The IE 100 PRO is the most recent entry in Sennheiser’s IE Pro series of IEMs, and now that it’s succeeded the IE 40 Pro, it’s also the most affordable.
In this review, I’ll be going over my experience with the IE 100 Pro wireless bundle, which retails for $179.99. This bundle consists of–of course–the new IE 100 Pro IEM and the new Sennheiser IE Pro Bluetooth connector, but each of these components can be purchased separately at the price of $119.
Editor's note - it appears that official pricing is currently unclear. Official pricing is stated as $179.99, however on Sennheiser's own website it's listed at $149.99.
Sources and Music Used in Listening Tests
All the wired listening for this review was done on the Astell & Kern SR25, and the wireless bluetooth listening was done from Tidal on my iPhone 11 Pro. For the listening tests I used music from a wide variety of genres including Rock, Jazz, Classical, Acoustic, Hip-Hop, and latin. I played tracks from my own FLAC library as well as from Tidal Streaming Service (Master Quality).
Packaging and Accessories
At $179.99, the IE 100 Pro wireless is accompanied by a nice suite of accessories. For starters, there is the IE Pro BT Connector wireless adapter, which I’ll briefly cover in more detail. Also included with the IE 100 Pro are four sets of ear tips (S/M/L rubber tips, and one set of M foam tips), a leatherette carrying pouch, a roughly 1.2m, 3.5mm cable with ear hooks for wired listening, and a Sennheiser cleaning tool.
All of the IE 100 Pro’s wireless features come from the IE Pro BT Connector, which is a new accessory from Sennheiser designed to make any IEM from their IE Pro series wireless over bluetooth.
It’s a very simple unit that replaces the standard IE Pro cables, and is worn around the user’s neck. It features AAC, aptX, and Bluetooth 5.0 support, and USB-C rechargeable battery.
Since they hang around the back of the neck, they’re not the easiest to use, but the module on the right side of the IE Pro BT Connector does feature a microphone as well as controls for mobile devices. The buttons on this module have the standard set of commands, such as play/pause, volume up/down, next/previous track, voice assistant, call accept/end, as well as mic mute/unmute.
Overall I think that the IE Pro BT connector works well, with seemingly no loss to sound quality or additional latency. Additionally, its lightweight design is very nice since, unlike similar devices, it doesn’t feel as though it’s trying to rip IEMs from my ears. I will comment, though, that at 10 hours the battery life is fairly short. It’ll easily last through a day of commuting, but for travelling it may not even make it through a whole flight. Also, the max volume you get from the IEMs when using the IE Pro BT Connector isn’t that high, so if you like to do some loud listening, you may be left wanting.
Build and Comfort
The IE 100 Pro’s build is identical to that of its predecessor, the IE 40 Pro. The IE 100 Pro featured in this review has a matte-black finish, but there are also clear and red color options available. For its material work, the IE 100 Pro is rocking a pretty simple plastic chassis that feels fairly sturdy with no creaking or flexing; it doesn’t feel as rugged as the IE300, or as premium as Moondrop’s offerings, but I don’t think any durability concerns will rise even after extensive usage.
For comfort, the IE 100 Pro is a very easy wear. It’s not as small as the IE300, but it’s still on the smaller side for IEMs, so these should fit well even for users with smaller ears. The included silicone ear tips, I found, were very comfortable and I had no issues getting a good seal with them. The included foam tips were also very nice, as they helped in giving the IE 100 Pro a more custom feeling with increased noise isolation; though I do wish that small and large variants had been included.
The IE 100 Pro is using a single dynamic-driver setup, and I’d say has just a very mild V-shape to it. Despite the slightly more energetic bass and treble regions, I’d still say that it leans more towards being a “neutral-sounding” headphone. It has one of the better overall tonal balances I’ve heard in an IEM, and right off the bat I’ll say that this is the best wireless in-ear headphone I’ve heard in the sub $200 bracket thus far.
The bass on the IE 100 Pro is warm, with a focus on the low to midbass frequencies. Whilst the region under 50hz unfortunately doesn’t have as much depth and sub bass presence as I would like to have heard, the bass response on the IE 100 Pro remains prominent by virtue of the emphasized 60hz-140hz frequencies.
For my taste and preferences, I feel as though the bump in the midbass frequencies can make for an ever so slightly bloated bass response that I think could have used just a bit more precision and contouring. Still, I will note that the accented midbass does make for a more “fun” bass response and it seems to help the IE 100 Pro in creating a heightened sense of slam that lends low tones extra kick.
The mids on the IE 100 Pro have a great tuning, and because of the more “neutral” balance, they sound quite a bit richer and more prominent than on the IE300. The fundamental range here between 300hz-600hz is well-defined, and it gives vocals and instruments alike a robust body. Additionally, the upper midrange between 1K-5K has proper presence, with a good representation of overtones that lie in that region without coming through as forward or shouty.
I really enjoy the treble region on the IE 100 Pro. It has a very gentle rise between 6K-12K that can put a small stress on consonant sounds, and its highs are just a little on the brighter side. However, I think they have the right amount of brilliance where despite feeling more energetic, they’re not harsh or piercing.
I think that this tuning for treble region plays well with the also slightly boosted lower to mid bass response, and I think that it helps in creating an enhanced sense of clarity in the upper registers. I think it’s also worth mentioning that I found the IE 100 Pro to have good upper treble extension, as the air frequencies above 10K had good presence, and added a very nice glisten up-top.
Admittedly, going from the Blessing 2 or the IE300 to the IE 100 Pro, there was a very noticeable loss in image clarity, and they did sound quite a bit grainer by comparison; but that’s not particularly shocking given the price gap between them. Despite not having the resolve or nuance of those higher-end IEMs, though, the IE 100 Pro remains structured throughout, and for its $119 price tag, I think that it provides an adequate level of performance for its detail retrieval capabilities.
Soundstage, Imaging and Layering
Not unlike the IE300, it’s the IE 100 Pro’s spatial qualities that really exceeded my expectations. The stereo imaging on this set of IEMs feels really good, with even distribution across the stage and remarkably accurate left-right localization. Additionally, it had surprisingly good depth and instrument separation; which made for more open-feeling listening experience despite its inherently intimate soundstage.
The IE 100 Pro has good excursive capacities, and it delivers a satisfying sense of punch and slam. As I mentioned earlier, the boosted lower to midbass may play a part in adding a bit of “oomph” in the lows, but either way it made for a more engaging and dynamic listening experience. One thing I did notice was somewhat missing, however, was that percussive instruments and acoustic guitars, for example, didn’t really have much of their attack and strike; so the IE 100 Pro did feel as though it lacked a little of that top-end tactility that I find enhances the presence of instruments in other headphones.
Whether it’s wired, or wireless, the IE 100 Pro is a strong showing from Sennheiser. Whilst it’s not the most resolving IEM I’ve listened to, it’s got good spatial qualities and enjoyable dynamics to properly round out its technical performance. Additionally, it’s got a subtly energetic frequency response with a great tonal balance, it’s very comfortable, and should you opt for the wireless version, you gain a lot of versatility for listening on the move without the need for a dedicated audio player or weird, janky mobile phone dongles.
Unfortunately, at the time of making this review, I haven’t had the opportunity to listen to the similarly-priced and very popular Moondrop Starfield IEM so I am unable to draw any comparisons. However, at $119 for the standalone IE 100 Pro, I think is a fantastic option for audio enthusiasts looking to experiment with IEMs or audio professionals looking for a solid monitoring solution at an affordable price point.
Written by Chrono
Review unit provided by Sennheiser
Watch the video review here:
Discuss the Sennheiser IE 100 Pro Wireless on the HEADPHONE Community Forum here.