Ollo Audio S4X 1.3: Flat Headphones For Podcast Editors That Will Help You Make Better Mix Decisions

As a podcast editor, hobbyist music producer, and overall music lover, I spend a lot of time with headphones on.  I’ve been using my Audio Technica ATH-M50x’s for about 4 years now and have become very familiar with them, but I’'ve been looking for something that is flatter and closer to the experience I get when using Focal Twin6 Be monitors, which I can’t use as much these days.

For disclosure purposes, I was sent a set of Ollo Audio S4X 1.3 open back headphones as part of their influencer program.  I get to keep the headphones, but they aren’t paying me for this video or review, have no say over the content, and won’t see the video or review before I post it.  I am an affiliate and will receive a cut of sales from the links in the description.  The thoughts and opinions in this video are mine alone. I only recommend equipment I use and believe in.

Let’s look at how Ollo describes the headphones on their website:

Studio reference class, open back, dynamic headphones with flat frequency response and USC calibration, made in the EU.


Hand-picked and left / right matched transducers delivering accuracy and instrument separation. (+/-1dB SPL tolerance

32 ohms,

Dynamic Neodymium speaker with 109dBSPL (S4X) 32 ohm output that makes them work with smart devices too.

Replaceable using home tools.


Replaceable earpads

Hybrid artificial leather and velour earpads to control flow resistance around the earpads seal resulting in smoother response in low mids and mids (150Hz-1kHz) perceived as natural timbre on vocals, pianos, strings,...

Fully separated front and back of the speaker for minimal phase cancellation and a more direct sound signature. SoundSeal™


Self-adjusting artificial leather strap

Stainless spring steel powder coated

360 earcups rotation

Strap and steel are replaceable using home tools


Detachable braided silicone cable employing OFC core to ensure minimal signal distortion.

Colour labelled L and R (Left is Black)

Reversible to have the cable coming down behind your back when playing an instrument or in front when producing with a desktop interface.


Unit Specific Calibration plugin included. AU and VST3. Upgrading with the Waves NX room modelling and head tracking available.


5 years limited warranty (Earpads and cable are excluded due to the nature of exposure)

Let’s talk about the build of these.  They’re solidly built with a metal support band and a faux leather strap.  The only issue with the metal band is that any cable noise results in a metallic sound.  All the parts are user replaceable and can be purchased from their website, which is a nice change from most consumer and prosumer headphones.

The thing that had me most interested in these was the flat response headphones and the custom calibration.  As a podcast editor, and DIY audio mixer, I understand the importance of flat monitoring. Our monitoring influences our decision making so much. Flat monitoring from headphones sounds like a lot of marketing fluff, but these deliver.

First, I want to give some background.  I’ve been using my Focal Twin 6BEs for 15 years for mixing music and Audio Technica ATH-M50Xs for editing music and podcasts for the last 4 years.  The M50Xs are a closed back headphone while the Ollo S4Xs I’m reviewing are open back.  All this to say that I’m very familiar with these speakers and how they translate.

Compared to my M50Xs, the S4Xs are more open and neutral with a much wider soundstage.  I could easily hear the boosted high end on the M50s when I was going back and forth. And it’s not a subtle thing.  It’s a night and day difference.  

When listening to music, the wider soundstage of the S4Xs really stands out.  Things that are hard panned are heard much further to the side making the M50s sound like they’re only panned about 45 degrees.  The other benefit to this wide soundstage is how it unmasks details that are buried on other headphones.  It’s like listening to a new mix of songs I know very well.  These headphones are much more detailed with better separation, allowing me to hear things I haven’t heard in these songs before.  

For the podcast editors that are watching, the wide soundstage isn’t going to be important when working on interviews, but would be great for mixing narratives.  You’ll be able to better position your sounds.  If you’re working on 360 projects, Atmos, and the like, Ollo offers the S5X, designed for those needs.  

And while I’m talking about other versions Ollo offers, they have a closed back set, the S4R which are ideal for recording sessions since they minimize bleed.   They have a bit of a mid boost to help with monitoring during the session, so they are best used for recording.  I’ll have links to all 3 in the details.

If you’re working in the music space, the wide sound stage makes these feel more like you’re sitting in the sweet spot between well positioned monitors, except even wider, providing a 180 soundstage with solid center imaging and separation.  You get all the details and the width that other headphones struggle with.  This, combined with the flatter response, makes it easier to make mix decisions without fighting against the headphones.  

For music listening to music, I find these to be great.  It’s been a great pleasure to go back and listen to some of my favorite albums and discover new elements I’d never heard before.  It really is like listening to a new mix.  I saw some reviews on hi-fi sites that call these boring headphones, and I can see why they may feel that way.  These aren’t tuned to make everything sound great.  It would defeat the purpose of flat headphones for mixing.  But after listening to a song with the S4Xs and switching to the m50s, I could easily hear the tuning of them.  I’d describe the S4Xs as neutral.

When I looked at the frequency response graph, I was worried these would be a bit dull, but they are in line with my trusty Focal monitors with plenty of neutral high end.  That dip in the sibilance range is a refreshing change and might initially sound a little dull.  It shouldn’t take long for your ears to adjust.  


Unit Specific Calibration is like Sonarworks custom tuned to the pair of headphones on your head.  It’s a plugin you put as the last effect on your output bus and load the profile.  The effect is quite subtle, especially when compared to Sonarworks.  I’m not hearing the artifacts I do with Sonarworks, probably because it’s having to do a lot less correction.  The USC is a nice bonus but it doesn’t make a big difference.  The only thing I find myself using Sonarworks for these days is for their Translation check.


Overall 4.5

Sound: 4.8

Build: 5

Price: 4


Wide sound stage

Detail & Separation


Build quality



Occasional rubbing noises when moving my head

Overall, I find these a pleasure to work with.  I’d describe them as neutral, detailed, and wide.  I’d have no problems if I had to mix only with the S4Xs and I’d feel confident in my decisions and the translation.  There really isn’t a learning curve to these.

The biggest complaint I have with them is minor.  Since they’re heavier, I’m more aware of them, especially when I’m wearing them for extended periods.  They still comfortable enough for me to wear all day.  They don’t press too tightly on my glasses or put too much pressure on my head.  

The other minor complaint is that if I don’t get them put on just right, I get rubbing noises as I move my head. I haven’t quite figured out the reason, but it’s something to be aware of.  

These sell for $449 USD.  If you buy them directly from Ollo, you can get a free hard case and cable by adding the Affiliate Pack to your cart and using the coupon code “tansy”.  See the details below.  

To sum up, who would I recommend S4X headphones to?