Ollo Audio s4


Reviewer at Soundnews
Pros: Amazing build quality, hand-built with lots of care for the environment
Great tonal balance! Almost flat frequency response
Good speed, impact and slam
A high level of detail retrieval
Good transparency, low distortion levels
A sharp outline of the notes, good texture as well
A very attractive price point, Recommended!
Cons: Up-front sounding
There is a dip at 9 kHz but at a short frequency range

Researching headphone manufacturers from Europe I stumbled upon OLLO Audio, a fresh Slovenian company that is making hand-made headphones. As of right now they have only two dynamic driver models: HPA S4 (S4 from now on) – the open back one and HPA S4R (S4R from now on) - the same headphone but with a closed-back design and if you would like to have a one-of-a-kind S4R, OLLO can put a custom laser-engraved logo on them.

My curiosity levels, as usual skyrocketed, I told myself I need to hear those. One month later and I had the open-back S4 on my desk.

I am quite impressed by the Slovenian tinkering skills, I already made a review for a boutique headphone amp manufacturer from the same country called Erzetich Audio and I already know that music is somehow passing though their veins, this is surely not a coincidence.

OLLO Audio is describing their S4 and S4R as studio monitoring headphones that should have a linear performance from the lowest bass to the upper treble and is ensuring that no DSP or EQ corrections are needed when listening to them. I will of course test all those claims, will measure them myself and will compare them to other candidates.


Unboxing Experience

OLLO S4 came in a small card-board box, upon opening the box a fresh smell of wood and paper hit me straight away. It was clear to me that OLLO is using only environmentally-friendly materials. The box is free of any styrofoam or any type of plastics, S4 came wrapped in a wide sheet of paper, the cable was wrapped in paper as well, you are greeted with a nice message from the company.

What was really unexpected is that every single pair of S4 or S4R is coming with its own measurement chart, even very expensive headphones nowadays do not include measurements in the box and that is sad. Way to go OLLO, I really like your approach!


Build Quality and appearance

Design wise I find them a little bit unusual and they will surely stand out from the crowd. I find them on the heavier side since the ear-cups are entirely made from thick walnut wood. The headphone structure is made out of stainless steel and the headband is made our faux-leather. Their adjusting mechanism is exactly like that of Meze 99 Classics and Empyrean and this kind of system is the easiest to use. Just put them on your head and it will automatically adjust to your head size. The head-pressure is a bit higher than normal, as a comparison think of fresh out-of-the-box Sennheiser HD650 or HD660S, well S4 is almost like that, but clamps your heard just a little bit more.

The ear-pads are made out of faux-leather as well with a red colored acoustic foam that was put there to absorb excessive treble energy.

The ear cups are just moderately big, so S4 and S4R can even be used as a portable headphone or traveling around since it is not that big or hard to drive.

The exact ear-cup diameter is 90mm, inside them a 50mm dynamic driver is mounted by hand that was tuned for a wide frequency range of 20 Hz to 22 kHz with a flat response design, will see about that really soon.

I have normal sized ears and yet for me S4 can be barely considered over-ear since there is close to no space inside the cup. Folks with rabbit sized ears could have a problem with them as they might transform into On-Ear headphones, add a higher clamping force and not a single carrot can save your listening session.

S4 is of course using a detachable cable that looks very DIY to me (in a good way), to the ear-cups it will attach using 2.5mm plugs and it is terminated with a 3.5mm jack, inside the package there is also a 3.5mm (1/8”) to 6.35mm (1/4”) adapter. The cable is free of any microphonics and has a sturdy mesh on the outside that should resist few good years.

In terms of build quality S4 is just screaming high-quality, as every single piece of it is made out of stainless steel, walnut wood and faux-leather and the best part is that every single part of S4 is replaceable with home tools. When I am holing S4 in my hands I feel them really sturdy, think Beyerdynamic sturdy, I know dropping them occasionally should not damage anything inside since I already stepped on the cable and the headphone flew and hit the floor pretty hard – they worked flawlessly after this incident, nonetheless kids please don’t try that at home.

There is also a very nice faux-leather pouch, carrying them to work and back should not be a problem, with or without the pouch S4 is made to last a life-time and I already feel the love and soul OLLO Audio put into making these.


Technology Inside OLLO S4

Creating S4 and S4R OLLO Audio used matched pairs of 50mm dynamic drivers. The impedance is a low 32 Ohm, but no sensitivity numbers were given. From my own experience S4 are not that easy to drive and definitely needs a bit more power than the 32 Ohm Meze 99 Classics or the 32 Ohm Sennheiser Momentum 2.0 Over-ear. Power requirements are about 4 db lower than the Sennheiser HD660S, doing my math I presume a sensitivity of around ~99 to 100 dB per 1mW of power, it means it can be driver by portable sources as well.

I really like that OLLO choose this 100% symmetrical design, any ear-cup you want can be your left or right earcup, the only L and R markings are on the cable itself. The same symmetrical design approach I’ve seen on the full-sized Meze headphones, I personally dig it.

I think it is time to have a long listening session.


Sound Performance

I. The Good

To fill some of my void I listened to Staid – The Singles, the last four live tracks from the recording are special to me and a very good example of how a live recording should sound.

From the first notes of Everything Changes I knew I am listening to an airy presentation with a good layering. I am impressed by the very clear cymbals, by the hit of the drum sticks and by the voice that flew far away fading just at the right time. I really like that nothing from the mix is fighting for the prime-time, nothing particularly stands from the crowd, yet everything is at its place never outdone or overshadowed. Overall, HPA S4 sounded transparent on this track without a hint of veil or muddiness that is present on the Momentum M2.0 and even on Meze 99 Classics that costs a little bit more.

Switching the pace to a faster S.O.A.D – Toxicity I was pleased to find a really good timing of the driver. The “mashing effect” and an unpleasant resonance of the Momemtum M2.0 on faster music is nowhere to be found, S4 has speedy transients and overall quite good information retrieval.

The more I listen to acoustic music on the S4 the more I realize they have just a small emphasis on the upper bass and over the midrange area as more often I feel this slight warmish tint with an uplifting musical performance.

OLLO Audio is supplying a frequency measurement but is applying a 1⁄6 smoothing to the chart. I on the other hand I measured their raw performance, their waterfall and later on I applied a 1⁄12 smoothing that I feel is representing their true nature.



I used a Matrix Audio Element X as the source and Bechmark HPA4 as amplification, MiniDSP E.A.R.S as the measurement rig for the OLLO S4.

I used the headphone compensation for flat EQ (HEQ) for this particular EARS serial number, I ran multiple measurements tests and here are my final results. The first chart is the RAW measurement.


There is a very small deviation of about 1 to 2 dB between the drivers up to 200Hz, that is more than OK, all-in-all the right and left driver is matched and even on the treble area the matching is quite impressive. As I presumed the upper-bass and the midrange is slightly boosted for this natural and life-like presentation. Our own brain is boosting the midrange so we can hear it clearly, so I think OLLO S4 are quite flat with a small drop in the sub-bass area and a very short but nasty drop at 9 kHz.

OLLO S4 SMoothing.png

Applying a 1⁄12 smoothing is looking very similar with the measurements of the OLLO Audio and if I am applying a 1⁄6 smoothing, they both look identical. I don’t know what OLLO used but I presume an MiniDSP EARS measuring rig as well, they just look impressively close to each other.

Waterfall plot shows a longer decay of the sub and mid-bass, for a dynamic driver that is normal behavior, closed-back dynamic designs are looking much worse in this department. As it can be seen the biggest emphasis is in the midrange department that will infuse just a little bit of joy and naturalness while listening to music. Of course, the 9kHz dip is also visible, a very short 10dB deviation in terms of frequency range.

OLLO S4 Waterfall.png

All in all, OLLO S4 are measuring much better than my own Sennheiser Momentum 2.0 and Meze 99 Classics and about on the same level with $500 Sennheiser HD660S. I think they are already showing great potential of how they might sound. Measurements can’t really tell how clean, detailed, transparent or how wide they might sound, so from this point on my subjective opinions will follow.

S4 have a seductive and inviting character, somehow calling for another track. Musical sounding some might say, as a result S4 can be listened for a very long time without listening fatigue.

As another result, dryness is never present, S4 choose to be full sounding with some meat to the bone. Listening to simple orchestral or acoustic music with lots of musical instruments around me it is clear as the blue sky that S4 was just made for this kind of music. Everything sounds clear, very outlined, having a sharp texture. The voice in the background sounds really smooth. Even Jazz and classical is a delight on S4. If acoustic, classic, jazz or folk is your thing then S4 should be a good musical companion.


II. The Bad

S4 have a pretty good left to right separation but I don’t consider them really open-wide sounding. Soundstage size is almost on the same level with HD600/650/660S family of headphones and will not Wow you with out-of-your-head experiences. S4 has a small to medium size soundstage and on some aggressive rock can be even up-front sounding. Some might like this kind of performance, some might not.

Depth performance is directly tied to the soundstage and airiness, so again depth is pretty good but it isn’t impressively deep reaching and the notes are decaying sometimes faster than how I’d want to.

Mid-bass is impressively deep, layered, sounds pretty clear too but the sub-bass area is just moderately good. This is really normal behavior for open-back dynamic driver headphones, not a single one is offering a better sub-bass performance. Anyway, it should be mentioned, the 20 Hz hits on The Prodigy – Invisible Sun are not tickling my ears like how much more expensive Sennheiser HD820 or Hifiman Arya are doing. I hear a weaker energy in this area and a weaker slam as well.

Although there is just a very short dip at 9 kHz – the high treble region, some tracks that are emphasizing exactly this area will not sound as impressive and as biting, sharp or outlined. It is like a tiny portion of your treble energy is missing. I am air guitaring around and I am expecting those triangles, cymbals, hi-hats and tambourines to hit me with layers of information but that is not really happening. Again, this happens only on some tracks and it was done for a relaxed music listening.


III. The Great!

Oh man, people know that at around $500 is hard dethroning the legendary Sennheiser HD600/650/660S, as anybody who is asking me for a musical headphone in that price range more often exactly those headphones will be my recommendation.

However, I will add another headphone to that list as S4 is having some additional traits that HD6xx is just not doing as good.

First of all are the leading-edges of the notes, the outline of every note. On Sennheisers you hear them but not impressively clean or outlined, a little bit fuzzy somehow. S4 is having those clearer, more outlined, sharper start and end of a musical note if you will. As a result, the overall presentation is a bit clearer on OLLO S4, sounds are sharper and every note is really more outlined. Switching back and forth between them this is the first thing that will hit you.

Another cause and effect are of course the timing and transient response as every note will hit you a tad harder with a bigger force. S4 out of Benchmark S4 are punchy sounding and have the right amount of slam, speed and impact. At this price point they perform admirably in this department. Did I hear a better slam? Hell yes. At this price point? Hell no!

To counter balance the sub-bass deficiency OLLO gently boosted the mid-bass that is doing its magic on the right music. For the past few weeks I am quite impressed by the Infected Mushroom – Guitarmass track that is impressive in terms of sub-bass, mid-bass, layering, slam and speed of delivery. All of those points are impressive on S4, except for the sub-bass area that loses a bit of oomph and slam. OLLO S4 will sound incredibly good with electronica and rock tunes, actually I listened mostly to this type of music on S4, can’t get more of it.

Powering them with Benchmark HPA4 I have about 45 dB of headroom left, on the mighty KECES S3 I am left with about 60 dB of headroom. Even portable sources are performing admirable with them.

The low power FiiO M6 sounded fine (but not mighty fine), after some proper evaluation, portable sources are losing a bit of driver control, speed and impact but overall enjoyment level remains intact. People are driving their HD660S with portable sources so S4 should not pose a problem to those folks.



Meze 99 Classics (€309) VS OLLO S4 (€290)

Both have the same symmetrical design, both have walnut ear-cups and stainless-steel headphone structure, Meze have bigger ear-cups and a lower pressure on my head. 99 Classics is a closed design and S4 is open-back.

In terms of sonics Meze have a bigger emphasis on mid-bass and midrange in general, so it will sound warmer, fatter and even juicier. However, the tonal balance is not ideal since a flat FR is out of the question. Meze are also a bit easier to drive and can be powered even by smartphones.

S4 has a better grip, faster speed, impact and the slam is tighter, not as loose sounding as the Meze. S4 also has a better outline of the notes, every sound is just sharper on it. For pure musical enjoyment and relaxation Meze is doing that better. S4 is flatter but also truer to the recording, with better diaphragm control.

Hard to tell which one is better; they both have their magic moment.


Sennheiser Momentum M2.0 (€300 at first, €200 right now) VS OLLO S4 (€290)

Build quality wise both are fine, Momentum have leather headband and ear-pads, S4 has them from faux-leather, Momentum are not as heavy and even easier to carry due to their folding mechanism. In terms of looks I like them both. Momentum 2.0 is a closed-back design, S4 is open-back.

When it comes to sonics Momentum has a big emphasis on midrange and mid-bass and sacrifices a lot of treble energy. Momentum is warm, full bodied sounding. They are never tiresome in the long run and are sounding quite engaging and fun. Their biggest problem is the soundstage that is very in your head, on-stage presentation. They are also loose sounding, especially with fast electronica.

S4 is better on almost all key aspects: they offer a higher detail retrieval, a better pin-point imaging. The sound is more transparent, bigger as well. S4 don’t have an impressive stage, still they sound grander and wider spread. S4 is of course more controlled, has a better grip over the drivers and hits harder as well.

S4 is in a higher league and that was felt from the start


Sennheiser HD660S (€499) VS OLLO (€290)

HD660s are made entirely from hard plastic with a metal structure and mesh, however uses much bigger ear-pads so the conform level is higher as well. HD6xx have their legendary status already, so no introduction is needed.

In terms of frequency response both are very close and I can’t fault any of the two. Both are quite engaging from a powerful headphone amp. S4 is easier to drive, HD660S can be used only with powerful mobile solutions (a powerful DAP, portable headphone amp and so on).

HD660S are sounding airier and just a hair wider and deeper and that is apparent mostly with high-quality live recordings. With HD660S you can follow a note from its inception to its decay, S4 is doing that faster. As a side effect the notes have a bigger void space between them, so overall HD660S in an airier sounding headphone.

On the other hand, S4 is a hair faster, slams harder and you can clearly hear the leading-edge, the outline of the note that is sharper. It is like boosting the resolution of in image. In terms of detail retrieval both are on the same level, on the right system both will reveal small nuances and micro-details.

Sometimes S4 has a little bit more treble energy, sometimes HD660S tickles my ears with more treble detail, so it’s a tie on the treble area.

Overall, I am splitting hairs since both are great sounding headphones, HD660s are just wider and deeper and S4 has a better driver control and a better slam. Pick your poison.



If a narrower soundstage and smaller ear-cushions will not put you off, OLLO S4 will reward you with a flat frequency response, just a tad towards a natural and musical presentation with a very good grip and control over the headphone drivers. I enjoyed my time with them starting with classical music and finishing with some metal tunes, everything sounded fine to me without obvious flaws.

The headphone construction is built to last and just in case something fails, don’t worry too much as any part is replaceable with home tools and you will be back to music listening in no time.

For a first attempt, OLLO Audio did a remarkable job and at that price is hard complaining about anything at all. The best part of this incredible package is the price, they were €349 at full price, but you can get them right now at a discounted price of €290 from here. For this environmentally friendly, build to last construction and linear sound-performance I think it is a no-brainer purchase.

  • Amazing build quality, hand-built with lots of care for the environment
  • Great tonal balance! Almost flat frequency response
  • Good speed, impact and slam
  • A high level of detail retrieval
  • Good transparency, low distortion levels
  • A sharp outline of the notes, good texture as well
  • A very attractive price point, Recommended!
  • Up-front sounding
  • There is a dip at 9 kHz but at a short frequency range
  • DACs: Matrix Audio Element X, Matrix Audio X-Sabre Pro, KECES S3, Burson Swing
  • Headphone amps: Benchmark HPA4, Aune S7 PRO, Erzetich Bacillus, Headamp Gilmore Lite Mk2
  • Full-sized headphones: OLLO S4, Hifiman Arya, Quad ERA-1, Sennheiser HD660S, Momentum M2.0, Meze 99 Classics
  • Loudspeakers: KEF LS50W
  • Interconnects: QED Reference XLR, Aune AL3 XLR
  • Power Cables: Isotek EVO3 Premier
  • Balanced Power Conditioner: PLiXiR Elite BAC 400, KECES BP-600
Great review!! So, are these on-ears or over-ears. From the pictures the size of the cushions seem to be somewhere between :)
  • Like
Reactions: DarKu
Thanks! You've said it better than myself, somewhere in between. They are just barely over-ear for me and on-ear for one of my friends. The internal cup space is a bit bigger than that of Sennheiser Momentum 2 and a little bit smaller than that of Meze 99 Classics (hopefully that helps)


Headphoneus Supremus
Pros: -sound quality on general
- exceptional build quality
-handmade luxury item
Cons: -dark(ish) sound is not for everyone
-small earpads
-occasional bass honk
  1. Edit: Since the price of S4 is currently only 289€ I've updated the rating from 4.5 to 5. I also added proper fr measurement I did and added some comments about the perceived neutrality as measurements don't look neutral.

  2. Olloaudio is a new headphone manufacturer from Slovenia. Product that sets them apart from others is their BSE(body sound experience) system that is a tactile subwoofer pillow which helps the user to feel the bass instead of just hearing it. However now I'll be focusing only on their hps s4 headphones. These headphones were received from ollo via their endorsement program. I got a 50% discount for publishing my honest opinion on the headphones and I will receive no further compensation.

  3. Introduction

    Ollo Audio HPS S4 headphones

    Price: 349e
    Speaker size: 50mm open back design
    Frequency range: 20-22kHz flat response design
    SPL: 112dB hearing threshold
    Impedance: 32ohm
    Ear cups outer diameter: 86mm
    Ear cups inner diameter: 70mm
    Ear cups material: Walnut
    Headband material: Stainless steel and Italian leather
    Ear pads size: 90mm
    Ear pads material: Acoustic foam, extra elasticity artificial leather
    Cable termination: detachable 2m long Y 2.5mm mini jack
    Connector: 3.5mm jack with adapter to 6.3mm jack
    Servicable: Every part of HPS S4 is replacable with home tools

    Gear used in this review:

    Hegel hd10
    SPL phonitor
    Topping NX1
    Audioquest dragonfly black v 1.5
    My diy PC
    OnePlus 6

    Music of various genres with Spotify premium or flac from pc. Pretty much everything from dimmu borgir to paw patrol theme song.

    After receiving the headphones allmost two months ago I've been using them as my main headphones. It took me a long long time to get a proper impression because before ollo's I had been using mostly sennheiser hd800, Grado sr325i and akg k701. All known to be bright headphones. Ollos have more of a darker tone so it was quite a change.

    Before talking more about ollo's tonality, lets take a look at the headphones.

    Build quality:

    There is no way around it. These are exceptionally well built headphones. Everything except the pads is made of wood, metal or genuine leather. Housings are handcrafted walnut. They're not polished or treated to shine. Headband arch is stainless steel, back of the housing is made of aluminium and so is the baffle/driver cover. Headband is italian leather and earpads are some sorth of fake leather with microsuede like texture. I like the the looks. It is fancy enough but also looks like a robust studio equipment. Something that is ment to be worn and used instead of just being gazed upon.

    What I particularly like is the cup design. Instead of rings made of wood Ollo's uses a solid piece of wood in which the driver is installed. There is no seperate mounting baffle for the driver and wood part is not just a ring. I think this design will add to durability a lot. Wooden rings are known to break when the wood dries too much. I think that will never be an issue with this design. In the picture below you can see how the headphones are built and how the driver is inserted. The black ”baffle” on top of the driver is aluminium.

    The headband is quite normal self adjusting headband. Similar to the likes of used in many AKG headphones for example. The shape looks weird in pictures but it is soft and adjusts to my head perfectly. Only thing I can fault the headband is that they have a small area underneath the band that is sown together.

    I thought the stitch was there because the headband leather had a hole in it but according to Ollo that is how they fix the elastic inside. It does not look good but of course nobody can see it underneath there. It is a small thing but I hope they come up with a better design in the future.

    Headband arch is made of steel. It has a durable feeling to it and I don't think I could break it even if I tried. Bad thing is that the arch is highly microphonic. Microphonic is kind of an understatement...if you plug the arch while it is on your head you get ringing that lasts for 15 seconds! Not that it would affect anything on a normal listening but on principle alone one would like the housing and the headband to be silent and free of possible side noises. I asked Ollo about the headband and according to them the headband does not affect the sound quality. They had actually done measurements about it so propably I'm worried over nothing.

    Cool thing about the headband arch is you can hang them everywhere. Smallest headphone holder ever:

    Pads look a bit cheap in contrast to other parts. They're made of artificial leather but the material is nothing like traditional pleather you get on most headphones. To me the pads feel more like microsuede than leather. I'll talk more about the pads later.

    One thing worth nothing is that as stock S4's come with red fabric cover that is there to tame the highs. Nice and easy way to tune the headphones.

    Headphones have a dual entry Y-split 2.5mm connections with 3.5mm connector at the end.

    Dual 2.5mm is a smart move. Getting replacement cables is easy since sennheiser hd700, oppo, velodyne, denon, audioquest etc use the same connectors. It seems to me it has become a industry standard over 3.5mm dual connectors. Cable itself is very basic. Nothing fancy. Metal plugs with vowen plastic cover on cable and rubber after the split. You can get one for 20 bucks on ebay. But it works and I'm glad cost of headphones comes from other things than from a fancy cable.

    All in all these are exceptionally well crafted headphones. Pads are not fancy and headband arch resonates sound but besides that these are one of the best built headphones I've seen regardless of price range. It's a nice mixture of luxury materials with a design suited for professional use. Rugged but beautifull.


    The self adjusting headband is propably the most comfortable I've ever encountered. Not that there is anything particularly wrong with the designs used by hifiman, akg or audio-technica but in my opinion Ollo is a step above. The headband looks weird when not worn but because it is so soft and bendy it perfectly adjusts to ones head shape. There is zero pressure on the top of the head.

    Clamping force is mediocre or slightly loose. I have a medium small- medium sized male head. That is no measurement, but you get what I mean. I would personally prefer a tighter fit. These don't fall off when doing some basic home choirs but If I tilt my head fast these might fall off. Luckily steel design allows users to bend the headband to their preferred grip.

    The earpads are where the problems begin. Like I mentioned before I don't really feel that earpads are on par with other design look wise. Unfortunately they're not that comfortable either. For my somewhat pointy average sized ears these are quite good but after 30 minutes or so I have to adjust them. People with larger ears will have bigger problems with these. These are no way on-ears but one might have to tuck the ears in a bit which is not ideal for comfor nor for the sound quality.

    I contacted OLLO and asked why they went with seemingly subparr earpads. They said they tested 20-30 earpads and these were the only ones that sound good enough. I believe that. I tried bunch of other pads. All velour pads are a no go definately. HM5 pleather pads sounded decent, other pleather pads collapsed soundstage or otherwise affect sound in negative way.

    The pads are not absolutely horrid but at $400 standards are quite high. However some of the competition does even worse. Onkyo a800b is less comfortable and one rarely mentions comfort and grado foam pads in a same sentence. In a way I even find Sennheiser hd800 to be less comfortable than Ollo's. Hd800 is just so huge that it feels like I have dinner plates on the side of my head.

    I hope that in the future ollo figures out how to maintain the soundquality and introduce headphones with more comfortable pads.

  4. Update: Here is a fr measurement with ollo and audioquest nighthawk carbon in same picture. I chose nighthawks because remarkable tonal resemblance.
ollo_vs_nh.jpg It is obvious that S4 has elevated bass and as such not that neutral. Nighthawks have this overly thick sound and lower midrange gets affected by bass. This is not the case with S4's. Ollo's have more upper midrange presence which adds to clarity alot.

According to ollo these were designed to be ”neutral and brutally honest”. According to Ollo hd650 is closest tonally to shp s4 than any other headphone but sennheisers have slightly brighter treble. I think people who like audioquest headphones might also appreciate the ollo sound.

That pretty much describes the soundsignature. To my ears OLLO's are very natural sounding headphones with hefty midbass and somewhat dark tone. There is never any sibilance.

I can't help to feel I could use a bit more energy at top. It is all there but I'd just like more sparkle and air up top. On occasion these feel kind of closed in. On the other hand I never feel that way when listening very good quality recordings. Usually unforgiving headphones are the brighter ones. Ollo's have a fresh perspective on that. For example meat loaf: bat out of hell, is far from being an audiophile approved masterpiece. I'ts a muddy album with boosted highs. Bright headphones make it sound lively but ollos just reveal the bad quality underneath. With S4's highs are more in line with the rest of the sound spectrum revealing how bad it is all done. Meat Loaf is just one example. These completely ruin a lot off my favorite music... Old Iron Maiden etc. And that is a good thing for a headphones designed for studio use. Not so good thing for using these headphones for sheer music enjoyment.

Soundstage is mediocre in size but it is very proportionate. Everything is imaged very well in space. Many headphones have excess width with lacking debth making them sound unnatural. OLLO's have very well defines soundstage allbeit a bit small. Since these were designed for studio use I think this kind of presentation comes in handy when switching from monitors to headphones. The superstereo effect is one of the major downfalls on headphones and it makes sense to have it minimized on a headphone like this even if it has it's drawbacks. Unfortunately these are not resolving enough for good vertical positioning. I must say though that in my experience no headphones are in this price range.

Sonically S4's biggest downfall is the bass. On one hand it is linear and well extended. Very well extended for an open back dynamic headphone. It does not have the "grip" planar's have but for a mid priced dynamic headphone it is very impressive. Unfortunately there are time I feel bass becomes a bit blurry and honky. I think it is just some particular frequency that triggers the effect because it does not seem to happen with any particular genre of music nor is it dependent on how bassy or fast the music is. It is by no means an persistent issue, just something that happens every once in a while and I found it bothering.

Without something to compare headphones with, it is just all words without substance. So I compared Ollo's to some of the open headphones I have at the moment.Ollo S4 vs Onkyo a800

Well regarded and similarly priced onkyo's are a good headphones to compare. Both are open back and easy to drive 32ohm dynamic headphones. Onkyo's are considered by many to be an upgraded version of well known Philips Fidelio X2. Both headphones are made by Gibson so it does make sense. Onkyos are a very nice headphones indeed. However I can't help to feel that compared to Ollo's Onkyo's have somewhat distant sound. I don't mean a large soundstage with back row presentation but something that is just a bit unnatural with a800. It is kind of like sound is coming from a tunnel.

Bass performance on both headphones is very good for open headphones but I think Ollo's are still step ahead here. On the subbass region Onkyo's start dropping quite drastically as Ollo's just keep on going.
Onkyo's are not bright headphones but they definately have more treble presence than ollo's. I find onkyo's sound a bit unrefined up top compared to ollo's.

For someone looking for neutral but with fun treble tilt Onkyo is a better choice but if one prefers more natural midrange and linear bass Ollo's are obviously better headphones.

Ollo S4's vs AKG K701

K701 can be had for 150€ these days and along with hifiman he400i I think it is propably the best bargain one can get these days. AKG's sound cleaner on midrange compared to Ollo's but they lack the natural heft Ollo's have. Particularly piano music is a lot more impressive on Ollo's. Ollo's can't match the huge soundstage of AKG's nor the detail retrival qualities. K701 is known for lacking bass and it is obvious that Ollo's have hands down better bass performance. Ollo's also sound more natural on highs, K701 tends to be bit grainy at times. I think Ollo's are step above K701 but considering the low price of K701 it depends on ones preferences if Ollo's are worth the extra money.

Ollo s4's vs Beyerdynamic DT880 (2003)

Considered by some to be one of the finest headphones beyerdynamic has ever produced, old 2003 version of classic dt880 is not a headphone to be neglected. It is indeed a fine headphone offering a larger soundstage than Ollo's. Beyerdynamic has a clean, clear sound and Ollo's do sound quite murky in comparison. It is quite the same as with akg 701. It is also same in a way how Ollo easily outperforms beyerdynamic in the bass department like it did with AKG's. Same goes for the midrange. Ollo's have mids that integrate to highs so well that headphones like k701 and dt880 sound kind of like two way hybrids with bad crossover implementation. Then again we have the price issue and I must say these old dt880's are no slouch when that is taken in consideration. However it is clear that Ollo s4's is the better of the two.

Ollo S4 vs Grado sr325i (gold 50th anniversary edition)

I'm quite of a fan of these Grado's. I've had some experience with their headphones and I don't think this old sr325i is much worse than RS2e I had couple of years ago. I never had the change to compare the two side by side but that is just the feeling I have, so take it with a grain of salt.

Anyway... Grados are a formidable opponent to Ollo. Grados have very fun punchy bass, it is not as well extended as Ollo's but it is more fun. Also the bass on grados never gets honky like I've mentioned is the case with Ollo. 10 point's for grado!

Both have exceptionally beautifull midrange. Presentation is different but both sound just great. Compared to akg and beyerdynamic, Grados sound more beefy, robust. Very similar to Ollo's in that regard.

Sr325i's are often regarded as brightest off all grados. It makes them fun, in a way. However if one tries to be objective it must be said that highs on sr325i's are way over the top, ridiculous even. It is all fun, cool and exciting until you listen to Metallica: carage inc or something similar.

Because of the excessive highs Grado's sound airy but they can't really match the soundstage of Ollo's. Width is about the same but grados have little to none soundstage debth.
So yeah... Obviously Ollo's are the better of the two.

Ollo S4's vs Sennheiser HD800

This comparison does not make much sense because of the price difference but since all the headphones above were cheaper why not compare Ollo's to a more expensive one.

It is obvious that hd800 is a step or two above ollos. HD800 sounds so clear and effortless that Ollo's can't match that. Ollo's have an edge in overall tonality. HD800 is in a sense faulty headphone with it's treble peaks etc. Ollo's are more consistent and...well, "neutral". Ollo's also have better bass extension. Comparing these two would be like comparing hd650 and hd800 so I won't go any further.


Ollo S4's are headphones with exceptional build quality with some comfort issues. Similar sound quality might be available for less $ but without the materials and craftmanship that is invested in these headphones. Ollo's have become a valuable reference headphones for me and I understand why many professionals love them.
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? at the 32ohm whats the max power load that they can take my shciit magnus puts out 5watts at max under the balanced output is that to much for these ?