Sendiy M1221 hybrid IEM – Balance in a stunning shell

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Yet another earphone manufacturer hailing from China, Sendiy came onto the scene in 2016 with their M2, a wooden IEM that came out of the gate with a lot of praise and recommendations. Things went awry shortly after when another seller released their own version which looked identical but was reported to be inferior sonically.

Controversy aside, the people who got the genuine article seemed to be very pleased with it. Fast forward to late 2016 and Sendiy released a new flagship IEM, the M1221. It’s a hybrid unit with a single Dynamic driver plus one balanced armature. Is it any good? Let’s get on with the review then and hopefully by the end you’ll be able to decide if this is one you’ll want to add to your collection.

The Sendiy M1221 is currently priced at $199 and is available from Sendiy’s Aliexpress store:

This product was provided for the purpose of an honest review. I’m not affiliated with the company and all observations and opinions here are my own.

  • All-metal shells
  • Very nice storage case and lots of accessories
  • Customizable sound with tuning nozzles
  • Lacking dynamic range


Drvier 1x Dynamic + 1 BA
Impedance 20 Ω
Cable 1.2 m, 6 core silver plated copper
Sensitivity 110±5dB

Packaging and accessories

The M1221 comes in a very nice, irregular hexagon-shaped black box, complete with little pyramid-shaped metal studs securing the carry strap and box clip. On the front is the Sendiy branding in glossy silver and the company’s motto “Music changes life–enjoy it”. On the back is a list of features and specifications along with a frequency response graph and a diagram of Sendiy’s unique driver configuration (more on that later).

Inside the box is the provided carrying case which holds the earphones and all of the accessories. The case is a bit unusual compared to what we usually get with IEMs in that it’s an IP68 graded water and dust proof affair (similar to Pelican cases) that has a waterproof depth of 33 meters and can withstand falls from heights up to 5 meters. It’s a very nice case indeed, although it does require a bit of force to open and close. Sendiy was also considerate enough to provide an additional regular semi-hard case that’s pocket and bag friendly.

Alright, let’s take a look at the full list of accessories that come with the M1221:

  • M1221 earphone
  • x2 detachable silver coated cables with MMCX connectors
  • 6 pairs of tuning filters (silver, gray and black in 6mm and 8mm variations)
  • 2 pairs of foam tips
  • 3 pairs (S, M, L) double flange silicone tips
  • 3 pairs (S, M, L) single flange silicone tips
  • carrying case
  • shirt clip

As you can see there’s fairly comprehensive list of accessories provided and should include everything you could want to get sorted. The only thing I would wish to see added is some larger ear-tips as every one of the 8 pairs were too small for my ears but to be fair that is the case with 4 out of every 5 earphones I get. Luckily I have a personal collection of extra large tips on standby so I was ready to go in no time.

Both of the provided cables are very nice but the upgraded braided one is my preference. It’s braided with metal, colour coded MMCX connectors and a heat shrunk plastic tubing that forms nicely over your ear. Microphonics are practically non-existent and it feels supple yet sturdy. There are a metal chin slider and Y-split with good strain relief. The cable terminates in a 90° 3.5 mm plug that is a nice mix of metal and translucent plastic.


Sendiy M1221 accessories

Build & Design

These things are light, much lighter than you’d expect for a metal earphone but Sendiy has used an aerospace grade aluminium alloy that supposedly has 10 times the hardness and density of normal metal. Well, I’m no metallurgist so I’m going to take their word for it.  I can tell you however that the housings feel incredibly strong and the build quality is just superb.

The CNC carved housings feel great in your hand and everything is aligned perfectly. You can barely feel the seam where the two halves are connected. All the surface is smooth and rounded with not a sharp or straight edge to be seen, or more importantly felt when in your ears.

On the outer sides of the housings is the Sendiy branding in a concave recess that runs from front to back. There aren’t really any other features worth mentioning except for the minuscule port that’s just under the front end of the MMCX connector. My description probably hasn’t done the build justice. I believe you’d have to feel them in your hand and take a real close look to get a grasp of how well these are constructed as pictures just don’t do them justice.

The tuning filters are also expertly crafted with a series of notched rings on the surface, similar to a crown on a wristwatch. These make the filters very easy to grip and turn when inserting or removing them and they also have the added benefit of letting you choose whether to have the ear-tips slightly extended from or flush with the end of the nozzle as they sort of “click” into place for each position. The threading is smooth and precise and it’s super easy to change filters.

Comfort & Isolation

For this writer’s ears, the M1221 are extremely comfortable because of their light weight, smooth, rounded edges and diminutive size. The two different filter lengths are a nice touch and for me I found the longer ones to give the best fit. I could easily wear these all day long without a problem.

Isolation is about average for this type of IEM, meaning pretty good so long as you’re getting a proper seal and they’re great for blocking out external noise.


Sources used for testing
  • Benjie X1
  • Acoustic Research M20
  • Samsung Galaxy Note 5
  • PC/MusicBee > Sabaj D3 DAC

Tuning filters

There are three filters which are described as thus:

Silver (bass boost)

Gray (reference)

Black (high boost)

The filters have a fairly subtle effect, mainly making slight adjustments to the amount of bass. They work as expected from the descriptions, with the grey filters giving the most balanced presentation. I’ve been listening to a lot of EDM and ambient music lately so have mostly stuck with the silver filters for a little extra body and that’s what I’ll be basing evaluation on.


Bass is very controlled with good impact and excellent separation from the midrange. Even with the silver filters, it remains reasonably tame but there’s enough impact for EDM, hip-hop and other bass-driven tracks. It won’t be enough to satisfy the extreme bassheads out there but for most, it should be more than ample. It’s pretty fast regardless of filter choice and has that solid presence that dynamic drivers bring. Sub-bass can be a lot of fun with the M1221. The undulating sub-bass swoops in Connect Ohm’s “Snow Park” (again with silver filters) and the thick, heavy kick drums is a pretty intoxicating experience bringing some skull penetrating vibrations without any signs of distortion. Overall the bass aspect of this IEM is, in my opinion, one of the highlights.


Mids are delightfully clear and resolving and remain free of the influence of the bass notes. There’s plenty of detail to be found here as well with good separation and space between elements. Female vocals are nice and smooth without sounding recessed or thin and the upper midrange is graciously forgiving. Even Utada Hikaru’s “Traveling” can be listened to at moderate to loud volume without discomfort with its inherent sibilance and bright notes. It’s also a good song to test the mids as it’s a very busy song with a lot going on and can become congested and lose details on lesser IEMs but that’s not an issue here. Male vocals are slightly thinner but sound natural and are not overshadowed by upper midrange instruments.


The treble is well extended but never strident, though it isn’t the most exciting aspect of the sound. There’s not a great sense of airiness but there’s definitely enough presence to lift the sound and keep its balance with the mids and bass. It’s one of those trebles that doesn’t become fatiguing at higher volumes so if the mood takes you there’s no harm in turning things up. There’s slightly more treble than the TFZ Balance 2M but less than the LZ A4 (depending on filters). For the most part, I like the treble here but at times it can be a little stale.


The M1221’s soundstage is neither overly large or small but gives more of a sense of width than any depth. Compared to the LZ A4 it is a bit confined and while it’s far from disappointing it’s fairly ordinary. At other times though, like in “When I Fear You, All Else is Where it Should be” by iiah it opens up considerably and renders the haunting track wonderfully.



While the M1221 does have various filters it can’t come close to the customization possible with the A4’s double filter system. Despite the more balanced presentation of the Sendiy, I find the A4 to reproduce more micro details, even though it has a more coloured sound.

With the silver filters the M1221 has more bass presence than the A4 with black rear filters and overall the Sendiy is a little more forward in the midrange. The comfort of the Sendiy is superior to the LZ because the housings are much smaller, though the A4 gives you the option of wearing over ear or with the cable down.

TFZ Balance 2M

TFZ’s B2M has an L-shaped signature with a weighty low end and has more bass than the M1221 even when using the silver filters. The Sendiy is a little more revealing which is usually expected with hybrids but still comes across as smooth, however, the B2M has a rich organic feel with a silky, intoxicating midrange.

Those who prefer a more balanced approach will appreciate the M1221 but for bass lovers, the B2M is the way to go. Both have great build quality and accessories but the M1221 pulls slightly ahead in terms of comfort due to its much lighter weight and smaller shells.

From left to right: Sendiy Audio M1221, LZ A4, TFZ Balance 2M

Sendiy M1221 Conclusion

Meticulously crafted the Sendiy M1221 brings a well balanced, clear and engaging sound. The accessories bundle should please most people and the IP68 graded storage case is a nice addition, particularly if you’re planning to go anywhere near water with your IEM.

There are some excellent contenders available in this bracket, including the A4 and Balance 2M (in the comparisons above) but the M1221 can definitely hold it’s own with those and would be a solid choice if you’re looking for something more balanced and fairly linear. I think Sendiy has done a great job with this earphone and they are on track to be a very strong player going into the future. If you’re looking for something in this price range the Sendiy M1221 should not be overlooked.

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