories that comes with all DUNU gear and that maybe the extra cost is worth it(at least to me). I would also say I find the Deer to be more comfortable for my ears and maybe some money could be saved by sticking with the Deer.

Moondrop Aria

The Aria goes in the opposite tuning of the Deer with a brighter sound overall. I think the Aria is crazy well tuned and I would say this is my preferred single DD tuning. The Aria lacks some of the bass impact that the Deer has but it has clear mids that have better vocal performance. The treble does sound better on the Aria but both lack top end detail and I would say the Aria falls behind is some overall detail retrieval but it's close between the two. I do find the Deer is way more comfortable over the Aria for my ears. I would say go with the Aria if a brighter signature is wanted and to grab the Deer for a more relaxed sound that can be had for long sessions.

Amping Combinations

Lotoo PAW S1

The S1 pairs well with the Deer. I would say the warmer sound signature of the S1 doesn’t quite help the Deer’s already relaxed sound but this can be solved with the S1’s included sound presets. The S1 does bring out a wider stage in the Deer and with the brighter preset(dental) I preferred this pairing. Those who don’t like EQ or built in presets will wanna grab a brighter source.

Khadas Tea

The Tea is also a warmer sounding DAC/amp but I constantly use the Tea everyday since it’s so easy to pair to my iPhone via Bluetooth. I used this combo a lot while testing the Deer. I like the combo but the warmer sound didn’t really bother me much. I think the Deer can sound a little hazy and veiled on the Tea but like I said in S1 section above, Go for that or a brighter source, such as the Moondrop Moon River 2.

Overall thoughts

I ended up liking the Acoustic Deer’s warmer tuning but I do wish they would have gone with a vented shell in order to help the lower mid congestion. I found the Acoustic Deer to be super comfy and it was a nice IEM to listen to while relaxing. I will be giving the Acoustic Deer a recommendation. That being said, It makes for a good secondary or “compliment” IEM to something else that you might be using as an all rounder. I wouldn’t call the deer a full “all rounder” unless you really like a warm overall tuning. I wasn’t into the bling bling look of the faceplate but that is a personal preference thing. I look forward to seeing what other new offerings start ups like Heartfield have to offer in the future. Thanks for reading!

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