OLLO Audio HPS S4
| 50 mm Dynamic Driver | American Walnut Wood |
? OLLO Audio HPS S4, an open-back headphone with wooden cups.
The OLLO HPS S4 are not the typical industrially manufactured headphone, instead this is a product made by hand in Slovenia by OLLO Audio.
The headphone features very large drivers with a diameter of 50mm and real American Walnut wood cups reinforced with metal back plates.
The OLLO HPS S4 were created as a versatile mixing headphone for professionals, that could be easily carried around and driven with any source to facilitate the OTG use for mixing.
Different to the OLLO HPS S4R, the S4 model is the open-back headphone from the brand under the Studio headphones category.
You can buy the OLLO Audio HPS S4 directly from OLLO Audio.
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OLLO Audio HPS S4 Review
Tests & Scores
A
Accessories & Packaging
From a packaging and accessories point of view, the OLLO HPS S4 is nearly indistinguishable from the S4R (closed-back)
The product comes inside a small square box that includes a detachable cable, a 6.35mm stereo adapter and a frequency response measurement with a QC certification.

8/10
CB
Cable
The cable of the OLLO HPS S4 uses 2.5mm mono connectors with a detachable design and a straight 3.5mm jack (on the source end)
The cable itself has silver metal details inline (such as the cable bifurcation) and a two-colored/two-material build. The section corresponding to the source end has a brown braided finish while the 2.5mm headphone’s cable end has a red, rubberized finish.
W
Weight
OLLO Audio HPS S4 weight in Ounces and OLLO Audio HPS S4 weight in grams.
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CQ
Construction Quality and Build
The OLLO HPS S4 is identical to the HPS S4R regarding build, aesthetics and construction quality.
In fact, the only 3 details that set them apart aesthetically are the perforated back plates on the cups of the HPS S4, a brown-colored headband PU leather with white stitches and red-colored inner cups instead of black.
The rest of the unit has the same metal headband rods, Walnut cups and general metal build with equally outstanding rugged and durable quality.
Both the S4 and the S4R were designed to be fully serviceable with home tools and replaced with DIY solutions or official replacement parts from OLLO Audio.

B
Bass & Sub Bass
The OLLO HPS S4 has similar mid-bass and sub-bass to the OLLO HPS S4R. Which is a rich and punchy personality that can handle nearly any track thrown at them.
Still, the upper-bass response and the bass/mids transitioning frequencies are, overall, more emphasized on the HPS S4 than on the S4R.
Oppositely to the nature of open-back headphones, the OLLO HPS S4 does not show a pronounced rolled-off sub-bass. Instead, this open headphones show a capable lower end that can get as deep as many closed back headphones – indeed, the HPS S4 shows the same mid, lower and sub bass response as the closed back sibling, the OLLO HPS S4R.
An EQ aimed to boost bass will allow the OLLO HPS S4 to turn into a much richer and bassier headphone with noticeably punchier response and a much deeper sub-bass.
8/10
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M
Mids & Vocals
The midrange of the OLLO HPS S4 shares a, somewhat, similar tuning to the S4R but can become partially more congested at times were upper-bass is boosted.
Nonetheless, the OLLO HPS S4 has a warmer tint than the S4R while preserving a similarly laid back but not too distant male vocals personality.
Higher mids exhibit a bit less-emphasized tuning than the S4R, which adds up to the warmer and busier feel on them.
Users should expect smooth male vocals and no harshness at all coming from the OLLO HPS S4, thanks to the more relaxed upper mids that makes easier for them to avoid suffering from harsh peak issues.
Using an EQ showed a superb potential to “reorganize” the midrange of the HPS S4 with a cleaner and much less-congested vocals and lower mids, without eliminating it’s smoothness.
8/10

H
Highs & Treble
Due to the more emphasized upper-bass/lower-mids tuning, the OLLO HPS S4 gains a “fuller” but also bit darker highs feel.
On the other hand, the HPS S4 can resolve marginally more detail than the OLLO HPS S4R.
Similar to the upper mids, the S4 versus the S4R has a more rolled-off/”relaxed” lower-highs tuning that makes it, also, less fatiguing with no risk of sibilance and much less-frequent piercing peaks.
An EQ can remarkably open up the highs of the HPS S4 and allow them to become a competently more resolving headphone.
8/10

SL
Sound Leak
As expected with any open-back headphones, the leakage of the OLLO HPS S4 is very high and will be heard by anyone nearby.
This is the normal way an open-back headphone performs and seeing it happen is actually a positive confirmation that the headphone truly has an efficient open back.
3/10
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SI
Sound Isolation
Unexpectedly, the OLLO HPS S4 has a much stronger isolation than most open back headphones and even than less-isolating closed-back headphones.
7.75/10
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C
Comfort
The OLLO Audio HPS S4 shares the same small size of the HPS S4R, which makes it a full-sized, over-ear headphones with particularly tiny foot print.
Nonetheless, the brand has not sacrificed comfort nor fit on the HPS S4, being able to sport 90mm earpads with the right amount of cup’s depth to fit most ears without becoming uncomfortable.
The self-adjusting headband combined with it’s light-weighted metal frame and wide artificial leather band result in a remarkably comfortable open-back headphone to wear for hours.
Identically to the S4R, the HPS S4 has fully rotational cups and partially tiltable movements while the unit can, also, lay fully flat to reduce the size of the unit when being transported or stored.
8.75/10
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EQ
Response to Equalization
With (most probably) the same 50mm drivers on both the S4R and S4, the OLLO HPS S4 also showed an extraordinary response to EQ that can enable users to retune or fine-tune it’s original out-of-the-box sound signature and response with ease, while showing remarkable results.

At the same time, most of the EQ paths applied (carefully and wisely applied) did not empower any undesired sound qualities.
8.75/10
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SF
Size & Fit
OLLO Audio HPS S4 size and OLLO Audio HPS S4 fit.





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OLLO Audio HPS S4 Frequency Response Curve

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OLLO Audio HPS S4 Technical Specifications
Type | Dynamic |
---|---|
Driver Unit | 50mm |
Sensitivity | 112dB/mW |
Power Capacity | N/A |
Impedance | 32 ohms |
Frequency Response | 20-22,000Hz |
Diaphragm | Unknown |
Magnet | Unknown |
Cord | Y-type, round cord |
Plug | Stereo mini plug |
Weight | Approx. 328g |
Supplied Accessories | cable, pouch |
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OLLO Audio HPS S4 Scores
- Design - 8.75/108.8/10
- Bass - 8/108/10
- Mids - 8/108/10
- Highs - 8/108/10
- Comfort - 8.75/108.8/10
- Response to EQ - 8.75/108.8/10
- Value for Money - 8/108/10
Summary
NOTE: Being an open-back headphone, both the "Sound Leak" and "Sound Isolation" scores are not weighted for the Averaged score.
✅ Warm and pleasing sound
✅ Particularly deep sub-bass for an open-back headphone
✅ No harsh peaks
✅ No fatiguing sound
✅ Excellent build quality
✅ Very responsive to EQ
✅ Small foot print for an over-ear, open headphone
✅ Walnut wood cups
✅ Easily serviceable
✅ Detachable cable
✅ Handmade
✅ Very comfortable
❌ The headband’s rods will vibrate when touched and be heard when wearing the headphone
❌ Not purchasable on mainstream online shops
The OLLO HPS S4R can offer most of the benefits of the OLLO HPS S4, conserving the smooth and pleasing sound signature style but with a bit warmer, a more relaxed sound and an open-back design.
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