Buy Fosi Audio IM4 Open-Back IEM
Please note that some of the links in my video descriptions are affiliate links where I earn from qualifying purchases. As an Amazon Associate I earn from qualifying purchases.
Intro
If you’re on the hunt for your next pair of IEMs, or even your first pair, Fostex Audio’s IM4 IEMs is pretty unique and worth checking out. It has a unique semi-open back design, houses a 10 mm beryllium coated diaphragm driver paired with a dual N52 magnet structure, dual chamber acoustic design all housed in a premium looking body. It also comes with a high quality oxygen free copper silver plated cable and tons of other gear to fine tune your listening experience. But, how good does it sound and how much sound leakage is there? Well, let’s take a closer look and a big thanks to Fostex Audio for sending this out for review.
Package Contents
In the box, you get the IM4 IEMs along with a two-pin silver plated connector cable. There’s three sets of ear tips for balance, bass, and deep bass listening. And there’s also a zippered hard shell travel case or carrying pouch. There’s brass nozzles, a thank you note along with ear wearing guide, and a manual. The IM4 comes in at around
Design
6.5 g for each earbud. And once these are connected to the cable, that brings it up to about 35 g. The IM4 has a really nice looking design even though it is a bit more minimalist, but it actually feels really good in the hand, feels premium in terms of the build quality. Now, this is a CNC machined aluminum alloy body with an anodized finish. And you can see as I kind of angulated it around in the light, there is a little bit of shimmer going on with this, but it’s not a glossy type of finish. So, it is a matte type of finish. There is good grip and texture there. On the outside, we have that pretty unique look thanks to the open back design with the mesh grill. The side has a two-pin connector port to attach the supplied cable. And we also have the speaker grill here.
Now, do note that you can actually swap this out for the brass nozzles as well. The IM4 houses a 10 mm beryllium coated diaphragm driver in an N52 dual magnet configuration. Here’s what the IM4s look like next to a AA battery to give you a size comparison. The braided connector cable comes in at around 23 g. It’s an oxygen free copper silver plated cable with a 3.5 mm connector and a two-pin
Specs
connectors. Here’s a quick look at the specs. Feel free to pause and review or jump ahead to the next section. To
Tuning
fine-tune your listening experience, you have a couple options. So, one is to use the included ear tips. You have a balanced, bass, and deep bass option. And you also have two sets of nozzles. So, you have the stock aluminum nozzles. That’s going to have added bass with reduced sibilance. Or you can use the brass nozzles, which are going to enhance mids and treble clarity. The
Sound
IM4s are my first pair of open-back, or you could say semi-open-back IEMs, and I really enjoyed my time with these. Now, I paired them with Fosi Audio’s MD3 portable magnetic DAC, which I’ll leave a link down below if you want to check out that review, as well. I swapped out the default aluminum nozzles that came with this for the brass nozzles. And for the ear tips, I stuck to the balanced ear tips instead of the bass or deep bass, because I actually found the bass performance on this to be surprisingly good, even with the balanced ear tips. Bass had a nice, deep, full-bodied feel with solid punch, but it does linger around a little bit longer versus hitting super tight and fast. But I actually found it quite enjoyable.
However, on busier tracks, some of that bass can bleed a little bit into the vocals. Still, it’s not something I would really change. It really hits exactly how I like it. Vocals came through clearly and detailed without becoming sibilant, especially in vocal-heavy songs, where they felt front and center and fairly immersive. But on busier tracks, like I mentioned earlier, the bass can creep in a little bit and pull vocals slightly back. The treble had enough detail and sparkle to keep the listening experience enjoyable without sounding fatiguing. On most songs, nothing really sounded overly harsh or sibilant, but personally, I would prefer a little bit more presence in the upper end.
I found it pretty easy to hear smaller details from instrumentals, along with little background nuances in tracks. There was also a good sense of stereo placement and spacing between instruments, keeping music open versus sounding compressed or too congested. Overall, I found these to deliver a really enjoyable listening experience with a good amount of detail and satisfying bass presence. The
Sound Leak?
microphones are on 33 cm away from my head. So, I’d say once you hit about 25% volume, there is going to be some sound leakage. Now, do note this is a very quiet room with little to no ambient noise. In most environments where you’re on a bus, on a subway, or in a busy coffee shop or restaurant, there’s going to be enough background or ambient noise to really kind of drown this out. But, once you start getting to about say 40%, 50% volume, there will be significant enough sound leakage where people who are pretty close to you will be able to hear it. But, again, at 50% volume, this is already plenty loud, maybe even a little bit too loud for me. In terms of
Comfort?
comfort, I was easily able to wear these for hours at a time with no [music] issues. And even with the large ear tips on here, I could definitely feel they’re in my ear canal, but it never felt like it was being stretched out, and it never felt uncomfortable. And I didn’t have that feeling of heat build-up or any type of fatigue while listening. Again, thanks to that open or semi-open type of design. So, overall comfort just really good on these. So, I’ve really enjoyed
Recommended?
my time with the Fosi Audio IM4 IEMs. And I’d say, if you’re on the hunt for IEMs, you’ve not tried open-back or semi-open back, these are a great place to start. There’s a ton of IEM options out there, but for the price that these cost, around $99 US at the time of this video, I think it’s pretty good value. You get excellent build quality, the cable’s a high-quality cable, you get a ton of gear in the box to really fine-tune your listening experience. It’s pretty good value. I’ll leave links down below if you want to get your very own pair. And if I have any type of coupon codes, I’ll leave those down below as well, along with my review of the Fosi Audio MD3 portable DAC, if you’re interested.
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Buy Fosi Audio IM4 Open-Back IEM
Please note that some of the links in my video descriptions are affiliate links where I earn from qualifying purchases. As an Amazon Associate I earn from qualifying purchases.