Review: FiiO FD1 – The New Series

FiiO FD1
FiiO FD1

After achieving maturity in the FH (hybrid) series and FA (BA) series, FiiO decided to release another series – FD (dynamic) series IEMs to address the needs of different groups of audiophiles.

Thank you, Nappoler Hu from HiFiGo for sending me the FD1 IEMs. It was provided to me free of charge in exchange for my honest review and opinion.


Established in 2007, FiiO, an audio gear manufacturer from China has rich experience in researching and developing various types of portable music products, such as IEMs, amplifiers, and DAPs. The brand name FiiO is composed of “Fi”, which stands for fidelity and “iO” which stands for number 1 and 0 in digital language.

I first came across FiiO products in 2015. Back then, FiiO was one of the best choices for budget DAPs and amplifiers. FiiO slowly extended its expertise to other regions of the audio industry.

In the same year that I started to be more familiar with FiiO, they released their first IEM – EX1. This is where my FiiO journey started. From EX1 to today’s FD1 – this article’s feature – FiiO refreshed their lineup numerous times and the improvement is huge.

Let’s take a look on the new FD1 and check how far FiiO has progressed since their first release!

FiiO FD1
Bottom Line

As the first model in this series, I believe FiiO is targeting bass-head audiophiles. Warmth and bass lovers will definitely love the FD1. However, for those who need a high level of detail retrieval capability, like me, the FD1 should be avoided. It can be a pair of good IEMs for casual listening, but definitely not for monitoring.

What We Like
  • Lightweight
  • Premium stock cable
  • High quality storage case
  • Good warmth in presentation
  • Non-fatiguing
  • Affordable pricing
What We Don't Like
  • Overly emphasised bass
  • Narrow soundstage
  • Shy treble
  • Lack of details
  • Below average fitting and isolation


I would consider FiiO FD1’s packaging a luxury for a pair of IEMs that retails at less than USD$100. FiiO is doing standardization, just like many other major brands such as Sennheiser. The packaging of FD1 is similar to FH1s, which was launched earlier this year. Even from afar, consumers can now recognize FiiO products.

FiiO FD1's packaging
FiiO FD1’s packaging

I hope FiiO will continue this. In the past, their branding always seemed to vary, making the whole series appear messy and directionless.

The packaging provides minimal information. Opening the box, there is a user manual. After that, the FiiO FD1 presents itself to users, well secured by foam. The cable and pair of ear tips are pre-installed. At the bottom part, there is an accessories box to keep all the remaining contents safe.

Here are the accessories in the box:

  • A pair of foam ear tips
  • Three pairs of wide bore opening silicone ear tips
  • Three pairs of narrow bore opening silicone ear tips (a pair is pre-installed)
  • HB1 storage case
Accessories in the box
Accessories in the box

Technical Specifications

  • Driver: 10mm beryllium plated dynamic driver unit
  • Impedance: 32 Ω
  • Sensitivity: 109 dB/mW
  • Frequency Range: 10 – 40,000 Hz
  • Cable/Connector: 0.78 mm 2-pin

Build and Design

FD1’s shell is made up of two pieces of acrylic – the front cavity and it’s faceplate cover. This design is also found in the recent release, FH1. This design helps to reduce the weight, as well as the cost imposed to the customers. Unlike FA1 which is built using 3D printing with resin material, FD1’s acrylic shell is definitely lower in cost and easier to produce in bulk.

FiiO FD1's faceplate
FiiO FD1’s faceplate

The faceplate is made of celluloid. There is a golden FiiO logo printed on the faceplate. Unlike other IEMs where the faceplate is exposed, FD1’s faceplate is covered in the shell by a piece of acrylic.

Celluloids are synthetic plastic, which is produced by mixing nitrocellulose and camphor, often with added dyes and other agents

FD1 is utilizing a 0.78mm 2-pin connector, which is commonly found in the majority of the IEMs. The 2-pin connectors slightly protrude from the shells and they are protected with a layer of plastic. This can increase the durability of the 2-pin connectors. The protrusion is not as much as TRN VX or Simgot EK3. I can still use normal 2-pin cables on FD1 without any issues.

The 0.78mm 2-pin connector
The 0.78mm 2-pin connector

Moving on to the aluminum alloy nozzle, there is a lip to provide a good catch for the ear tips. The nozzle diameter is around 5mm. A lot of third party ear tips, such as Final Audio Type E can fit to FD1 well.

The nozzle of FD1
The nozzle of FD1

The stock cable provided by FiiO for FD1 surprised me. In previous releases, FiiO always threw their cheapest cable into the packaging. I expected the same low-quality cable for the FD1, too. But not so. FiiO gives us a four Litz wire braided monocrystalline copper cable. For those who are unfamiliar, Litz braided monocrystalline copper cable is a great upgrade compared to conventional silver plated copper cable or oxygen-free copper cable.

The stock cable
The stock cable
The cable is neatly braided
The cable is neatly braided

Here is a suggestion for FiiO, since the cable has been upgraded: I think it would be good to have a termination option for consumers. The cable by default is 3.5mm unbalanced terminated. As a balanced output user, I will need to replace this cable with a balanced cable in order to utilize my balanced output. It will be more feasible if FiiO can provide a balanced option.

Fit and Isolation

With its material choice, FD1 is light and it does not exert any pressure on the ears during use and is suitable for long listening. However, I find the shell is less than completely ergonomically designed. Based on my experience, FiiO FA series always has the best fit because of its 3D printed semi custom shell. FH and FD series always give me fitting issues.

With the provided silicone ear tips, I can hardly find a comfortable insertion into my ears. It simply does not seal. I have tested it with multiple ear tips from different manufacturers such as SpinFit and Final Audio; all of them are providing below average seal. This could be a deal breaker.

I believe the isolation can definitely be improved if they were to use FA series 3D printing technology here – but the cost will definitely be higher.

FiiO FD1
FiiO FD1

Sound Analysis

Rated at 32 ohms for impedance and 109 dB/mW for sensitivity, FD1 could be considered a power efficient IEMs. I can easily drive it with my DAPs, as well as my iPhone XR. However, due to the driver configuration, a more powerful source will definitely be in favor of better sound quality. This is always the nature of a dynamic driver.

FiiO FD1 with Lotoo Paw 5000 mk II
FiiO FD1 with Lotoo Paw 5000 mk II

The FD1 has a thick and lush sound profile, with a little warmth from the lower end. I would not call it neutral or transparent. It has a certain degree of coloration and smoothening, yielding an enjoyable and non-fatiguing presentation. As a pair of dynamic driver powered IEMs, FD1 has relatively good speed compared to other IEMs with the same configuration, such as KBEar Diamond.

The soundstage of the FD1 is average. It has good depth and layering on the Y-axis. In terms of width on the X-axis and distance on the Z-axis, FD1 has huge room for improvement. Due to the smoothing effect, the notes are stretched, to be thicker. This caused the room and space to be fully occupied. When the track is more complicated, congestion happens.

FiiO FD1 on Astell & Kern SR15
FiiO FD1 on Astell & Kern SR15


Just like other dynamic driver powered IEMs, FD1 has a good rumble in bass. However, when we take a closer look into the sub-bass and mid-bass, we realize that the FD1 actually has a small degree of sub-bass roll off. The rumbles are actually from the mid-bass. Here’s the problem; when mid-bass is overly emphasised to create the rumbles, mids will definitely be affected. This is where the coloration comes from.

The thick and full bodied mid-bass of FD1 is boosted, to create the rumbles which the sub-bass is lacking. It did its job well.

The sub-bass and mid-bass address each other’s weaknesses, creating a good quality bass, with sufficient quantity too. It has an average speed of attack and decay, to yield a good dynamic in the presentation. It injects good warmth to the overall sound signature, too, making it enjoyable to listen to. For bass-head audiophiles, FD1 can definitely fulfill your needs.

FiiO FD1
FiiO FD1


As mentioned in the lows section, the mid-bass rumbles caused the warmth from lows to be carried forward to mids and caused them to be colored. I would not call the mids transparent. The warmth is injected in a positive way – giving soul and emotion to vocals. The vocals are smoothened, with a lush body and good penetration.

In some of the pop tracks, when there are more mid-bass instruments, the lower mids, especially male vocals, are covered with some muddiness. The spotlights are snatched by instruments like drums. For those who appreciated bass more might not find this as a weakness but to me, I think the balance between mids and lows is off. They should co-exist, instead of fighting each other for the spotlight.

Upper mids are further from the mid-bass; it’s not as heavily affected as the lower mids. Female vocals and higher frequency instruments can co-exist with the mid-bass rumbles. The upper mids have warmth too, but with smaller magnitude. The presentation is more transparent here. The space is sufficient for the notes to flex. However, more space and air are definitely welcome – another room for improvement.

FiiO FD1
FiiO FD1


The highs of the FD1 is the most polite region. You might not feel it if you’re not paying attention. The bass region gives too much emphasis, causing the highs to be shy. This can be good for those who like less-fatiguing IEMs. It’s not bright, at all.

However, due to the lack of presence in the highs, it affects the space, air, and fidelity of the presentation. This is why the stage is congested.

With help of a better extending, more airy and spacious highs, the FD1 might have a better fidelity.

A lot of micro-details, which need higher level of detail retrieval capability in IEMs, are missed by the FD1. They are shadowed by the thick and full-bodied macro details. This scenario is most obvious in the highs. On those tracks with more bass and mids emphasis, the high-frequency instruments are unable to present themselves on the same level with other instruments. They are suffering from the coloration and smoothening.

FiiO FD1
FiiO FD1


As the first model in this series, I believe FiiO is targeting bass-head audiophiles. Warmth and bass lovers will definitely love the FD1.

However, for those who need a high level of detail retrieval capability, like me, the FD1 should be avoided. It can be a pair of good IEMs for casual listening, but definitely not for monitoring. FH1s or FA1, entry-level models from the other two series, might be a better choice for you.

FiiO FD1 is retailing at USD$69.99. You can purchase it from HiFiGo.

After listening to FD1, FH1s and FA1, the three entry level models from FiiO, I believe each of them is designed to cater to different groups of audiophiles. FD1 is definitely for bassheads. For bass lovers with strict budgets, go ahead with FD1. It’s bass will not disappoint you!

FiiO FD1
FiiO FD1

1 comment

  1. Im going to chalk this up to FiiO’s sus quality control because I feel like we are listening to two completely different iems. I found the FD1 to be just above bass neutral, with decent overall resolution but an extreme gain in the pinna upper midrange/lower treble region that made them sound too strident. Not sibilant, but they tried to manufacture treble resolution and air and it comes off making them sound like your ears arepressurizing on an airplane. The upper-mids are thin because of this, lack any romance and the overall sound to me is lifeless. I tried every tip combo, and Final E-tips. Nothing cut that pinna gain enough. had 3 different sources too.

    These are not basshead iems either. The BLONBL01 have significantly more bass and bleed than these. As do the Final E2000. Has to be FiiO with their random Quality Control.

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