OLLO Audio HPS-4

a modern mixing-headphone with "linear" to "accurate" frequency response is a dream - or (at least) very valuable tool for mixing engineers as producers. Not less then this is what the small company from Slovenia - OLLO Audio offers with their new approach to engineering headphones and states in their targeted marketing ads as on their website.

after some recherche and discussions in a german bulletin board about existing tests or validated recommendations for audio geeks and gearsl*** i decided to take this "adventure" and test the headphones against my arsenal of Sennheiser HD650, a line of AKG from old 120 up to AKG 712 pro.

after registering as a "endorser" to get a discount on this adventure, paying a PayPal invoice to OLLO some friendly guy from OLLO contacted me for shipping details and - around a week later - a small package arrived my studio desk. now, a week later, i used it intensively for different studio tasks during a production of a song (sound design as mixing,pre-mastering, A/Bing etc.) while swapping against some of my existing headphones which i used in the past - for comparison and getting a relative "ground" against HPs i have by far more experience with (Sennheiser HD650 and AKG 712 pro - beside a bunch of other AKGs for instrument and recording monitor usage).

official parameters:

  • Speaker size: 50mm open back design
  • Frequency range: 20-22kHz flat response design
  • SPL: 112dB hearing threshold
  • Impedance: 32ohm
  • Ear cups outer diameter: 90mm
  • Ear cups inner diameter: 70mm
  • Ear cups material: Walnut
  • Headband material: Stainless steel and Faux leather
  • Ear pads size: 90mm
  • Ear pads material: Acoustic foam, extra elasticity artificial leather
  • Cable termination: Detachable 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 

first impressions:

it is a complete set consisting of:

  • headphones
  • cable with small stereo 3,5 TRS jack (with screwing)
  • 6,5 TRS jack adapter (golden surface)
  • a robust bag for transportation
  • a individual REW SPL graph of measurement

On top i've found (partly hand drawn) warnings how to not handle the headphones to avoid any damage. i.e. pressing the earcups onto a table or flat surface seems a bad idea as the air pressure could damage the membranes inside.


the optics and fabrication of the HPS-4 is "simply" top studio quality.

the HPS 4 comes as "standalone headphones" with unpluggable cables. this is nice if they got broken in any way in the future - even if the cables are of a high quality and feel professional. the cable plugs are sitting / locking strong into their fittings. after connecting the cables into the earphones, i look for any "left/right" signs and after a minute or so i've found them printed in grey on the silver cable plugs, which are not so easy to read in a darker studio environment. 

since many years i love my HD 650 for their "linear" (at least around the mids) sound, but i less like the "feeling" on the head after more then a hour, because of the strong pressure against my heads sides. the AKG 712 pro is "very soft" compared to the HD 650 and gives me a feeling of "to much of soft", more ideal for helping to get into sleep. the OLLO Audio HPS-4 is light and soft and it does not disturb in any way even after a few hours of usage / work. it is easy / fast to "set up" and "take down" without any hassle.

the only thing i surprised me a bit: when touching the steel bows of the HSP4 by hand (if weared) they created a sustained  "bong" around 200 Hz - but this could be damped with some tape, plastic hose or similiar. i will test if that has any influence in any form of "interferences" or similiar.

OLLO HPS-4 set


headphones are like glasses / microscopes - they easily give a very to "over-detailed" picture of "what's going on" to human brains, so by theory and practice there is no "really linear" headphones, as their curve depend from the head of the listener and other individual factors. but good headphones can do a lot to "nearify" to this target. 

with the HPS-4, OLLO Audio did that very far and - at least for me - best under all of my headphones. the small unlinearities (at least on my model) are more helping then disturbing mixers at work.

while using the OLLOas my future main headphones, i would further use i.e. my HD 650 for very critical works / checks in the mids areal - similiarto my two sets of monitors setup with "broadband" Adam S2V and Yamaha N-10Mfor the "mids" (as many studios use).

the HPS-4 is way more "open" to the edges of the spectrum - bass and highs - then the HD650 (without any "bathtubecurve" as on "top consumer headphones"). switching from the HD 650 is like "opening the window".

bass stuff is much more detailed to hear and work at while no loose of precision. similiarin the upper highs / top end. the mids are very nice to, but possibly due to the "microscope effect" my ears get bit more details on the HD 650 - where no distraction from other frequency areas affect.

the broad frequency range is more comparable to the AKG 712 pro, but the HPS-4 provides much more of transient signal then the AKG before clipping / disturbing "stuff around" in the sound image. 

the HPS-4 delivers more "punch" then any of my other headphones (possibly trough the small "shift" between 100 and 250 Hz) plus more true to transients with bass.

the HD650 is more a "eyeglass" for the "critical" 3-5kHz area (for what i.e. many studios have i.e. Yamaha NS-10Mas secondary monitors) while the OLLO HPS-4 goes much deeper in bass while opening it for more exact / critical decisions there. similiar on the top end.

while the OLLO is a very nice mixing / work tool, especially for more modern / current music styles where bass and transients are getting much more attention - it is capable to suite critical audio consumers to "HIFInerds" too. it is fun to hear music on as on very good studio monitors in a well treatened room.

bow sound:

On my model, i got "bow sound" up from 114 Hz and a few harmonics / "side bands" up to roughly 200 Hz when hitting or touching the bows accidently.

Because i don't have any "measurement head" for proper headphone measurements, to check if these (non damped) steel bows produce any interferences (which would affect the sound and may distort linearities) i used REWs tone generator with sinus and "sweeped" over the areas where the bows sound is and i softly hit them with fingers to "tune" the oscillators to exact frequencies.

i was unable to produce any interferences even with bit louder signals / levels (which would usually not healthy for ears over longer times) - even on exact oscillator tunings around the bows resonance frequencies - means: ther was no change if i damp the bows by fingers or not.

SPL graph - OLLO Audio HPS-4

individual SPL graph (seems REW measurement software) of my OLLO Audio HPS-4 headphones


I like:

  • top sound (!)
  • very ergonomic (over hours)
  • robust capsule work
  • external cable
  • swappable soft rings (if getting old/damaged)

I less like:

  • golden (gold plated) adaptor - for electrochemical reasons such golden plugs are not standard in pro studios - but in the "high end hifi" scene this is "nice". But it seems to be a (screwable) standard adaptor which can be easily swapped.
  • "no" R/L marks on the phones - on the cable only, but only readable when the sign on the plug is moved outwards and on good lightning conditions (grey on silver).
  • the "noise" from the steel bows when tapping them (but could be damped easily by bit leather, tape or similiar.
  • the mids are present and exact, but slightly "distracted" within the large "bandwidth" - if you prefer / need mid focused headphones, you should have or "add" one to your arsenal, but they usually offer less wide bandwidth "linearity".


There are no real cons.


This are really nice and valuable tools. for me, the HPS-4 is the best mixing headphone in my arsenal which i use too in sound design.

I can recommend them to any audio pro which work similiar to me and to audiophile music consumers.

i would definitely buy them again...ß)

OLLO HPS-4 bag

included HPS-4 bag


official product pages
history and philosophy of OLLO Audio